Author(s): Rong, MZ; Zhang, MQ; Ruan, WH
Title: Surface modification of nanoscale fillers for improving properties of polymer nanocomposites: a review
Source: MATERIALS SCIENCE AND TECHNOLOGY, 22 (7): 787-796 JUL 2006
Abstract: Direct incorporation of inorganic nanoscale building blocks into polymers represents a typical way for preparing polymeric nanocomposites. The most important aspect in preparation of nanocomposites through dispersive blending is surface modification of the nanofillers. It is able to increase hydrophobicity of the fillers, enhance interfacial adhesion via chain entanglement or chemical bonding and eliminate the loosen structure of filler agglomerates. The present paper reviews the state of the art of nanoparticles/polymer composites, including the specific surface pretreatment techniques and their applications. Especially, the role of treated nanoparticles and the mechanisms involved in the improvement of mechanical properties and wear resistance of the composites are highlighted.
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Record 2 of 83
Author(s): Dong, QQ; Zheng, Q; Zhang, MQ
Title: Studies on the morphology and the thermal properties of high-density polyethylene filled with graphite
Source: JOURNAL OF MATERIALS SCIENCE, 41 (10): 3175-3178 MAY 2006
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Record 3 of 83
Author(s): Zhang, B; Fu, RW; Zhang, MQ; Dong, XM; Wang, LC; Pittman, CU
Title: Gas sensitive vapor grown carbon nanofiber/polystyrene sensors
Source: MATERIALS RESEARCH BULLETIN, 41 (3): 553-562 MAR 9 2006
Abstract: A new class of conductive composites with good gas sensitivity was fabricated by filling polystyrene with vapor grown carbon nanofibers (VGCNF). A solution mixing/solvent removal procedure was used. VGCNFs form conductive networks at fiber loadings above the percolation limit within the matrix. Greatly improved conductivity is achieved relative to the same volume fraction of carbon black addition when these fibers are distributed to give reasonably uniform dispersions in the matrix. The high aspect ratios of these fibers (similar to 70-250 mn diameters and 5-75 mu m lengths) assist in forming low wt.% percolation thresholds (below 1 wt.% fiber). Excellent gas sensitivity with 10(4)-10(5) times higher than the original resistance value in many saturated organic vapors and a maximum resistance response of about 1.1 x 10(5) times exposure to saturated THF vapor at 6.25 wt.% of VGCNF in the polystyrene matrix was observed. The maximum resistance response declined from about 2.0 x 10(5) times at 15 degrees C to about 3.4 x 10(4) times at 55 degrees C. These composites exhibited stable and reusable gas sensitivity to THF vapor. Carbon black/polystyrene composites exhibit a negative vapor coefficient (NVC) upon swelling caused by filler redistribution. In contrast, VGCNF/polystyrene composites are more stable, with much smaller NVC values due to their high aspect ratios and reinforcing effects which stabilize electrical percolation pathways. Thus, VGCNF/organic polymer composites are good gas sensor candidates for detecting organic vapors. (c) 2005 Elsevier Ltd. All rights reserved.
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Record 4 of 83
Author(s): Chen, SG; Hu, JW; Zhang, MQ; Rong, MZ; Zheng, Q
Title: Improvement of gas sensing performance of carbon black/waterborne polyurethane composites: Effect of crosslinking treatment
Source: SENSORS AND ACTUATORS B-CHEMICAL, 113 (1): 361-369 JAN 17 2006
Abstract: When carbon black (CB) filled waterborne polyurethane (WPU) composites are exposed to organic solvent vapors, electrical resistance of the materials increases rapidly. They can thus serve as gas sensors. To improve the composites' performance for practical applications, crosslinking agent was added to the composite latexes, forming intra-molecular crosslinked networks among the matrix polymer of the composites. The method greatly increased the filler/matrix interfacial interaction and reduced the mobility of CB particles. In the composites that had absorbed solvent vapors, reconstruction of conduction paths through re-aggregation of the disconnected filler particulates became difficult. As a result, the unwanted negative vapor coefficient (NVC) effect was significantly weakened, while the gas sensitivity and the performance reproducibility were enhanced as well. (c) 2005 Elsevier B.V. All rights reserved.
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Record 5 of 83
Author(s): Ji, QL; Zhang, MQ; Rong, MZ; Wetzel, B; Friedrich, K
Title: Friction and wear of epoxy composites containing surface modified SiC nanoparticles
Source: TRIBOLOGY LETTERS, 20 (2): 115-123 OCT 2005
Abstract: The authors of the present paper evaluated the sliding wear behaviors of epoxy and its composites filled with untreated and treated SiC nanoparticles. The experimental results indicate that the nanoparticles pretreated by graft polymerization of polyacrylamide effectively improved the overall performance of the matrix epoxy. In comparison with the untreated SiC nanoparticles, the grafted SiC nanoparticles led to more significant reduction in frictional coefficient and wear rate of epoxy. Even under high contact pressure, the composites with grafted SiC nanoparticles possessed the highest wear resistance. The strong interfacial bonding between the grafted SiC nanoparticles and the matrix should account for the properties enhancement. Accordingly, a feasible way of efficiently applying SiC nanoparticles to the preparation of wear resisting nanocomposites has been developed.
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Record 6 of 83
Author(s): Zhang, MQ; Rong, MZ; Lu, X
Title: Fully biodegradable natural fiber composites from renewable resources: All-plant fiber composites
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 65 (15-16): 2514-2525 Sp. Iss. SI DEC 2005
Abstract: Wood flour can be converted into thermoplastics through proper benzylation treatment, which introduces large benzyl group onto cellulose and partially deteriorates the ordered structure of the crystalline regions. By changing a series of parameters, like reaction temperature, concentration of aqueous caustic solution, species of phase transfer catalyst, etc., the extent of benzyl substitution is regulated within a wide range so that a balanced thermal formability and mechanical performance of the modified wood flour is obtained. By using the properly plasticized China fir sawdust as the matrix, both discontinuous and continuous sisal fibers are compounded to produce composites from renewable resources, respectively. These all-plant fiber composites are characterized by moderate mechanical properties and full biodegradability, and might act as alternative to petro-based materials in terms of structural applications. (c) 2005 Elsevier Ltd. All rights reserved.
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Record 7 of 83
Author(s): Zhang, B; Fu, RW; Zhang, MQ; Dong, XM; Lan, PL; Qiu, JS
Title: Preparation and characterization of gas-sensitive composites from multi-walled carbon nanotubes/polystyrene
Source: SENSORS AND ACTUATORS B-CHEMICAL, 109 (2): 323-328 SEP 14 2005
Abstract: In this paper, a new kind of conductive polymer composites was fabricated by in situ polymerization of styrene (PS) in the presence of multi-walled carbon nanotubes (MWCNTs) and solution mixing of polystyrene with MWCNTs, respectively. The electrical percolation behaviors of the composites and their resistance responsivities against various organic vapors were investigated. The experimental results showed that the in situ polymerization method has more advantages to improve the dispersion of MWCNTs in PS matrix, and produces composites with high sensitivity and rate of response for the vapors of good solvents of PS at filler range from 5 to 15 wt.%. A rise in testing temperature raised the rate of response but lowered the maximum responsivity of the composites. It can be concluded that the MWCNT/PS composites developed in the present work are promising candidates for gas sensors to detect, distinguish and quantity organic vapors. (C) 2005 Elsevier B.V All rights reserved.
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Record 8 of 83
Author(s): Dong, QQ; Zheng, Q; Du, M; Zhang, MQ
Title: Temperature-dependence of dynamic rheological properties for high-density polyethylene filled with graphite
Source: JOURNAL OF MATERIALS SCIENCE, 40 (13): 3539-3541 JUL 2005
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Record 9 of 83
Author(s): Chen, SG; Hu, JW; Zhang, MQ; Rong, MZ; Zheng, Q
Title: Time dependent percolation of carbon black filled polymer composites in response to solvent vapor
Source: JOURNAL OF MATERIALS SCIENCE, 40 (8): 2065-2068 APR 2005
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Record 10 of 83
Author(s): Dong, MM; Fu, RW; Zhang, MQ; Zhang, B; Rong, NZ
Title: Organic vapour sensor from carbon black filled amorphous polymer composite: Effects of processing, carbon fibres and irradiation
Source: POLYMERS & POLYMER COMPOSITES, 13 (3): 213-221 2005
Abstract: Carbon black filled poly(butyl methacrylate) (CB/PBMA) composites as organic vapour sensors were fabricated by polymerization filling. The results indicate that the composites have a wide synthesis window, giving composite materials with high gas sensitivity under different conditions. In comparison with composites made by solution mixing, the composites made by polymerization filling have much higher responsivity to organic vapours because of the superior distribution of the filler particles. The addition of a third component, vapour-grown carbon fibres (VGCF), and the post-treatment of the composites by gamma-ray irradiation proved to be rather effective in enhancing response stability.
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Record 11 of 83
Author(s): Luo, Y; Rong, MZ; Zhang, MQ
Title: Covalently connecting nanoparticles with epoxy matrix and its effect on the improvement of tribological performance of the composites
Source: POLYMERS & POLYMER COMPOSITES, 13 (3): 245-252 2005
Abstract: Graft polymerization of glycidyl methacrylate onto nano-SiC particles by means of soapless emulsion polymerization results in composite particles consisting of SiC core and polymeric shell, in which polyglycidyl methacrylate (PGMA) is bonded to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. Compared with untreated nano-SiC particles, the grafted versions exhibit improved dispersibility. Besides, they are able to establish chemical bonding between the fillers and matrix through the reaction between the epoxide groups and the curing agent when being compounded with epoxy. As a result of these. advantages, the epoxy composites filled with PGMA grafted nano-SiC particles possess rather high sliding wear resistance and low frictional coefficient at low filler loading, which cannot be observed in untreated SiC nanoparticles/epoxy system.
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Record 12 of 83
Author(s): Ma, CG; Rong, MZ; Zhang, MQ; Friedrich, K
Title: Irradiation-induced surface graft polymerization onto calcium carbonate nanoparticles and its toughening effects on polypropylene composites
Source: POLYMER ENGINEERING AND SCIENCE, 45 (4): 529-538 APR 2005
Abstract: Nano-sized calcium carbonate was pretreated with silane coupling agent and then mixed with butyl acrylate that is of larger amount than the nanoparticles. Under gamma-irradiation, graft polymerization occurred on the nanoparticle surface, forming a nanocomposite structure consisting of grafted poly(butyl acrylate) (PBA), homopolymerized PBA, and the segregated nanoparticles. It was found that the silane pretreatment significantly promoted the graft reaction. When the grafted nano-CaCO3 particles were melt compounded with polypropylene (PP), an obvious synergistic effect, offered by (i) the chemical bonding between the elastomer type grafted PBA and nano-CaCO3 and (ii) the deliberately introduced thick interlayer mainly constructed by the homopolymerized PBA, led to a significant increase in notch impact strengths and elongation to break of PP at a rather low content of nano-CaCO3. Meanwhile, the tensile stiffness of the composites was also slightly increased and the yielding strength of the composites was almost unchanged. The results are different from those with conventional rubber-toughened plastics, in which the improvement of ductility is acquired at high additive fraction and a great expense of strength performance. (c) 2005 Society of Plastics Engineers.
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Record 13 of 83
Author(s): Chen, SG; Hu, JW; Zhang, MQ; Rong, MZ
Title: Effects of temperature and vapor pressure on the gas sensing behavior of carbon black filled polyurethane composites
Source: SENSORS AND ACTUATORS B-CHEMICAL, 105 (2): 187-193 MAR 28 2005
Abstract: The authors of the present work developed conductive composite materials comprised of carbon black and waterbome polyurethane by latex blending. Unlike conventional polymer composites that only respond to certain specific group of solvent vapors, the present composites exhibit electrical resistance responses to a series of vapors of polar and non-polar solvents as a result of the block molecular structure of polyurethane. Under a given vapor pressure, the response rate increases with increasing temperature, but the maximum magnitude of response of the composites decreases because of the effect of vapor desorption. In the case of a constant temperature, the maximum responsivity of the composites increases with a rise in vapor pressure and the relationship follows linear regression within the p/p degrees range of 10(-4) to 2 x 10(-2). Besides, the slopes of the linear dependences vary when the vapor species is changed, suggesting the possibility of quantifying and distinguishing vapors. (c) 2004 Elsevier B.V. All rights reserved.
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Record 14 of 83
Author(s): Wu, CL; Zhang, MQ; Rong, MZ; Friedrich, K
Title: Silica nanoparticles filled polypropylene: effects of particle surface treatment, matrix ductility and particle species on mechanical performance of the composites
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 65 (3-4): 635-645 MAR 2005
Abstract: The current paper is a continuation of the authors' work on mechanical performance of nano-silica/polypropylene (PP) composites. Unlike the fumed nano-silica used in the previous studies, precipitated nano-silica is employed in the present investigation. The results indicate that graft polymerization onto the precipitated nano-silica (that has been successfully applied to the surface modification of fumed nano-silica) is still an effective method to pre-treat the particles, which leads to an overall improvement of the composites properties. In addition to the grafting polymers covalently attached to the nanoparticles, matrix ductility and nanoparticles size are important factors that influence the extent of performance enhancement of the composites. In the case of suitable combination of these factors, the positive effect of the nanoparticles can be maximized. (C) 2004 Elsevier Ltd. All rights reserved.
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Record 15 of 83
Author(s): Ji, QL; Zhang, MQ; Rong, MZ; Wetzel, B; Friedrich, K
Title: Tribological properties of surface modified nano-alumina/epoxy composites
Source: JOURNAL OF MATERIALS SCIENCE, 39 (21): 6487-6493 NOV 1 2004
Abstract: Nano-sized Al2O3 particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites. Curing habit, mechanical properties and tribological performance revealed by sliding wear tests of the composites were investigated. The experimental results indicated that the nanoparticles accelerate curing of epoxy, increase composites' impact strength and decrease wear rate and frictional coefficient of the composites. The surface modification by means of grafting polymerization can further enhance the properties improvement of epoxy due to the increased filler/matrix interfacial interaction. Compared to frictional coefficient, wear rate of epoxy can be decreased more remarkably by the addition of nano-alumina when rubbing against steel. The wear mode changes from severe peeling off of unfilled epoxy to mild micro-ploughing in the case of nano-alumina filled composites. (C) 2004 Kluwer Academic Publishers.
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Record 16 of 83
Author(s): Zhang, MQ; Rong, MZ; Zhang, ZW
Title: Organic vapor sensibility of carbon black/polyethylene wax composites
Source: JOURNAL OF MATERIALS SCIENCE, 39 (16-17): 5617-5620 AUG-SEP 2004
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Record 17 of 83
Author(s): Hu, JW; Chen, SG; Zhang, MQ; Li, MW; Rong, MZ
Title: Low carbon black filled polyurethane composite as candidate for wide spectrum gas-sensing element
Source: MATERIALS LETTERS, 58 (27-28): 3606-3609 NOV 2004
Abstract: To reduce the amount of carbon black and to broaden the applicability of conductive polymer composites serving as gas sensors, polyurethane-based composite was prepared by latex blending. The composite has very low electrical threshold and hence provides improved processability. In the environment of organic solvent vapors, the composite with 3.5 wt.% of carbon black exhibits significant increase of its electrical resistance regardless of the solvents' polarities and the maximum variation in resistance decreases linearly with decreasing vapor concentration. Besides, the slopes of the linear dependences change with the solvent species, which might allow quantifying vapor concentration and species. The measurable vapor concentrations of the composite are lower than or equal to the Chinese standard of exposure limits. Besides, the composite also shows high reproducibility as evidenced by over 5000 times of repeated sensing tests. It is believed that the composite can be used in gas sensor arrays with much smaller sizes and wide sensitivity. (C) 2004 Elsevier B.V. All rights reserved.
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Record 18 of 83
Author(s): Dong, XM; Fu, RW; Zhang, MQ; Zhang, B; Rong, MZ
Title: Electrical resistance response of carbon black filled amorphous polymer composite sensors to organic vapors at low vapor concentrations
Source: CARBON, 42 (12-13): 2551-2559 2004
Abstract: Electrical resistance responses of amorphous polymer composites against various organic vapors at low concentrations are investigated by using polymerization-filling fabricated carbon black/poly(butyl methacrylate) (CB/PBMA) system as the model material. The experimental results indicate that the composites have high selectivity to various organic vapors at the same concentration. In addition, the electric resistance response of the composites against organic vapors takes place in step with their vapor adsorption procedure. It is demonstrated that uptake of solvent vapors in the matrix polymer guarantees the increase in a composite's resistance over a wide range of vapor concentration. According to these findings, the composites can be used as an organic vapor sensor to detect, quantify and discriminate various organic vapors. Unlike the case of saturated vapors, similarity between the solubility parameters of the matrix polymer and a solvent can no longer serve as a criterion to predict the response of the composite against the low concentration solvent gas. (C) 2004 Elsevier Ltd. All rights reserved.
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Record 19 of 83
Author(s): Wu, CL; Zhang, MQ; Rong, MZ; Lehmann, B; Friedrich, K
Title: Functionalisation of polypropylene by solid phase graft polymerisation and its effect on mechanical properties of silica nanocomposites
Source: PLASTICS RUBBER AND COMPOSITES, 33 (2-3): 71-76 2004
Abstract: To prepare macromolecular compatibiliser for grafted nano-SiO2/polypropylene (PP) composites, solid phase graft copolymers of PP with styrene and ethyl acrylate were synthesised, respectively. It was found that both per cent grafting and grafting efficiency can be adjusted by changing initiator concentration, reaction temperature and reaction time. As a result of partial chain scission and deterioration of ordered structure of PP during the graft polymerisation, the grafted PP exhibits poorer thermal stability and crystallisability than the unmodified PP. Mechanical tests of grafted nano-SiO2/PP composites indicated that the addition of PP copolymer with the same species of grafting polymer as that on the nanoparticles further improves the ductility of the composites. Molecular rigidity of the grafting polymers, presence of the homopolymer produced during the graft polymerisation, and strain rate of the load applied have an important influence on the toughening effect of the functionalised PP.
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Record 20 of 83
Author(s): Hou, YH; Zhang, MQ; Rong, MZ
Title: Thermally induced performance decay in conductive polymer composites
Source: POLYMER COMPOSITES, 25 (3): 270-279 JUN 2004
Abstract: In the course of long-term service, electrically conductive polymer composites acting as positive temperature coefficient (PTC) materials are faced with performance decay characterized by gradually increased room temperature resistivity and decreased PTC intensity. To reveal the influencing factors and to find appropriate ways for solving the problems, thermal-cold cycling experiments (which simulate the extreme operating conditions of PTC type materials in a laboratory environment) and electrification tests are carried out in the current work. The results demonstrate that irreversible damage of partial conductive networks and, in particular, oxidation degradation induced crystallizability deterioration of the matrix polymer are responsible for the electrical performance decay. Additionally, an increase in the contact resistance formed at the metallic electrode/composite contacts exerts a negative influence on the service life of the composites. (C) 2004 Society of Plastics Engineers.
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Record 21 of 83
Author(s): Wu, CL; Zhang, MQ; Rong, MZ; Lehmann, B; Friedrich, K
Title: Functionalisation of polypropylene by solid phase graft polymerisation and its effect on the mechanical properties of silica nanocomposites
Source: PLASTICS RUBBER AND COMPOSITES, 32 (10): 445-450 2003
Abstract: To prepare macromolecular compatibiliser for grafted nano-SiO2/polypropylene (PP) composites, solid phase graft copolymers of PP with styrene and ethyl acrylate were synthesised, respectively. It was found that both percentage grafting and grafting efficiency can be adjusted by changing initiator concentration, reaction temperature and reaction time. Due to partial chain scission and deterioration of the ordered structure of PP during the graft polymerisation, the grafted PP exhibits worse thermal stability and crystallisability than the unmodified PP Mechanical tests of grafted nano-SiO2/PP composites indicated that the addition of PP copolymer with the same species of grafting polymer as that on the nanoparticles further improves the ductility of the composites. Molecular rigidity of the grafting polymers, presence of the homopolymer produced during the graft polymerisation, and strain rate of the load applied have important influences on the toughening effect of the functionalised PP.
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Record 22 of 83
Author(s): Lu, J; Zhang, MQ; Rong, MZ; Yu, SL; Wetzel, B; Friedrich, K
Title: Thermal stability of frictional surface layer and wear debris of epoxy nanocomposites in relation to the mechanism of tribological performance improvement
Source: JOURNAL OF MATERIALS SCIENCE, 39 (11): 3817-3820 JUN 1 2004
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Record 23 of 83
Author(s): Ruan, WH; Zhang, MQ; Rong, MZ; Friedrich, K
Title: Mechanical properties of nanocomposites from ball milling grafted nano-silica/polypropylene block copolymer
Source: POLYMERS & POLYMER COMPOSITES, 12 (4): 257-267 2004
Abstract: Nanocomposites consisting of ethylene-propylene block copolymer filled with nanosilica (pre-treated by ball milling aided graft polymerisation) were prepared by a conventional compounding technique. The mechanical performance of the nanocomposites and the morphological changes induced by the addition of the nanoparticles were investigated. It was confirmed that the copolymer chains were chemically bonded to the silica particles during mechanochemical grafting in the ball mill. Morphology observations revealed that strong interfacial interaction between the grafting polymer (i.e., poly(butyl acrylate)) and the matrix (i.e., ethylene-propylene block copolymer) is critical for bringing the reinforcing effect of the nanoparticles into play. Owing to the enhanced interfacial interaction, the grafted nanoparticles exhibited a nucleating effect and improved the crystallinity of the polymer matrix. In addition, the particles also had a toughening effect on the amorphous polypropylene phase because of entanglements between the grafting polymer and the matrix. Insufficient interaction between the nanoparticles and ethylene-propylene rubber phase of the copolymer matrix actually introduces restraints. As a result, the tensile strength and modulus of the nanocomposites can be significantly increased by using low loadings of the treated nanoparticles. The decrease in the notched Charpy impact strength was insignificant in comparison to that of conventional micron-scale inorganic particles filled composites. The technical route proposed is therefore feasible for fabricating polymer composites with inorganic nanoparticles.
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Record 24 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Yue, DL; Yang, GC
Title: The preparation of self-reinforced sisal fiber composites
Source: POLYMERS & POLYMER COMPOSITES, 12 (4): 297-307 2004
Abstract: To prepare self-reinforced sisal composites, sisal fibers were cleaned, treated with NaOH solution, and then benzylated with benzyl chloride. In this way, the skin layers of the fibers were converted into thermoplastic material while the core of the fiber cells remained unchanged. Under the circumstances of hot pressing, self-reinforced all-plant fiber composites of sisal can be prepared, in which plasticised sisal serves as matrix and the unplasticised cores of the fibers as reinforcement. In this work the effect of the reaction conditions, such as alkalinity, temperature and the extent of benzylation, was studied in detail. The roles of quaternary ammonium salts and gamma- ray irradiation treatment on the efficiency of benzylation were also taken into account. In addition, structural characteristics, melt flow and mechanical properties of the modified sisal and their composite sheets were analysed. It was found that a balance between melt processability and the reinforcing effect of the benzylated sisal fibers was required.
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Record 25 of 83
Author(s): Shi, G; Zhang, MQ; Rong, MZ; Wetzel, B; Friedrich, K
Title: Sliding wear behavior of epoxy containing nano-Al2O3 particles with different pretreatments
Source: WEAR, 256 (11-12): 1072-1081 JUN 2004
Abstract: The sliding wear performance of epoxy composites filled with nano-sized Al2O3 particles was studied in the present paper. To enhance the interfacial interaction between the fillers and the matrix polymer, the nanoparticles were pretreated by either silane coupling agent or graft polymerization. The experimental results indicated that the frictional coefficient and wear rate of epoxy can be reduced at rather low concentration of nano-Al2O3, and the pretreatments of the particles further gave play to this favorable effect. The lowest specific wear rate, 1.6 x 10(-6) mm(3)/Nm, is observed for the composites with 0.24 vol.% nano-Al2O3 grafted by polyacrylamide, which is decreased by 97% as compared to the value of unfilled epoxy. Although the incorporation of nano-Al2O3 particles leads to increased flexural modulus and flexural strength of epoxy, the wear performance of the composites does not correlate with these static mechanical properties. In contrast, there is a positive correlation between wear resistance and impact strength (i.e. increase in impact strength correlates with a decrease in specific wear rate). (C) 2003 Elsevier B.V. All rights reserved.
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Record 26 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Yue, DL; Yang, GC
Title: Environmental degradability of self-reinforced composites made from sisal
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 64 (9): 1301-1310 JUL 2004
Abstract: S elf-rei it forced sisal composites were prepared by molding slightly benzylated sisal fibers. The environmental degradation behavior of the materials was evaluated in the present paper with reference to the effects of ageing in water, enzyme solution and soil, respectively. It was found that the inherent biodegradability of plant fibers is still associated with the composites. In contrast to plant fiber/synthetic polymer composites, however, water resistance of the current composites is greatly increased as characterized by the insignificant variation in the mechanical properties of the composites before and after being aged in water. With the help of cellulase and fungi, the self-reinforced sisal composites can be degraded leading to weight loss and decay of mechanical performance. In the course of cellulase induced degradation, the insusceptibility of lignin to the enzyme decelerated the rate of deterioration, while the soil burial resulted in an overall decomposition of the composites. (C) 2003 Elsevier Ltd. All rights reserved.
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Record 27 of 83
Author(s): Rong, MZ; Zhang, MQ; Liang, HC; Zeng, HM
Title: Surface derivatization of nano-CdS clusters and its effect on the performance of US quantum dots in solvents and polymeric matrices
Source: APPLIED SURFACE SCIENCE, 228 (1-4): 176-190 APR 30 2004
Abstract: Synthesis of nanometer-sized clusters of CdS in inverse-micellar solution and in situ chemical derivatization of the surface of these cluster compounds were studied in the current paper. The nanoparticle surface can be terminated and passivated by the addition of imidazole and thiol molecules, which allows of inhibiting the particle from agglomeration, improving particle distribution in organic solvents and polymer matrices, and blocking surface defects that cause radiationless recombination of charge carriers. The solubility of these re-dispersible powders in different solvents was studied, and then the CdS quantum dots-polymer composites were prepared using solution mixing method. By means of optical, structural and thermal characterization techniques, the particle distribution and interfacial interaction in the composite systems and their influence on the properties of quantum CdS were revealed in detail. (C) 2004 Elsevier B.V. All rights reserved.
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Record 28 of 83
Author(s): Ruan, WH; Zhang, MQ; Rong, MZ; Friedrich, K
Title: Polypropylene composites filled with in-situ grafting polymerization modified nano-silica particles
Source: JOURNAL OF MATERIALS SCIENCE, 39 (10): 3475-3478 MAY 15 2004
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Record 29 of 83
Author(s): Dong, XM; Qin, ZP; Fu, RW; Zhang, MQ; Zhang, B; Rong, MZ
Title: Percolation and gas sensing behaviours of ternary conductive composites: Vapour-grown carbon fibres carbon black/poly(methyl methacrylate)
Source: ADVANCED COMPOSITES LETTERS, 12 (6): 247-253 2003
Abstract: To reduce the dosage of carbon black (CB) in conductive polymer composites, vapour-grown carbon fibre (VGCF) were incorporated in the present work. The experimental results indicated that only small amount of VGCF is sufficient to significantly improve the conductivity of the composites based on poly(methyl methacrylate) (PMMA), as characterized by an additional percolation process. Besides, the ternary composites exhibit electrical responsivity to saturated ethyl acetate vapour as high as 101 in association with good reproducibility. In comparison to CB/PMMA composites having the same filler loading, VGCF/CB/PMMA composites provide higher response rate and recoverability.
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Record 30 of 83
Author(s): Chen, SG; Hu, JW; Zhang, MQ; Li, MW; Rong, MZ
Title: Gas sensitivity of carbon black/waterborne polyurethane composites
Source: CARBON, 42 (3): 645-651 2004
Abstract: The synthesis of conductive composites consisting of waterborne polyurethane (WPU) and carbon black (CB) is reported. Besides the low percolation threshold (0.7-0.95 wt%), the composites are quite sensitive to organic solvent vapors regardless of their polarities as characterized by the drastic changes in conductivity. In the case of polar solvents, negative and positive vapor coefficient phenomena of the composites were successively observed with a rise in CB content. It was found that different mechanisms are responsible for the broad applicability of the composites as candidates for gas sensing materials owing to the different interactions among the matrix polymer, the filler particles and the solvent molecules. (C) 2004 Elsevier Ltd. All rights reserved.
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Record 31 of 83
Author(s): Wu, CL; Zhang, MQ; Rong, MZ; Lehmann, B; Friedrich, K
Title: Deformation characteristics of nano-SiO2 filled polypropylene composites
Source: POLYMERS & POLYMER COMPOSITES, 11 (7): 559-562 2003
Abstract: Surfaces of nano-silica particles can be effectively modified by means of irradiation graft polymerization. When polypropylene (PP) was compounded with these treated nanoparticles, an overall improvement in the mechanical properties of the composites at rather low filler content was acquired. The present work observed the deformation characteristics of the PP nanocomposites using transmission electron microscope. Due to the interfacial entanglement between the grafting polymers attached to the nanoparticles and the matrix polymer, the grafted nano-SiO2 exhibits much greater extensibility in the composites than the nanoparticles as-received. It is believed to be the main cause of extensive plastic drawing of the matrix polymer surrounding the treated nanoparticles, and it provides the composites with higher static ductility.
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Record 32 of 83
Author(s): Li, JR; Xu, JR; Zhang, MQ; Rong, MZ
Title: Carbon black/polystyrene composites as candidates for gas sensing materials
Source: CARBON, 41 (12): 2353-2360 2003
Abstract: Amorphous polymer-based composites consisting of polystyrene and carbon black were developed in the current work as candidates for gas sensing materials. With the help of polymerization filling, i.e., in-situ polymerization of styrene in the presence of carbon black, the composites were provided with low percolation threshold. The experimental results indicated that the composites have selective sensitivity as characterized by high electrical responsivity to the vapors of non-polar and low polar solvents, and low responsivity to high polar solvent vapors as well. Besides conductivity of the composites, absorption characteristics of both the matrix and the fillers exert importance influence on the gas sensitivity of the composites. Therefore, composites' performance can be tailored by changing filler concentration, molecular weight and molecular weight distribution of matrix polymer, etc. In regard to the fact that most conducting polymer composites as vapor sensing materials are based on crystalline polymer matrices, the approach reported by this paper provides another feasible way to develop new candidates. (C) 2003 Elsevier Ltd. All rights reserved.
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Record 33 of 83
Author(s): Liang, HC; Rong, M; Zhang, MQ; Zeng, HM; Xiang, H; Wang, SF; Gong, QH
Title: Highly filled Nano-CdS/polystyrene nanocomposite film with self-organization behavior
Source: POLYMERS & POLYMER COMPOSITES, 11 (6): 441-448 2003
Abstract: Highly filled polystyrene (PS) composite film with a nano-CdS loading of 20wt.% can be obtained when a certain mercaptan is applied to the particles' surfaces. Because of a strong electron transfer interaction between the modified CdS nanoparticles and the aliphatic carbons in PS, self-organization of the nanoparticles is perceivable in the composites. As a result, the ultraviolet/visible absorption edge of the treated nano-CdS/ PS composites is blue-shifted in addition to the shift caused by quantum size effect. The fluorescence emission peak is accompanied by some fine structures and becomes redshifted and narrower. Unlike conventional nanocomposites that generally contain low concentrations of nanoparticles (less than 10wt.%), the present approach greatly improves the scope for cooperative behavior of the nanoparticles.
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Record 34 of 83
Author(s): Wetzel, B; Haupert, F; Zhang, MQ
Title: Epoxy nanocomposites with high mechanical and tribological performance
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 63 (14): 2055-2067 NOV 2003
Abstract: Small ceramic particles are known to enhance the mechanical and tribological properties of polymers. Introduced into an epoxy resin, the filler morphology, size, particle amount and the dispersion homogeneity influence extensively the composite's performance. In the present study, various amounts of micro- and nano-scale particles (calcium silicate CaSiO3, 4-15 mum, alumina Al2O3, 13 nm) were systematically introduced into an epoxy polymer matrix for reinforcement purposes. The influence of these particles on the impact energy, flexural strength, dynamic mechanical thermal properties and block-on-ring wear behavior was investigated. If the nanoparticles were incorporated only, they yield an effective improvement of the epoxy resin at a nanoparticle content of already 1-2 vol.% Al2O3. Choosing the nanocomposite with the highest performance Lis a matrix, conventional CaSiO3, microparticles were further added in order to achieve additional enhancements in the mechanical properties. In fact, synergistic effects were found in the form of a further increase in wear resistance and stiffness. Several reasons to explain these effects in terms of reinforcing mechanisms were discussed. (C) 2003 Elsevier Ltd. All rights reserved.
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Record 35 of 83
Author(s): Rong, MZ; Zhang, MQ; Shi, G; Ji, QL; Wetzel, B; Friedrich, K
Title: Graft polymerization onto inorganic nanoparticles and its effect on tribological performance improvement of polymer composites
Source: TRIBOLOGY INTERNATIONAL, 36 (9): 697-707 SEP 2003
Abstract: To overcome the disadvantages generated by the loosened nanoparticle agglomerates dispersed in polymer composites, a chemical grafting method was applied to modify nano-alumina, silicon carbide and silicon nitride through covalently introducing polyacrylamide (PAAM) onto the particles. Sliding wear tests demonstrated that the frictional coefficient and specific wear rate of the nanoparticles/epoxy composites are lower than those of unfilled epoxy. Grafted nanoparticles reinforced composites have the lowest frictional property and the highest wear resistance due to the strengthening of the nanoparticle agglomerates and the enhancement of filler/matrix interfacial interaction resulting from the grafting polymers. Comparatively, graft treatment of nanoparticles is more beneficial to the improvement of the tribological features of the composites than the silane treatment that is used conventionally. (C) 2003 Elsevier Science Ltd. All rights reserved.
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Record 36 of 83
Author(s): Dong, XM; Fu, RW; Zhang, MQ; Zhang, B; Rong, MZ
Title: Carbon black filled poly(2-ethylhexyl methacrylate) as a candidate for gas sensing material
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 22 (15): 1057-1059 AUG 1 2003
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Record 37 of 83
Author(s): Lehmann, B; Friedrich, K; Wu, CL; Zhang, MQ; Rong, MZ
Title: Improvement of notch toughness of low nano-SiO2 filled polypropylene composites
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 22 (14): 1027-1030 JUL 15 2003
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Record 38 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Shi, GA; Yang, GC
Title: All-plant fiber composites. II: Water absorption behavior and biodegradability of unidirectional sisal fiber reinforced benzylated wood
Source: POLYMER COMPOSITES, 24 (3): 367-379 JUN 2003
Abstract: Sisal fiber reinforced benzylated fir sawdust composites belong to a new category of composite materials, in which both the reinforcement and matrix are based on plant fibers, i.e. renewable resources. The present paper discusses the water absorption behavior of the composites and its influence on the mechanical properties of the composites. In addition, biodegradability of the composites is assessed by using enzyme and fungi tests, respectively. The experimental results indicate that water absorption behavior of the composites is mainly controlled by the reinforcing fiber and the fiber/matrix interfacial characteristics. The inherent biodegradability of the raw materials of the all-plant fiber composites proves to be retained. During the tests of enzymolysis and biodeterioration in soil, damage of the composites was initiated either inside the sisal fiber or at the surface of the composites.
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Record 39 of 83
Author(s): Shi, G; Zhang, MQ; Rong, MZ; Wetzel, B; Friedrich, K
Title: Friction and wear of low nanometer Si3N4 filled epoxy composites
Source: WEAR, 254 (7-8): 784-796 APR 2003
Abstract: To prepare epoxy-based composites with low frictional coefficient and high wear resistance, nanometer silicon nitride particles were added. Dry sliding wear tests indicate that the composite materials exhibit significantly improved tribological performance and mechanical properties at rather low filler content (typically less than 1 vol.%). Unlike the severe wear observed in unfilled epoxy dominated by fatigue-delamination mechanism, the wear mode of nano-Si3N4 composites is characterized by mild polishing. It is believed that strong interfacial adhesion between Si3N4 nanoparticles and the matrix, reduced damping ability and enhanced resistance to thermal distortion of the composites, and tribochemical reactions involving Si3N4 nanoparticles account for the reduced frictional coefficient and wear rate of the composites. (C) 2003 Elsevier Science B.V. All rights reserved.
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Record 40 of 83
Author(s): Dong, XM; Fu, RW; Zhang, MQ; Zhang, B; Li, JR; Rong, MZ
Title: Gas sensing materials from carbon black/poly(methyl methacrylate) composites
Source: POLYMERS & POLYMER COMPOSITES, 11 (4): 291-299 2003
Abstract: In this work, the electrical conductivity of carbon black/poly(methyl methacrylate) composites and its responsiveness to organic solvent vapors were investigated. The carbon black-polymer conducting composites were synthesized by in-situ polymerization. They exhibited a low electrical percolation threshold (similar to3.3wt% of carbon black). The electric resistance of the composites increased drastically by over 10(4) times when they were exposed to good solvent vapours such as chloroform, tetrahydrafuran and ethyl acetate, and it recovered when the composites were transferred to air. The effect of temperature on the vapour responsivity of the composites was notable. An elevated temperature accelerated the vapour-induced variation in electrical resistance of the composites. The experimental data also indicate that the composites possessed a good reproducibility of vapour responsivity. These results suggest that they can be regarded as promising gas sensors characterized by easy processability and cost effectiveness.
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Record 41 of 83
Author(s): Privalko, VP; Shumsky, VF; Privalka, EG; Karaman, VM; Walter, R; Friedrich, K; Zhang, MQ; Rong, MZ
Title: Viscoelasticity and flow behavior of irradiation grafted nano-inorganic particle filled polypropylene composites in the melt state
Source: JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, 137 (1-3): 208-213 JUN 30 2003
Abstract: Nanoparticles (mean size about 7 nm) of the standard pyrogenic Aerosil 1380 (Degussa) pregrafted by gamma-irradiation with styrene were melt-compounded with the general purpose isotactic polypropylene homopolymer to prepare four nanocomposites with filler volume contents up to 4.68%. Storage G'(omega) and loss G"(omega) shear moduli in the melt state (measured in the range of linear viscoelasticity at three temperatures in the frequency window spanning about three decades) were treated to derive the relaxation times spectra h(tau) using the NLREG computer program based on Tikhonov's method of non-linear regularization.
The experimental data were interpreted in terms of the tentative model highlighting the structural significance of the ratio of mean thickness of polymer interlayer between neighboring filler particles,
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Record 42 of 83
Author(s): Li, JR; Xu, JR; Zhang, MQ; Rong, MZ
Title: Electrical response to organic vapor of conductive composites from amorphous polymer/carbon black prepared by polymerization filling
Source: MACROMOLECULAR MATERIALS AND ENGINEERING, 288 (2): 103-107 FEB 20 2003
Abstract: In recent years, conductive polymer composites have found applications as gas sensors because of their sudden change in electric resistance of several orders of magnitude when the material are exposed to certain solvent vapors. However, the composite having this function reported so far are mostly based on crystalline polymeric matrices, which factually sets a limit to materials selection. The present work prepares polystyrene/carbon black composites through polymerization filling and proves that the amorphous polymer composites can also serve as gas sensing materials. The composites' percolation threshold is much lower than that of the composites produced by dispersive mixing. In addition, high responsivity to some organic vapors coupled with sufficient reproducibility is acquired. The experimental data show that molecular weight and molecular weight distribution of the matrix polymer and conducting filler content exert great influence on the electrical response behaviour of the composites. As a result, composites performance van be purposely tailored accordingly. Compared with the approaches of melt-blending and solution-blending, the current technique is characterized by many advantages, such as simplicity, low cost,. and easy to be controlled.
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Record 43 of 83
Author(s): Zhang, MQ; Rong, MZ; Zhang, HB; Friedrich, K
Title: Mechanical properties of low nano-silica filled high density polyethylene composites
Source: POLYMER ENGINEERING AND SCIENCE, 43 (2): 490-500 FEB 2003
Abstract: Modification of nanoparticles through graft polymerization is able to change the chemical nature of the particles' surfaces and provides an effective means for the preparation of nano-fillers specified for composites manufacturing. The present work focuses on the mechanical role of grafted nano-SiO2 particles in high density polyethylene composites prepared by melt compounding. The experimental results show that at a content of 0.75 vol%, the modified nano-silica results in a rise in tensile stiffness, tensile strength and impact strength of the composites. The grafted nanoparticles can improve the mechanical performance of the matrix polymer more effectively than the untreated version. In addition, a further enhancement of the composites stiffness and strength can be achieved by crosslinking the concentrated masterbatches, which has not yet been revealed in the authors' previous works on grafted nano-SiO2 particles/polypropylene composites. It is thus revealed that the introduction of the grafting polymers onto the nanoparticles increases the tailorability of the composites.
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Record 44 of 83
Author(s): Zhang, MQ; Rong, MZ; Pan, SL; Friedrich, K
Title: Tensile properties of polypropylene filled with nanoscale calcium carbonate particles
Source: ADVANCED COMPOSITES LETTERS, 11 (6): 293-298 2002
Abstract: To bring the positive effect of nanoscale calcium carbonate into play, macromolecular chains were introduced onto the particles by irradiation grafting polymerisation so that the hydrophobicity of the particles was increased and the loosen agglomerates became stronger. Tensile testing results demonstrated that polypropylene composites incorporated with the grafted nano-CaCO3 particles exhibited improved stiffness, strength and toughness at low filler content when proper grafting polymers are introduced. Species of grafting polymers adhered to the nanoparticles is an important factor affecting the modification effect of the matrix polymer. Therefore, composites performance can be purposely tailored accordingly.
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Record 45 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Shi, G; Yang, GC
Title: Self-reinforced melt processable composites of sisal
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 63 (2): 177-186 2003
Abstract: Through slight benzylation treatment, skin layers of sisal fibers were converted into thermoplastic material while the core of the fiber cells remained unchanged. On the basis of these modified sisal fibers, self-reinforced composites were prepared using hot pressing, in which the plasticized parts of sisal serve as matrix and the unplasticized cores of the fibers as reinforcement. The paper discussed the influence of various benzylation conditions on the structure, thermal flowability and mechanical properties of modified sisal and the composites. It was found that a balance of melt processability and reinforcing effect of the benzylated sisal fibers should be considered. Unlike the conventional plant fiber composites using petro-polymers as matrices, the current self-reinforced composites based on sisal are characterized by inherent interfacial compatibility and full biodegradability. (C) 2002 Elsevier Science Ltd. All rights reserved.
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Record 46 of 83
Author(s): Dong, XM; Fu, RW; Zhang, MQ; Zhang, B; Li, JR; Rong, MZ
Title: Vapor-induced variation in electrical performance of carbon black/poly (methyl methacrylate) composites prepared by polymerization filling
Source: CARBON, 41 (2): 371-374 2003
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Record 47 of 83
Author(s): Zhang, MQ; Rong, MZ; Yu, SL; Wetzel, B; Friedrich, K
Title: Effect of particle surface treatment on the tribological performance of epoxy based nanocomposites
Source: WEAR, 253 (9-10): 1086-1093 NOV 2002
Abstract: To overcome the disadvantages generated by the loosened nanoparticle agglomerates dispersed in polymer composites, an irradiation grafting method was applied to modify nanosilica by covalently bonding polyacrylamide (PAAM) onto the particles. When the grafted nanosilica was added to epoxy, the curing kinetics of the matrix was accelerated. Moreover, the grafting PAAM can take part in the curing of epoxy so that chemical bonding was established between the nanometer fillers and the matrix. Sliding wear tests of the materials demonstrated that the frictional coefficient and the specific wear rate of nanosilica/epoxy composites are lower than those of the unfilled epoxy. With a rise in nominal load, both frictional coefficient and wear rate of the composites decrease, suggesting a wear mechanism different from that involved in wearing of epoxy. Grafted nanosilica reinforced composites have the lowest frictional property and the highest wear resistance of the examined composites. Compared with the cases of microsized silica and untreated nanosilica, the employment of grafted nanosilica provided the composites with much higher tribological performance enhancement efficiency. (C) 2002 Elsevier Science B.V. All rights reserved.
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Record 48 of 83
Author(s): Rong, MZ; Zhang, MQ; Wang, HB; Zeng, HM
Title: Surface modification of magnetic metal nanoparticles through irradiation graft polymerization
Source: APPLIED SURFACE SCIENCE, 200 (1-4): 76-93 NOV 15 2002
Abstract: To tailor the interfacial interaction in magnetic metal nanoparticles filled polymer composites, the surfaces of iron, cobalt and nickel nanoparticles were grafted by irradiation polymerization. In the current report, effects of grafting conditions, including irradiation atmosphere, irradiation dose and monomer concentration, on the grafting reaction are presented. The interaction between the nanoparticles and the grafted polymer was studied by thermal analysis and X-ray photoelectron spectrometry. It was found that there is a strong interfacial interaction in the form of electrostatic bonding in the polymer-grafted nanoparticles. The dispersibility of the modified nanoparticles in chloroform was significantly improved due to the increased hydrophobicity. (C) 2002 Elsevier Science B.V. All rights reserved.
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Record 49 of 83
Author(s): Wetzel, B; Haupert, F; Friedrich, K; Zhang, MQ; Rong, MZ
Title: Impact and wear resistance of polymer nanocomposites at low filler content
Source: POLYMER ENGINEERING AND SCIENCE, 42 (9): 1919-1927 SEP 2002
Abstract: It is well known that inorganic filler particles enhance the mechanical and tribological properties of polymers. The stiffness, toughness, and wear performance of the composites are extensively determined by the size, shape, volume content, and especially the dispersion homogeneity of the particles. In the present study, various amounts of micro- and nano-scale particles (titanium dioxide TiO2, 200-400 nm, calcium silicate CaSiO3, 4-15 mum) were introduced into an epoxy polymer matrix for its reinforcement. The influence of these particles on the impact strength, dynamic mechanical thermal properties, and block-on-ring wear behavior was investigated. Using only the nano-particles, the results demonstrate the best improvement in stiffness, impact strength, and wear resistance of the epoxy at a nano-particle content of 4 vol% TiO2. Therefore, this nanocomposite was used to act as a matrix for the CaSiO3 micro-particles, in the hope of finding synergistic effects between the micro- and the nano-particles. Results show, in fact, a further improvement of wear resistance and stiffness, whereas the impact strength suffers. Geometrical properties of the particles, the homogeneous dispersion state, energy dissipating fracture mechanisms, and a transition of wear mechanisms mostly contribute to the increase in performance.
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Record 50 of 83
Author(s): Ji, QL; Rong, MZ; Zhang, MQ; Friedrich, K
Title: Graft polymerization of vinyl monomers onto nanosized silicon carbide particles
Source: POLYMERS & POLYMER COMPOSITES, 10 (7): 531-539 2002
Abstract: For the purpose of preparing polymer composites filled with SiC nanoparticles to be used in tribological applications, grafting polymerization onto the particles was carried out as a way of surface modification. It is believed that the interfacial interaction in the composites can be tailored in this way. The SiC surface was pre-treated with a silane coupling agent, followed by radical grafting polymerization of acrylamide and styrene, respectively. Infrared spectroscopy and measurement of dispersiveness in solvent demonstrate that the desired polymer chains have been covalently bonded to the surface of the nanoparticles. In addition, the polymerization conditions were investigated and the controlling factors were established accordingly.
Record 51 of 83
Author(s): Rong, MZ; Zhang, MQ; Liu, Y; Zhang, ZW; Yang, GC; Zeng, HM
Title: Mechanical properties of sisal reinforced composites in response to water absorption
Source: POLYMERS & POLYMER COMPOSITES, 10 (6): 407-426 2002
Abstract: The authors discuss the water absorption behaviour of sisal and its epoxy based composites and the mechanical properties of composites that have been aged in water. In addition, a series of fibre pretreatment techniques, including mercerization, acetylation, cyanoethylation, coupling agent treatment and thermal treatment, which are believed to be able to improve the water resistance of sisal and its composites, have been evaluated. It was found that the water absorption behaviour of sisal composites is controlled mainly by the fibre and the fibre/matrix interfacial characteristics. As a result, appropriate fibre modification to retard water diffusion and enhance interfacial adhesion is necessary if the natural fibre composites are to be used in practical applications.
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Record 52 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Shi, G; Yang, GC
Title: All-plant fiber composites. I: Unidirectional sisal fiber reinforced benzylated wood
Source: POLYMER COMPOSITES, 23 (4): 624-633 AUG 2002
Abstract: Benzylation of sawdust from China fir was carried out to prepare plastics based on natural resources. It was found that thermoplasticity and mechanical properties of the chemically modified wood flour changed with the substitution reaction conditions. By compounding sisal fibers and the plasticized fir sawdust, unidirectional laminates were manufactured in a method similar to conventional thermoplastic composites. Such an all-plant fiber composite material is characterized by easy processing, environmental friendliness, and low cost. Instead of chemical heterogeneity of conventional composites, physical heterogeneity of the current natural fiber composite should be favorable for interfacial interaction. However, the reinforcing sisal fibers were not well impregnated by the matrix because of the relatively high viscosity of the benzylated fir sawdust. Further efforts should be made in this area on the basis of the current preliminary work in order to improve mechanical properties of the composites.
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Record 53 of 83
Author(s): Wu, CL; Zhang, MQ; Rong, MZ; Friedrich, K
Title: Tensile performance improvement of low nanoparticles filled-polypropylene composites
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 62 (10-11): 1327-1340 2002
Abstract: it was found beforehand that low nanoparticles loaded polymer composites with improved mechanical performance can be prepared by conventional compounding technique in which the nanoparticles are pre-grafted by some polymers using irradiation. To examine the applicability of the approach, a tougher polypropylene (PP) was compounded with nano-silica by industrial-scale twin screw extruder and injection molding machine in the present work. The results of tensile tests indicated that the nanoparticles can simultaneously provide PP with stiffening, strengthening and toughening effects at a rather low filler content (typically 0.5% by volume). The presence of grafting polymers on the nanoparticles improves the tailorability of the composites. Due to the viscoelastic nature of the matrix and the grafting polymers, the tensile performance of the composites filled with untreated and treated nanoparticles is highly dependent on loading rate. With increasing the crosshead speed for the tensile tests, the dominant failure mode changed from plastic yielding of the matrix to brittle cleavage. (C) 2002 Elsevier Science Ltd. All rights reserved.
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Record 54 of 83
Author(s): Rong, MZ; Zhang, MQ; Liu, Y; Zhang, ZW; Yang, GC; Zeng, HM
Title: Effect of stitching on in-plane and interlaminar properties of sisal/epoxy laminates
Source: JOURNAL OF COMPOSITE MATERIALS, 36 (12): 1505-1526 2002
Abstract: The factors that influence in-plane mechanical responses and mode I interlaminar fracture toughness of stitched unidirectional sisal/epoxy laminates were studied in this paper. It was found that in-plane strength and stiffness of the laminates were not significantly affected by the stitching threads, while the interlaminar toughness was greatly improved, especially at higher sisal content. Unlike glass fiber reinforced polymer composites, sisal laminates have a rather high tolerance against the damages induced by stitching process. In addition, stitching expanded the fiber bridging zone and determined the R-curve profiles of sisal laminates. Factors including stitching density, diameter and species of stitching thread, continuity of stitching, and modification methods of sisal, were proved to greatly influence the delamination resistance of the laminates.
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Record 55 of 83
Author(s): Wei, C; Tan, ST; Wang, XY; Zhang, MQ; Zeng, HM
Title: Effects of liquid crystalline polyurethane on the structure and properties of epoxy
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 21 (9): 719-722 MAY 1 2002
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Record 56 of 83
Author(s): Zeng, R; Wang, SF; Liang, HC; Rong, NZ; Zhang, MQ; Zeng, HM; Gong, QH
Title: Nanostructured silver/polystyrene and ultrafast third-order composite film: Preparation optical nonlinearity
Source: POLYMERS & POLYMER COMPOSITES, 10 (4): 291-298 2002
Abstract: Surface-modified silver nanoparticles with various sizes, synthesized by water-in-oil micro-emulsion, were incorporated into polystyrene (PS) to form transparent nanocomposite films through solution-mixing and static-casting. It was found that the Ag nanoparticles could be re-dispersed well in the polymer matrix by using chloroform as a solvent due to a strong interaction between Ag and chloroform. XPS analysis suggested that there is no obvious interaction between nanosilver and the polystyrene matrix. The third-order nonlinear optical susceptibility of Ag/PS nanocomposite films is around (10).esu and increases with increasing particle size, as measured by the time-resolved femtosecond optical Kerr effect experiment at a wavelength of 830nm. The results demonstrate that the present fabrication approach can effectively tailor the structure and properties of the nanocomposites.
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Record 57 of 83
Author(s): Rong, MZ; Zhang, MQ; Liu, Y; Yan, HM; Yang, CG; Zeng, HM
Title: Interfacial interaction in sisal/epoxy composites and its influence on impact performance
Source: POLYMER COMPOSITES, 23 (2): 182-192 APR 2002
Abstract: To obtain comprehensive knowledge of the interfacial effect on the impact performance of sisal fiber reinforced epoxy composites, the fiber surface was modified in different ways prior to compounding. By using a surface tensiometer and dynamic mechanical analyzer, interfacial interactions in the composites were characterized. The results indicated that the chemical treatments brought about strong bonding between sisal bundles and the epoxy matrix. The subsequent impact tests revealed that the microfailure mechanism involved is a function of interfacial adhesion and fiber length continuity (i.e., continuous or discontinuous fiber). In the case of unidirectional laminates, an optimum fiber treatment should be able to result in an increased affinity between fiber bundles and matrix and a decreased intercellular adhesion. In this way, extension and uncoiling of the spirally arranged microfibrils, a main energy consumption process of plant fibers, can impart significant toughness to the composites. For short fiber composites, the interfacial strength should be properly tailored so as to increase energy dissipation through debonding and pull-out of fiber bundles.
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Record 58 of 83
Author(s): Zeng, R; Rong, MZ; Zhang, MQ; Liang, HC; Zeng, HM
Title: Laser ablation of polymer-based silver nanocomposites
Source: APPLIED SURFACE SCIENCE, 187 (3-4): 239-247 FEB 28 2002
Abstract: Polymer films (polystyrene and acrylonitrile-styrene copolymer) filled with silver nanoparticles were analyzed by optical absorption spectrometry, X-ray photoelcctron spectrometry and laser ablation/time-of-flight mass spectrometry. The results indicated that optical absorption of polymer films was affected by Ag nanoparticles; and the interfacial interactions between Ag and the polymer matrices, and the latter was highly dependent on the chemical structure of the polymers. The mass spectral data further demonstrated that the incorporation of Ag nanoparticles into polymers significantly changed the laser ablation mechanism and the products of the polymers. As a result, nano-Ag/polymer films showed a Ag-induced laser-decomposition behavior accompanied by a series of carbon cluster negative ions. (C) 2002 Elsevier Science B.V. All rights reserved.
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Record 59 of 83
Author(s): Zhang, MQ; Rong, MZ; Yu, SL; Wetzel, B; Friedrich, K
Title: Improvement of tribological performance of epoxy by the addition of irradiation grafted nano-inorganic particles
Source: MACROMOLECULAR MATERIALS AND ENGINEERING, 287 (2): 111-115 FEB 18 2002
Abstract: Communication: To develop wear resistant nanocomposite coating materials, the authors of the present work treated nanosilica first by introducing a certain amount of grafting polymers onto the particles in terms of an irradiation technique. Through irradiation grafting, the nanoparticle agglomerates turn into a nanocomposite microstructure. (comprised of the nanoparticles and the grafted, homopolymerized secondary polymer), which in turn built up a strong interfacial interaction with the surrounding epoxy matrix through chain entanglement and chemical bonding during the subsequent mixing and consolidation. The experimental results indicated that the addition of the grafted nanosilica into epoxy significantly reduced wear rate and frictional coefficient of the matrix at low filter loading. Compared with the cases of microsized silica and untreated nanosilica, the employment of grafted nanosilica provided composites with much higher tribological performance enhancement efficiency. Unlike the approaches for manufacturing of other types of nanocomposites, the current method is characterized by many advantages, such as simple, low cost, easy to be controlled, and broader applicability.
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Record 60 of 83
Author(s): Shumsky, VF; Privalko, EG; Karaman, VM; Privalko, VP; Walter, R; Friedrich, K; Zhang, MQ; Rong, MZ
Title: Viscoelastic behaviour of polypropylene-based nanocomposites in the melt state
Source: ADVANCED COMPOSITES LETTERS, 10 (4): 191-195 2001
Abstract: Nanoparticles of the standard pyrogenic Aerosil 1380 (Degussa) pregrafted by gamma -irradiation with styrene were melt-compounded with the general purpose isotactic polypropylene (PP) homopolymer by a single-screw extruder. Storage G'(omega) and loss G "(omega) shear moduli of the neat PP (PP-0) and of the nanocomposite with the filler volume content 4.68% (PP-4.68) were treated to derive the relaxation times spectra h (tau) using the NLREG computer program based on Tikhonov's method of non-linear regularisation. Drastic changes in the pattern, and broadening of the h (tau) to longer relaxation times for the PP-4.68 were attributed to the onset of plastic yield of a spatial network of filler particles coated with polymer boundary layer, preceding the macroscopic melt flow.
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Record 61 of 83
Author(s): Li, TQ; Zhang, MQ; Zeng, HM
Title: Processing dependent morphology, interfacial interaction and shear behavior of short carbon fiber reinforced PEEK
Source: COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, 32 (12): 1727-1733 2001
Abstract: Shear properties of compression-molded discontinuous AS4 carbon fiber reinforced poly(ether ether ketone) composites are evaluated with Iosipescu tests. It is found that both shear modulus and shear strength strongly depend on the molding conditions. A comparison between shear behavior of the composites and composites morphology reveals that fusion of the composite pellets and fiber/matrix interfacial interaction on molecular scale are the two dominant factors which determine the processing dependent shear properties of the materials studied. (C) 2001 Elsevier Science Ltd. All rights reserved.
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Record 62 of 83
Author(s): Zeng, R; Rong, MZ; Zhang, MQ; Liang, HC; Zeng, HM
Title: Interfacial interaction in Ag/polymer nanocomposite films
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 20 (16): 1473-1476 2001
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Record 63 of 83
Author(s): Rong, MZ; Zhang, MQ; Liu, Y; Yang, GC; Zeng, HM
Title: The effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 61 (10): 1437-1447 2001
Abstract: The present paper investigates the effect of fiber treatment on the mechanical properties of unidirectional sisal-reinforced epoxy composites. Treatments including alkalization. acetylation, cyanoethylation, the use of silane coupling agent. and heating were carried out to modify the fiber surface and its internal structure. As indicated by infrared spectroscopy. X-ray diffraction and tensile tests, variations in composition. structure. dimensions. morphology and mechanical properties of the sisal fibers can be induced by means of different modification methods. When the treated fibers were incorporated into an epoxy matrix, mechanical characterization of the laminates revealed the importance of two types of interface: one between fiber bundles and the matrix and the other between the ultimate cells. In general, fiber treatments can significantly improve adhesion at the former interface and also lead to ingress of the matrix resin into the fibers, obstructing pull-out of the cells. As a result, the dependence of laminate mechanical properties on treatment methods becomes complicated. On the basis of a detailed analysis, the relationship between optimized fiber treatment and performance improvement of sisal composites was proposed. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.
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Record 64 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Shi, G; Yang, GC
Title: All-plant fibre composites: Self reinforced composites based on sisal
Source: ADVANCED COMPOSITES LETTERS, 10 (2): 73-79 2001
Abstract: In the present work slight benzylation of sisal fibre was carried out to prepare natural resource based self reinforced composites. By controlling the degree of benzylation, the outer layer of the ultimate cells was converted into thermoplastic and the inner part maintained the load bearing ability. When these modified fibres were moulded under certain temperature and pressure, the thermoplasticised portion flowed freely and served as matrix, while the unaffected parts in the core can still provide reinforcing effect. Such an all-plant fibre composite is characterised by self-reinforcement, easy processing and low cost.
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Record 65 of 83
Author(s): Tan, ST; Zhang, MQ; Rong, MZ; Zeng, HM; Zhao, FM
Title: Properties of metal fibre filled thermoplastics as candidates for electromagnetic interference shielding
Source: POLYMERS & POLYMER COMPOSITES, 9 (4): 257-262 2001
Abstract: Polypropylene (PP) based conductive composites were produced using stainless steel fibres (SSF) as the fillers. Their mechanical properties. electrical conductivity and electromagnetic interference (EMI) shielding effectiveness were measured. For the purposes of performance optimization, polypropylene grafted maleic anhydride copolymer (PP-g-MAH) was added. The results indicate that when PP was replaced by PP-g-MAH, the mechanical properties of the composites can be improved, but the conductivity decreased remarkably. However, a positive synergistic effect was found in the case of SSF/PP-g-MAH/PP, which was characterized by acceptable strength and modulus as well as by an EMI attenuation ability of 30dB.
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Record 66 of 83
Author(s): Taipalus, R; Harmia, T; Zhang, MQ; Friedrich, K
Title: The electrical conductivity of carbon-fibre-reinforced polypropylene/polyaniline complex-blends: experimental characterisation and modelling
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 61 (6): 801-814 2001
Abstract: The aim of this study is to characterise and model the electrical conductivity of carbon-fibre-reinforced polypropylene/polyaniline-complex blends. A correlation between the electrical conductivity and the microstructure of both the blends and the composites was found; the fibre concentration, orientation and average length affected the electrical conductivity. In addition, a synergy effect between PANI-complex and carbon fibres in the polypropylene matrix regarding the electrical conductivity occurred. In particular, the percolation threshold of carbon-fibre composites was moved towards a reduced fibre content when the blend consisted of both PANI-complex and carbon fibre. A fibre-contact model was used to describe the electrical conductivity of carbon-fibre-composites and PANI-complex-blends. It was expanded to predict also the synergy effect between LCF and PANT-complex. The predictions were in good agreement with the experimental data. (C) 2001 Elsevier Science Ltd. All rights reserved.
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Record 67 of 83
Author(s): Rong, MZ; Zhang, MQ; Liu, H; Zeng, HM
Title: Microstructure and tribological behavior of polymeric nanocomposites
Source: INDUSTRIAL LUBRICATION AND TRIBOLOGY, 53 (2): 72-77 MAR-APR 2001
Abstract: Nanocomposites represent a new prospective branch in the huge field of polymer materials science and technology. It has been shown that an overall enhancement of properties of polymers can be achieved under certain conditions by the addition of nanoparticles. To examine the influence of microstructure on the tribological performance of nanocomposites, different ways of compounding were used in this study. It was found that the friction and wear behavior of polymeric nanocomposites under sliding environment was rather sensitive to the dispersion states of the nanoparticles. When the microstructural homogeneity of the nanocomposites was improved, their wear resistance could be increased significantly. The present work demonstrates the importance of TiO2-nanoparticles dispersion in an epoxy resin matrix, on the materials' tribological properties, when sliding against a smooth steel counterpart.
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Record 68 of 83
Author(s): Li, TQ; Zhang, MQ; Zeng, HM
Title: Interfacial interaction of carbon fiber/PEEK and its effect on the mechanical performance
Source: PROGRESS IN NATURAL SCIENCE, 11 (4): 241-249 APR 2001
Abstract: An in-depth survey of the researches is presented on the anisotropic structure and properties of interphase in carbon fiber reinforced polyetheretherketone composites. The formation and structural nature of interfacial short-range and long-range effects, micromechanical and macromechanical roles of interphase are discussed. Besides, prospects of further studies and a novel methodology for revealing interfacial properties of thermoplastic composites are demonstrated.
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Record 69 of 83
Author(s): Rong, MZ; Zhang, MQ; Zheng, YX; Zeng, HM; Walter, R; Friedrich, K
Title: Irradiation graft polymerization on nano-inorganic particles: An effective means to design polymer-based nanocomposites
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 19 (13): 1159-1161 JUL 2000
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Record 70 of 83
Author(s): Li, TQ; Zhang, MQ; Zeng, HM
Title: Structure aspects of interfacial stress transfer in a fiber/thermoplastic composite
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 19 (10): 837-839 MAY 2000
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Record 71 of 83
Author(s): Li, TQ; Zhang, MQ; Zhang, K; Zeng, HM
Title: The dependence of the fracture toughness of thermoplastic composite laminates on interfacial interaction
Source: COMPOSITES SCIENCE AND TECHNOLOGY, 60 (3): 465-476 2000
Abstract: The paper investigates the influence of microstructure of the matrix resin and polymer/reinforcement interface on the fracture performance of thermoplastic composites in relation to processing conditions. Solution-pre-impregnated, unidirectional, carbon-fiber-reinforced poly(ether ether ketone) laminates prepared at different melt residual times were used as the experimental materials to obtain different interfacial effects and matrix morphologies. Composite crystalline structures were analyzed by X-ray diffraction and infrared spectroscopy. The stress-intensity factor was measured by means of the single-edge-notched bending method along the two orthogonal directions of the laminates. The results indicate that the Mode-I fracture toughness along the fiber direction, K-IC", increases with a rise in melt residual time, while the stress-intensity factor at failure perpendicular to the fiber direction, K-IC(perpendicular to), changes with the melt residual time in a more complicated way. Through a careful comparison of the two stress-intensity factors with composite microstructure, the dependence of the fracture toughness on the crystalline morphology of the matrix resin has been found. That is, K-IC(perpendicular to) increases with increasing matrix crystallinity and K-IC" increases with either a decrease in the heterogeneous crystallization or an increase in the orientation of matrix crystallites. It is, thus, proved that the fracture toughness of the laminates depends on crystallinity and crystalline morphology of the matrix as well as the interfacial interaction, but not merely on matrix crystallinity. (C) 2000 Elsevier Science Ltd. All rights reserved.
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Record 72 of 83
Author(s): Lu, X; Zhang, MQ; Rong, MZ; Shi, G; Yang, GC; Zeng, HM
Title: Natural vegetable fibre/plasticised natural vegetable fibre - A candidate for low cost and fully biodegradable composite
Source: ADVANCED COMPOSITES LETTERS, 8 (5): 231-236 1999
Abstract: A novel fibre composite consisting of natural vegetable fibre as the reinforcer and plasticised natural vegetable fibre as the matrix was studied. By means of cyanoethylation and chlorination, pine sawdust and chopped sisal were converted into thermoplastics and then compounded with sisal and ramie fibres. The natural fibre composite not only exhibits properties similar to those of conventional fibre composites, but also is characterised by easy processing, enviromental frendliness, low cost and capability of tailoring property due to the physically heterogeneous nature.
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Record 73 of 83
Author(s): Li, TQ; Zhang, MQ; Zeng, HM
Title: A preliminary proof of the quasi-epitaxial growth of a semicrystalline polymer in its short carbon fiber composites
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 18 (22): 1861-1864 NOV 1999
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Record 74 of 83
Author(s): Yu, G; Zhang, MQ; Zeng, HM
Title: Interfacial phenomena in polymer based PTC material
Source: COMPOSITE INTERFACES, 6 (4): 275-285 1999
Abstract: Polymer based PTC (positive temperature coefficient) composites are of special interest since they have great potential in temperature sensitive devices. In order to obtain a reproducible PTC composite with acceptable PTC intensity, the effects of processing conditions and filler treatment with nitric acid and titanate coupling agents on room temperature resistivity, PTC intensity, and melt viscosity of carbon black filled low density polyethylene composites have been described and discussed in the present paper. The results show that interfacial effect is a key factor influencing the processability and ultimate material performance, which can be tailored in various ways.
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Record 75 of 83
Author(s): Tan, ST; Zhang, MQ; Rong, MZ; Zeng, HM
Title: Effect of interfacial modification on metal fiber filled polypropylene composites and property balance
Source: POLYMER COMPOSITES, 20 (3): 406-412 JUN 1999
Abstract: Mechanical properties and electrical conductivity of discontinuous stainless steel fiber (SSF) filled polypropylene (PP) composites were considered as candidates for shielding electromagnetic interference (EMI) applications. In order to improve the unsatisfied impact resistance, surface treatments of SSF and modified PP were introduced. By means of a microdroplet pull-out test, polypropylene grafted maleic anhydride copolymer (PP-g-MAH) was found to be able to enhance the poor interfacial adhesion between fiber and matrix. On this basis, PP-g-MAH was used to prepare conventional composites, and the macromechanical measurements showed evidence that PP-g-MAH helped increase both flexural and impact strength of the composites. However, the good affinity of PP-g-MAH for SSF reduced composite conductivity accordingly. Finally, blends of PP and PP-g-MAH proved to be a solution for the problem, i.e., the impact strength was increased significantly while acceptable electrical resistivity was maintained.
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Record 76 of 83
Author(s): Yu, G; Zhang, MQ; Zeng, HM
Title: Carbon black filled polyolefine as a PTC material: Melt rheological behavior
Source: ADVANCED COMPOSITES LETTERS, 6 (6): 161-166 1997
Abstract: The melt rheological properties of low density polyethylene filled with carbon black as a PTC material have been investigated, in the shear rate range 11.52 to 2280 s(-1). The data obtained in a capillary rheometer were presented to describe the effect of content, morphology and treatments of carbon black as well as shear rate on flow behavior, melt viscosity, temperature sensitivity and shear sensitivity, in hopes of giving preliminary references far a better understanding of the relationship between composition, processing and property of this kind of material.
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Record 77 of 83
Author(s): Zhang, MQ; Song, L; Zeng, HM
Title: Wear status estimation of fiber composite through fractal characterization of wear debris
Source: ADVANCED COMPOSITES LETTERS, 5 (5): 137-141 1996
Abstract: As the product of mass loss during friction and wear, wear debris carries extensive information about the tribological process. By using fractal geometry, the authors of the present paper quantitatively characterize the morphologies of the wear particles of short carbon fiber reinforced polyetheretherketone (PEEK). The experimental results show that the fractal dimensions of the wear particles are closely correlated to the wear status of the bulk composites. Basing upon this investigation, one can predict or estimate wear conditions of tribological components made of polymer composites in practice.
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Record 78 of 83
Author(s): Zhang, MQ; Friedrich, K; Batzar, K; Thomas, P
Title: Abrasive wear mechanisms of fluoropolymer based composite coatings on aluminum substrates
Source: WEAR, 200 (1-2): 122-136 DEC 1 1996
Abstract: Experimental studies on wear performance and wear mechanisms of Fluoropolymer based composite, non-stick coatings on aluminum substrates were carried out by using particular wear testing methods, i.e. the ''mechanical tiger paw (MTP) Test'' and the ''Nord Test''. Both are supposed to simulate household abrasive operating conditions in a laboratory environment. It was Found that the wear process involved in the MTP Test was an accelerated one, but that in the Nord Test was decelerated due to a transition from severe three-body abrasion to milder two-body sliding wear. In addition, both effects of the microstructure of the coatings and of the surface treatment of the substrates were discussed.
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Record 79 of 83
Author(s): Zhang, MQ; Lu, ZP; Friedrich, K
Title: On the wear debris of polyetheretherketone: Fractal dimensions in relation to wear mechanisms
Source: TRIBOLOGY INTERNATIONAL, 30 (2): 87-102 FEB 1997
Abstract: It has been recognized that wear debris contains extensive information about wear and friction of materials. Investigation of wear debris is important for tribological research. In order to find out an effective way that is able to diagnose and predict the wear state of polymers, the authors investigated the relationship between the wear debris morphology and the wear behaviour of the bulk material. Polyetheretherketone (PEEK) was employed as the model material. Its sliding wear and friction properties were measured by means of a pin-on-disc apparatus. At a constant sliding velocity of 1 m s(-1), the specific wear rate was independent of load under lower loading conditions (1-4 MPa) but increased with a rise in load under higher loading conditions (4-8 MPa). The coefficient of friction was insensitive to the variation of contact pressure. The possible mechanisms involved were analysed on the basis of the wear debris morphology as well as the wear performance. Fractal geometry, which describes non-Euclidean objects, was applied to the quantitative analysis of the boundary texture of the wear debris due to the fact that the qualitative assessment of the wear debris morphology was not effective enough to reflect the geometrical variation of the fragmental shapes. The experimental results demonstrated that the wear debris were fractals, and could be characterized with the fractal dimensions which were determined by the slit island method. In addition, it was found that the fractal dimension of the wear debris was closely related to the wear behaviour of PEEK, and can be regarded as a measure of wear rate. Copyright (C) 1996 Elsevier Science Ltd
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Record 80 of 83
Author(s): Zhang, MQ; Lu, ZP; Friedrich, K
Title: Thermal analysis of the wear debris of polyetheretherketone
Source: TRIBOLOGY INTERNATIONAL, 30 (2): 103-111 FEB 1997
Abstract: Differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) were used to study the thermal performance of the wear debris and the worn pin tops of polyetheretherketone (PEEK) after unlubricated sliding wear tests at a constant sliding speed of 1 m s(-1). It was found that the friction interfacial temperature might have ranged from 300 degrees C to 345 degrees C, hence favouring plastic flow mechanisms to occur and resulting in lubricating effects. In addition, thermal oxidative cross-linking reactions took place in PEEK as the wear testing proceeded, causing a reduction in the crystallizability. The most significant changes in thermal behaviour were observed from the wear debris produced under lower loadings (i.e. 1 and 3 MPa). The possible structure-property relationships that might have affected the wear mode and the morphological feature of the wear debris are discussed. Copyright (C) 1996 Elsevier Science Ltd
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Record 81 of 83
Author(s): Zhang, MQ; Song, LE; Zeng, HM; Friedrich, K
Title: Predictability of wear status provided by fractal dimensions of wear particles
Source: JOURNAL OF MATERIALS SCIENCE LETTERS, 15 (15): 1288-1290 AUG 1 1996
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Record 82 of 83
Author(s): Zhang, MQ; Friedrich, K; Batzar, K; Thomas, P
Title: Wear transition in fluoropolymer based composite coatings
Source: ADVANCED COMPOSITES LETTERS, 5 (2): 43-48 1996
Abstract: Abrasive wear behavior of fluoropolymer based composite coatings was investigated by using a particular wear testing method, the Nord Test. It was found that the abrasion process was a decelerated one due to a transition from three-body abrasion to two-body sliding wear. Coating thickness but not material microstructure controlled the wear performance of the present coating systems.
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Record 83 of 83
Author(s): ZHANG, MQ; XU, JR; ZENG, HM; HUO, Q; ZHANG, ZY; YUN, FC; FRIEDRICH, K
Title: FRACTAL APPROACH TO THE CRITICAL FILLER VOLUME FRACTION OF AN ELECTRICALLY CONDUCTIVE POLYMER COMPOSITE
Source: JOURNAL OF MATERIALS SCIENCE, 30 (17): 4226-4232 SEP 1 1995
Abstract: It has been known for quite a long time that polymers filled with electrically conductive particles, foils or fibres exhibit a distinctive dependence of conductivity on filler volume fraction. With a rise in filler content, there is always a drastic increase in composite conductivity by the order of ten magnitudes at a certain threshold, namely, the critical volume fraction. Such a transition-like change in conductivity is usually interpreted as percolation. Many models have been proposed for explaining the conduction mechanism involved, but often they possess evident drawbacks mainly due to the negligence of relative filler arrangements or the Euclidean geometric description of the arrays. The present work focused on the prediction of the critical volume fraction by a new electrical conductive model, based on the fractal technique and the generalized unit-cell method proposed by Pitchumani and Yao for modelling the thermal conductivity of fibrous composites. It was found that the electrical conduction behaviour of a polymer composite is governed by both a filler geometry factor and a material factor of the components. The critical volume fractions estimated by the model are in good agreement with experimental results taken from the literature. In addition, possible improvements of the present approach are discussed.
