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Composites Decreased (composite + decreased)
Selected AbstractsTribological Behavior of SiC-Reinforced Ti3SiC2 -Based Composites under Dry Condition and under Lubricated Condition with Water and EthanolJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2006Yuko Hibi To evaluate the lubrication compatibility of SiC-reinforced Ti3SiC2 -based composites, i.e., a Ti3SiC2/SiC composite, with water and alcohol, sliding experiments were conducted under dry condition and lubricated with water and C2H5OH. The friction and wear of the Ti3SiC2/SiC composite decreased in the order of dry condition, in water, and in C2H5OH. The worn surfaces indicated that oxide masses, which caused oxidation wear and abrasive wear, were formed by tribo-oxidation on the sliding surface under the dry condition and in water, while tribo-oxidation scarcely occurred in C2H5OH. [source] The effect of lanthanum oxide (La2O3) on the structure and crystallization of poly(vinylidene fluoride)POLYMER INTERNATIONAL, Issue 7 2010Jianbin Song Abstract Rare earth polymers, due to their excellent luminescence, fluorescence, laser protective, optical and magnetic properties, have attracted much research attention in recent years. However, little attention has been paid to the effect of rare earths on the structure and crystallization of polymers, which is of important significance in the development of functional polymers. X-ray diffraction and differential scanning calorimetry were used to investigate the structure and crystallization behavior of a poly(vinylidene fluoride) (PVDF)/lanthanum oxide (La2O3) composite. The results showed that the degree of perfection, crystal size, crystallization rate and isothermal crystallization activation energy of PVDF in the composite decreased, compared with pure PVDF. The spherulite nucleation and growth for PVDF and PVDF composite were analyzed in detail using the Lauritzen-Hoffman equation. The modified Avrami equation and the Mo equation were used to study the non-isothermal crystallization kinetics. The addition of La2O3 did not change the crystal structure and nucleation process for PVDF, but it decreased markedly the crystal growth rate and led to the formation of unstable crystals. This was attributed to the fact that too much La2O3 prevented PVDF molecular chains from moving and arranging in an orderly manner into crystals. Copyright © 2010 Society of Chemical Industry [source] Preparation and properties of ternary polyimide/SiO2/polydiphenylsiloxane composite filmsPOLYMER INTERNATIONAL, Issue 11 2006Zhenping Shang Abstract A series of novel ternary polyimide/SiO2/polydiphenylsiloxane (PI/SiO2/PDPhS) composite films were prepared through co-hydrolysis and condensation between tetramethoxysilane, diphenyldimethoxysilane (DDS) and aminopropyltriethoxysilane-terminated polyamic acid, using an in situ sol,gel method. The composite films exhibited good optical transparency up to 30 wt% of total content of DDS and SiO2. SEM analysis showed that the PDPhS and SiO2 were well dispersed in the PI matrix without macroscopic separation of the composite films. TGA analysis indicated that the introduction of SiO2 could improve the thermal stability of the composite films. Dynamic mechanical thermal analysis showed that the composite films with low DDS content (5 wt%) had a higher glass transition temperature (Tg) than pure PI matrix. When the content of DDS was above 10 wt%, the Tg of the composite decreased slightly due to the plasticizing effect of flexible PDPhS linkages on the rigid PI chains. The composite films with high SiO2 content exhibited higher values of storage modulus. Tensile measurements also showed that the modulus and tensile strength of the composite films increased with increasing SiO2 content, and the composite films still retained a high elongation at break due the introduction of DDS. The density and water absorption of the composite films were also characterized. Copyright © 2006 Society of Chemical Industry [source] Effects of curing systems and polysulfonamide pulp on the curing characteristics, mechanical properties, and swelling behavior of ethylene,propylene,diene elastomer compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Xiaolong Jia Abstract The effects of three curing systems and polysulfonamide (PSA) pulp on the curing characteristics, mechanical properties, and swelling behavior of ethylene,propylene,diene elastomer (EPDM) composites were investigated. The maximum torque value and the optimum curing time were highest for EPDM composites cured with a peroxide system, and they were closely followed by those cured with a sulfur system. In comparison with those cured with peroxide and phenolic resin systems, EPDM composites cured with the sulfur system showed higher mechanical properties and dimensional stability. With increasing PSA pulp content, the maximum torque value of the EPDM composites increased, whereas the optimum curing time of the composites decreased. The orientation percentage of the PSA pulp in the EPDM composites was maximum at 30 phr pulp, as determined from green strength measurements. In the longitudinal direction along which the pulp was oriented, the EPDM composites showed higher tensile strength as well as lower elongation and swelling ratios. Also, with increasing PSA pulp content, the tensile strength of the EPDM composites decreased up to 10 phr pulp and subsequently increased, whereas the elongation and swelling ratio of the EPDM composites decreased linearly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Epoxy composites reinforced by different size silica nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Cheng-Fang Ou Abstract Three series of epoxy/SiO2 composites, containing 0.3,7 wt % nanosized SiO2 with different specific surface area, were prepared by solution blending. The resulting composites exhibit the higher glass transition temperature (Tg) than that of pure epoxy. The Tg of composite showed a maximum increment of 35.3°C by the addition of 7 wt % A300. The trade name of A300 is Aerosil 300. It is one of the fumed silica nanoparticles products of Degussa. The decomposition temperatures (Td) of composites were always higher than that of pure epoxy and showed a maximum increment of 20.8°C by the addition of 5 wt % A300. The light transmittance of composites was as a function of the SiO2 content and size. The water permeability of composites decreased with increasing SiO2 content and the 7 wt % A300 composite exhibits a maximum decrement percentage of 35.6%. The Tg, Td, storage modulus, and water-vapor barrier property are as a function of the SiO2 content and size. These properties increased as the content of SiO2 increased. The finer SiO2 are more effective in increasing the Tg, Td, and water-vapor barrier property. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Tribological Properties of Polycrystalline Ti3SiC2 and Al2O3 -Reinforced Ti3SiC2 CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Chunfeng Hu Tribological properties of Ti3SiC2 and Al2O3 -reinforced Ti3SiC2 composites (10 and 20 vol% Al2O3) were investigated by using an AISI-52100 bearing steel ball dryly sliding on a linear reciprocating athletic specimen. The friction coefficients were found varying only in a range of 0.1 under the applied loads (2.5, 5, and 10 N), and the wear rates of the composites decreased with increasing Al2O3 content. The enhanced wear resistance is mainly attributed to the hard Al2O3 particles nail the surrounding soft matrix and decentrale the shear stresses under the sliding ball to reduce the wear losses. [source] Effect of Interfacial Reaction on the Thermal Conductivity of Al,SiC Composites with SiC DispersionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Chihiro Kawai The effect of interfacial reactions between Al and SiC on the thermal conductivity of SiC-particle-dispersed Al-matrix composites was investigated by X-ray diffraction and transmission electron microscopy (TEM), and the thermal barrier conductance (hc) of the interface in the Al,SiC composites was quantified using a rule of mixture regarding thermal conductivity. Al,SiC composites with a composition of Al (pure Al or Al,11 vol% Si alloy),66.3 vol% SiC and a variety of SiC particle sizes were used as specimens. The addition of Si to an Al matrix increased the thermal barrier conductance although it decreased overall thermal conductivity. X-ray diffraction showed the formation of Al4C3 and Si as byproducts in addition to Al and SiC in some specimens. TEM observation indicated that whiskerlike products, possibly Al4C3, were formed at the interface between the SiC particles and the Al matrix. The thermal barrier conductance and the thermal conductivity of the Al,SiC composites decreased with increasing Al4C3 content. The role of Si addition to an Al matrix was concluded to be restraining an excessive progress of the interfacial reaction between Al and SiC. [source] Effects of stearic acid on the interface and performance of polypropylene/superfine down powder compositesPOLYMER COMPOSITES, Issue 12 2009Xin Liu To manufacture the hygroscopic sheets available for functional application, superfine down powder (SDP) and stearic acid modified superfine down powder (MSDP) were, respectively, blended and extruded with polypropylene (PP) to produce composite pellets, and the extruded pellets were hot-pressed into composite sheets. The chemical reaction between SDP and stearic acid was characterized using the attenuated total reflection attachment on the Fourier transform infrared. PP/MSDP composites showed more uniform powder dispersion in PP matrix, higher compatibility, and better mechanical properties than that of PP/SDP composites, which showed an evident decrease in tensile strength and elongation at break compared with pure PP. It was worth noting that the Young's modulus of PP/SDP composites was higher than that of pure PP, but lower than that of PP/MSDP composites. The addition of SDP led to a large increase in water absorption of PP/SDP composites. However, the water absorption of PP/MSDP composites decreased slightly compared with that of PP/SDP composites. Furthermore, the effects of SDP and MSDP on the microstructural and thermal properties of different composites were also investigated, respectively. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Polyethylene-Palygorskite nanocomposite prepared via in situ coordinated polymerizationPOLYMER COMPOSITES, Issue 4 2002Junfeng Rong A polyethylene/palygorskite nano-composite (IPC composite) was prepared via an in-situ coordinated polymerization method, using TiCl4 supported on palygorskite fibers as catalyst and alkyl aluminum as co-catalyst. These composites were compared with those prepared by melt blending (MBC composites). It was found that in the IPC composites, nano-size fibers of palygorskite were uniformly dispersed in the polyethylene matrix. In contrast, in the MBC composites, the palygorskite was dispersed as large clusters of fibers. Regarding the mechanical properties of the IPCs, the tensile modulus increased and the elongation at break decreased with increasing fiber content, while the tensile strength passed through a maximum. The tensile strength and elongation at break were much smaller for the MBC composites. The final degree of crystallinity of the IPC composites decreased with increasing palygorskite content. Regarding the kinetics of crystallization, the ratio between the degree of crystallinity at a given time and the final one was a universal function of time. It was found that large amouns of gel were present in the IPC composites and much smaller amountes in the MBC composites. [source] | ||||||||||