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131.
Youyi Sun Yaqing Liu Guizhe zhao Xing Zhou Qijin Zhang Yan Deng 《Materials Chemistry and Physics》2008,111(2-3):301-304
The functional group of sulfur was introduced into the PMMA terminus by the reversible addition-fragmentation transfer (RAFT) technique and the PMMA/Ag nanocomposite film was prepared by the in situ synthetic method. The third-order nonlinear optical properties of the material were further investigated by the Z-scan technique. The result shows that the χ(3) nonlinearity of the material depend on the doped content of Ag nanoparticles and is obtained to be 6.22 × 10−9 esu at the content of 2.4 wt%. Furthermore, it is found that the material has the potential application on optical switcher at the content of 0.8 wt%. 相似文献
132.
The evolutions of ratcheting strains of polymethyl methacrylate (PMMA) at different temperatures and stress levels were experimentally investigated. A steady ratcheting strain growth region with a constant rate was observed in all specimens, which occupied significant part of total fatigue failure life. Experimental results also showed that the steady ratcheting growth rate varied with applied temperatures and loading. In this paper, theory of thermally activated process for glassy polymers was used to describe the plastic deformations during the cycle. Based on the correlations between ratcheting strains per cycle and hysteresis loop energy, a new ratcheting strains accumulative model for polymer materials was developed, which quantificationally elucidated the effects of temperature, loading frequency, mean stress and stress amplitude on the accumulative rate of ratcheting strains. Comparing the predications from the proposed model with experimental ratcheting strain data of PMMA, it was found that the model could describe the steady ratcheting strain accumulative behaviors under arbitrary temperatures and loading conditions exactly. 相似文献
133.
Poomali Siddaramaiah B. Suresha Joong-Hee Lee 《Materials Science and Engineering: A》2008,492(1-2):486-490
The blends of poly(methyl methacrlate) (PMMA) and thermoplastic polyurethane (TPU) were prepared by a Brabender co-twin screw extruder. The mechanical and three-body abrasive wear behaviour of PMMA/TPU blends has been studied. Three-body abrasive wear tests were conducted using rubber wheel abrasion tester (RWAT) under different abrading distances at 200 rpm and 22 N load. A significant reduction in tensile strength and tensile modulus with an increase in TPU content in the blend formulation was observed. Three-body abrasive wear results indicate that the wear volume increases with increase in abrading distance for all the samples studied. However, neat PMMA showed better wear resistance as compared to PMMA/TPU blends. The worn surface features, as examined through scanning electron microscope (SEM), show matrix cracking and deep furrows in PMMA/TPU blends. 相似文献
134.
PMMA/SiO2杂化纤维的制备及表征 总被引:1,自引:0,他引:1
以正硅酸乙酯(TEOS)和PMMA低聚体为原料,乙烯基三乙氧基硅烷(VTEOS)为偶联剂,采用溶胶-凝胶法制备了PMMA/SiO2杂化溶胶,陈化后用提拉法制得PMMA/SiO2杂化纤维。研究了溶胶的杂化反应机理、成纤性能;使用IR、SEM、TGA及DSC分析了杂化纤维的结构与性能。结果表明,该杂化溶胶具有很好的拉丝性能,黏度为180 Pa.s~300 Pa.s时的成纤性能好,所制得的杂化纤维,其中PMMA与SiO2之间通过化学键连接,在纤维内部有机无机相间形成均一的连续相;其耐热性能优于纯PMMA。 相似文献
135.
分别用磁控溅射和等离子体增强化学气相沉积方法在PMMA基底上沉积硅膜和含氢非晶碳(a-C:H)膜.用氩离子溅射硅靶制备硅膜,以甲烷和氢气为反应气体在不同自偏压下制备非晶碳膜.分别用原子力显微镜、X射线光电子能谱和紫外拉曼光谱表征薄膜的形貌和结构,并分别用纳米压痕仪和栓盘摩擦磨损试验机测试其机械和摩擦学性能.结果表明,沉积碳膜的PMMA基底呈现出高硬度、低摩擦系数和低磨损率的特性.碳膜的显微结构、机械和摩擦学特性均显著依赖薄膜沉积过程中使用的自偏压,其摩擦系数和磨损率与其硬度和sp3含量密切相关. 相似文献
136.
138.
利用两步酸、碱催化溶胶-凝胶法及原位聚合法制备PMMA/SiO2(聚甲基丙烯酸甲酯SiO2)杂化凝胶,并对该材料进行红外分析,研究不同工艺条件下PM-MA/SiO2杂化凝胶结构及性能。 相似文献
139.
Claudia I Vallo 《Polymer International》2000,49(8):831-838
Acrylic bone cements are widely used in orthopaedics, and it is generally accepted that due to the vitrification phenomenon the monomer does not reach complete conversion after the cure of the resin. The degree of polymerization attainable in a commercial acrylic bone cement based on poly(methylmethacrylate) (PMMA) has been investigated by differential scanning calorimetry (DSC) using isothermal and dynamic modes. Because DSC tends to be less sensitive at high conversions, especially if there exists a permanent residue, gas chromatography (GC) was also used. The residual monomer has also been determined in samples cured under adiabatic conditions. The autocatalytic model developed by Kamal is used to analyse the curing kinetics. The final kinetic model is satisfactorily applied to dynamic and isothermal curing reactions. © 2000 Society of Chemical Industry 相似文献
140.
I. Mondragon P. M. Remiro M. D. Martin A. Valea M. Franco V. Bellenguer 《Polymer International》1998,47(2):152-158
The viscoelastic behaviour of a stoichiometric diglycidyl ether of bisphenol-A, (DGEBA), 4,4′-diaminodiphenylmethanes (DDM)s epoxy matrix modified with several amounts of poly(methyl methacrylate) (PMMA) has been studied by dynamic-mechanical analysis. Mixtures pre-cured at 80°C ranged from transparency to opacity as thermoplastic content changed from 5 to 15wt%. These changes have been attributed to variations in the ratio between polymerization rate and phase separation rate when PMMA content increased in the mixtures. When PMMA segregated from the epoxy matrix during curing, it had no influence on the crosslinking density of the epoxy phase. The clear decrease of temperature and activation energy of the β relaxation with respect to those values for the neat matrix, observed for the 5wt% PMMA-containing mixture but not for the 15wt% PMMA-containing one, are proposed to be a consequence of physical interactions between the PMMA chains and some epoxy oligomers. The dissimilar variation of the height of the ω relaxation with frequency when compared to that for the other relaxations studied, outlines the significance of physical factors influencing this relaxation. © 1998 Society of Chemical Industry 相似文献