PMMA-PET共混体系流变性能

研究了PMMA含量小于7．5％的PMMA—PET共混体系的流变性能．结果表明，共混体系为切力变稀的非牛顿流体，随着共混体系中PMMA组分的增加，非牛顿指数呈减小趋势，粘度有一定下降；在280℃低剪切应力时，ηa随着PMMA组分的增加而上升，在高剪切应力时，则相反；共混体系的粘流活化能基本上都大于纯PET。     

Relaxation processes in a glassy polymer containing methanol molecules

The interaction of small guest molecules with the molecular degrees of freedom of a glassy polymer matrix is investigated, i.e. (i) the dynamics of these guest molecules and (ii) their effect on the secondary ‘β’ and main ‘’ relaxations of the host polymeric matrix. The system considered here is the glassy poly(methyl metacrylate) modified by introduction and desorption of methanol. The dynamics of the system is observed by means of low-frequency mechanical and wide band dielectric spectroscopies. The presence of small molecules in the PMMA glassy matrix induces several effects, namely (i) a strong relaxation peak develops at low temperature (near 120 K at 1 Hz and called _m in the following), (ii) the strength of the β relaxation is increased while the temperature of the maximum shifts towards the low temperatures, (iii) a sharp peak appears superimposed on the β peak, and finally (iv) the relaxation shifts towards the low temperatures. Dielectric and mechanical spectroscopies results are in agreement and make it possible to capture the dynamical behavior in a wide frequency range (eight decades). The experimental results are explained on the basis of physical concepts recently introduced in the physics of glassy matter: cooperativity and nanoheterogeneity. In particular, the low-temperature relaxation process _m is attributed to cooperative motions in methanol clusters which form in the nanoheterogeneous polymeric matrix, in agreement with small angle X-rays scattering and low-frequency Raman scattering observations recently reported.     

Positron annihilation studies of nanoholes and microphase formation control of a PMMA+MMA+TEGDMA system

Positron annihilation lifetime spectroscopy (PALS) was applied for the study of a set of PMMA (polimethyl-methacrylate)+MMA (methyl-methacrylate)+TEGDMA (triethyleneglycol-dimethacrylate) blends prepared by two synthesis routes (standard and phase separation methods). The aim was to investigate the correlation between free volume and miscibility of the compounds. PALS measurements were performed in order to determine contents and sizes of free volume on the ‘standard’ and ‘phase-separation’ polymers; important differences in the behavior of the free volume composition curves were found, which are explained in terms of the formation of microregions in the phase separation material. When considering simple binary interchain interaction, the mean free volume hole fraction in a blend was computed in terms of an interaction parameter (β) that might be correlated to the Flory-Huggins interaction parameter (χ). This suggests that local free volume properties of polymer in blends are very important for local packing and segmental arrangements. We have re-encountered the task of defining miscibility depending upon the scale of observation: we observed distinct phases in the micrometer scale while still nothing can be discerned in the nanometer scale. We conclude that it is possible to produce a PMMA+TEGDMA blend with the presence of a low fraction of MMA/TEGDMA copolymer situated at the interphase between the PMMA and TEGDMA regions allowing a higher degree of compatibility of the components.     

PMMA模塑料流变性能与挤出制板技术研究

用Ｉｎｓｔｒｏｎ３２１１流变仪在模拟挤出条件下，测定了４种牌号ＰＭＭＡ模塑料（中国）ＹＭ－１，德国７Ｈ、意大利９Ｅ、日本ＨＡ）的表观粘度、流支活化能和流变曲线。考究了其熔体属于非牛顿性的假塑性流体，其熔体的表观粘度与温度的关系符合Ａｒｒｈｅｎｉｕｓ规律，讨论了影响其流变性能的几种因素，并联系抗出成型的特点予以分析。因此所得结论对ＰＭＭＡ模塑料挤出制板工艺有一定的指导意义。     

用介电方法研究COPU/PMMA交联共聚物的转变与松弛

用TRS-10C型介电损耗仪,在不同频率,-180℃～170℃范围内测得COPU/PMMA交联共聚物的介电损耗谱。计算了各松弛过程的活化能,考察了组成和交联密度对分子运动、相容性及形态结构的影响。结果表明,COPU/PMMA交联共聚物是个半相容体系,其相容性随PMMA含量的增加和交联密度的减小而变坏。介电损耗谱上的次级松弛是COPU链段运动的贡献。界面极化区松弛谱的各点温度和频率的关系符合Arrhenius方程,各点温度和其高温侧松弛曲线线性部分斜率的大小可以反映相容性的好坏。     

Failure criteria for linear elastic materials with U-notches

This paper provides a simple, albeit accurate, criterion for prediction of the rupture loads of brittle, or quasi-brittle, U-notched samples, where linear elastic fracture mechanics is not applicable because blunted notches do not exhibit stress singularities. Good agreement is found between numerical predictions and experimental results. The results of fracture tests from 18 different ceramic materials and a polymer (at − 60°C) are summarized and are used as a reference for checking the fracture criterion. Seven fracture criteria are reviewed and it is shown that all can be recast into the proposed criterion.     

［Bmim］PF6离子液体中微波辅助制备纳米TiO2/PMMA及其光催化活性

微波加热法合成 ［Bmim］PF₆离子液体,以该离子液体为反应介质,在微波辐射条件下制备纳米TiO₂/PMMA复合材料,并在高压汞灯下用甲基橙溶液对其进行光催化降解性能测试,并用XRD、IR、SEM、TG和BET等对该复合材料的结构进行测试和表征。结果表明,制备TiO₂/PMMA复合材料的最佳条件：［Bmim］PF₆ 2.0 mL,钛酸丁酯与甲基丙烯酸甲酯的体积比为3.4∶1.0,微波辐射功率700 W,反应温度80 ℃,反应时间35 min。用［Bmim］PF₆离子液体作反应介质,制备的TiO₂/PMMA复合材料不需高温焙烧就表现出极高的光催化活性,对甲基橙降解率在1 h可达到99.2%,活性明显优于用［Bmim］BF₄离子液体作反应介质时所制备的同种材料的活性。     

Miscibility of polymethylmethacrylate and polyethyleneglycol blends in tetrahydrofuran

The miscibility of polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran (THF) has been investigated by viscosity, density, refractive index, and ultrasonic velocity studies. Various interaction parameters such as polymer–solvent and blend–solvent interaction parameters and heat of mixing have been calculated using the viscosity, density, and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in THF in the entire composition range. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and PEG blends in THF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

千兆位塑料光纤以太示范网络

文章介绍了所组建的全氟树脂塑料光纤千兆以太网的设计方案、设备选择及安装，给出了网络的性能测试数据，分析了全氟树脂塑料光纤及其所构筑的千兆以太网存在的问题，分析了全氟树脂塑料光纤千兆以太网的应用前景，提出了我国应加紧该领域研究的建议。     

多孔硅-PMMA/DR1复合膜制备方法的研究

用直接浸泡、匀胶机涂布和超声波三种方法在多孔硅中嵌入了聚甲基丙烯酸甲酯/分散红1(PMMA/DR1),制备出多孔硅有机材料复合薄膜.研究了多孔硅孔隙率、匀胶机转速和PMMA甲苯溶液浓度等参量对PMMA/DR1嵌入多孔硅的影响.分析了嵌入PMMA/DR1后多孔硅的荧光及样品稳定性的变化情况.