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利用溶液的光散射,测定高聚物的分子量和分子形态参数,在目前已经得到广泛的应用。光散射实验的最大困难在于测定液中尘埃颗粒的干扰,实验要求测定的溶液和溶剂都需要经过特殊的除尘处理,以达到光学洁净。最常用的除尘方法有高速离心和过滤,但是在实验中还需要将经过除尘处理的液体,从一个容器转换到另一个容器,或需要在貯液瓶中貯藏和在测定池中稀释或加浓,因此对这些容器也就同样需要予以除尘处理。 Thurmond很早就报导了他所设计的这类仪器。最近Schipmann和Farber又提出了新的设计。 相似文献
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The chemical structure of copolymer formed in the transesterification of PPSQ/PET blendsduring melt-processing is deduced from the ~1H-NMR spectra. The transesterification extent ofthis blend is interpreted by the changes of crystalline melting peak in DSC thermograms of the in-soluble products containing unreacted PET and some block PPSQ segments. Effects of composi-tion of blend ladderlike regularity of PPSQ on the reaction extent have also been discussed.Inclusion of some block PPSQ segments in PET has no influence on the crystalline morphology ofPET. 相似文献
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本文研究了不同组成聚苯乙烯、聚甲基丙烯酸甲酯混合物甲苯溶液和聚苯乙烯在不同浓度的聚甲基丙烯酸甲酯-甲苯体系中的光散射。试样聚苯乙烯是经过二次重复分级的级分;聚甲基丙烯酸甲酯是经过三次重复分级的级分。由于聚甲基丙烯酸甲酯的折光指数和甲苯相同,聚甲基丙烯酸甲酯分子对溶液的散射光强没有贡献。从90°,45°和135°三个角度的散射光强测定计算得到聚苯乙烯级分的重均分子量和均方末端距,在所有情况下都相同,而曲綫斜率,受聚甲基丙烯酸分子的存在而降低。实验结果表明溶液中聚甲基丙烯酸甲酯的存在,对聚苯乙烯的〈M〉_w和〈h~2〉~(1/2)_z没有影响。 相似文献
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The dynamic mechanical modulus at 25℃for blends of segmented polyurethanes with PVC was studied by using suitable mechanics models of multi-component systems. The analysis indicates that the blend morphology was mainly determined by soft segment structure of polyurethanes. The PPO-PU/PVC blends show typical two-phase morphology and their modulus-composition relations may be described by Halpin-Tsai model for domain-matrix two-phase systems.While the PCL-PU / PVC, PTMA-PU/PVC and PTMO-PU/PVC blends fit the Kerner's packed grain composite model. These results may imply that the modulus-composition relationship is sensitive to the interactions between the components and the mixture morphology of the blends. 相似文献
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聚乙烯由于耐溶剂性较好,一般只能在较高的温度下,溶于少数溶剂中,如对二甲苯,四氫萘,十氫萘和α-氯代萘等。对低压聚乙烯来说,更由于它的结晶度高,溶解温度相应地必须提高到125℃以上。因此无论作分子量的测定或者分级实验,操作上都增加了不少困难。例如粘度测定除了需对粘度计作适当设计外,还必须考虑氧对聚乙烯的降解作用。渗透压测定 相似文献
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以苯酚为溶剂,甲醇为沉淀剂将三个聚壬酰胺试样(??各为20400,12900和7100)分级沉淀.每一试样至少经过二次分级,共得到二十级份.取其中七个级份测定其数均分子量及特性粘数.粘度测定在25℃,溶剂用苯酚-乙酸(2∶1重量比).在分子量4300-20000内,得到下列特性粘数-分子量关系: [η]=7.52×10~(-3)M~(0.96)ml/g M=200[η]-360 苯酚-乙酸(2∶1重量比)混合溶剂容易纯化且不引起聚壬酰胺的降解,能溶解尼龙-6,66,7,9和11,可作聚酰胺粘度测定的普适溶剂. 相似文献
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The steric tacticity of polyphenylsilsesquioxanes is discussed based on both structure transformation consideration and the results of calculations, X-ray diffraction patterns, fluorescence emission spectroscopy, and scanning electron microscopy. All of the results show that cis-isotactic conformation is the most probable one for ladderlike polymer polyphenylsilsesquioxane though other conformations such as cissyndiotactic may also be present in the macromolecules depending upon the preparation conditions. 相似文献