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The crystallization process of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA)and PEO/poly(vinyl acetate) (PVAc) blends has been characterized by Fourier Transform Infrared(FTIR) spectra in conjunction with Differential Scanning Calorimeter (DSC) measurements. Thecrystallinity of PEO varies consistently with PEO content in PEO/PVAc blends and the PEO/PMMAblends containing 50 wt% or less PMMA. For the PEO/PMMA blends containing 60 wt% ormore PMMA, the crystallinity of PEO decreases more than PEO content but develops with crystal-lization time. These results can be explained in terms of difference between the crystallization tem-perature (T_c) and glass transition temperature (T_g) of the blends as a function of content of amorphouscomponent. 相似文献
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通过快速淬火实验,直接观察到聚醚氨酯中由硬段N—H基与软段—O—形成氢键的N—H伸缩振动谱带位于约3295cm~(-1),低于与硬段本身C=O形成氢键的N—H伸缩振动谱带(约3330cm~(-1))。这两种氢键键连的N—H伸缩振动谱带的位置从聚醚氨酯-四氢呋喃溶液的红外光谱得到证实。在此基础上讨论了三种聚醚氨酯试样的红外光谱中N—H伸缩振动谱带的差异。 相似文献
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聚醚氨酯的微区形态 总被引:2,自引:0,他引:2
<正> 聚醚氨酯热塑弹性体是属于(AB)n类型的线型多嵌段共聚物,包括交替的硬段和软段单元.自从1966年Cooper和Tobolsky首先提出聚氨酯具有微相分离的本体结构之假设以后,至今已有大量文献报道了这类材料结构形态与性能关系的研究结果. Wilkes和Koberstein等使用SAXS研究了聚氨酯体系的形态特征.一般认为,聚氨酯材料的微相结构包括一个叠层状或类似叠层状形态,由相分离的软段和硬段组成,平均尺寸为100A的数量级,在软硬段微区之间还存在一相混合的过渡区,其厚度可以从几个埃至几十个埃.然而,SAXS虽然能够高分辨地给出多相体系相分离情况的定 相似文献
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近年来合成纤维已经得到了极其广泛的应用,然而对于纤维的结构到目前为止还没有能够彻底阐明,根据一般从熔融体纺丝的过程可知,聚合物首先是从熔融体形成丝,然后在一定条件下经过拉伸而生成高度取向的纤維。大量的实验事实証明,結晶高聚物从熔融体結晶时通常都是形成球晶,因此从拉伸丝到形成纤维的过程很可能与球晶的形变相联系,然而許多作者在研究球晶的形变和纤維的結构时都没有注意到这点,他们只是分别地研究纤維的結构和球晶的形变,没有进一步将它們联系起来进行研究,因此从研究纤維所得的結果很难加以解释,例如,为什么在取向纤維中还存在完整的球晶?为什么纤維中存在许多空洞?钎維中的結构单元是什么?以及纤維中的結构如何从熔块中的 相似文献
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Melt blends of poly(ethylene oxide) (PEO) and poly(vinyl acetate (PVAc) were prepared andstudied by Torsional Pendulum Analysis (TPA) and Fourier Transform Infrared (FTIR). Two glasstransitions were found in these blends. The lower T_g corresponds to the segmental motion in thepure PEO. The dependence of the position and broadness of the higher T_g on composition of theblends indicates that the two components are compatible in the amorphous phase with micro-hetero-geneity. These T_g values observed from mixed PVAc/PEO phase are much higher than that calculatedfrom Fox equation. The comparison of the blends quenched and annealed from melt implies thatPVAc mixed with PEO at the segmental level on molten state and the deviation of T_g values fromFox equation could be due to variation of the blend's composition by crystallization of part of thePEO component. Further indication that the blends are compatible down to the level of chain segments and thatthere are specific interactions between PVAc and PEO molecules comes from the analysis of FTIRspectra of the blends and the solution of PVA in diethylene glycol dimethyl ether. 相似文献