共查询到18条相似文献,搜索用时 218 毫秒
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甲壳胺的结晶度和结晶形态 总被引:6,自引:0,他引:6
首次制得非晶甲壳胺样品,并给出了根据X射线衍射图精确计算甲壳胺结晶度的公式,计算得知甲壳胺的结晶度随脱酰度的增加(74%~85%)而增加,发现甲壳胺的结晶结构和结晶形态与制样条件有关。 相似文献
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间规立构聚丙烯的结晶度研究 总被引:3,自引:0,他引:3
Nata等用Ziegler-Nata催化剂首次合成了间规度为~50%间规聚丙烯,并对其进行了表征,指出其具有(TTGG)2螺旋构象,正交晶系,C2221空间群[1,2].近年来用茂金属催化剂合成的间规立构聚丙烯(sPP)的间规度可达93%以上,高间规... 相似文献
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广角X-射线衍射对PET结晶度的研究 总被引:6,自引:0,他引:6
应用广角X-射线衍射(WAXD)来测定高聚物的结晶度可以分为相对法(CCI、ICI)与绝对法(HWM、CPRM、Ruland)两大类,但长期以来在文献上这些方法得出的结果往往差别很大,而且WAXD与其它的方法,如DSC、ρ、NMR、IR等往往也不相一致。本文就此两问题进行了系统的研究,不仅对WAXD与DSC、ρ测定结晶度的可靠性进行了讨论,更对WAXD的各种方法中,2θ应选的范围、是否应作校正、非晶散射如何扣除、相对法自身之间的关系、各种绝对法之间的关系、相对法与绝对法的关系等进行了仔细的研究。结论是:WAXD在可靠性与重复性方面优于DSC与ρ法,而且是其它方法的根据;绝对法优于相对法,各种绝对法有利有弊,而非晶散射的合理分离是最为关键的问题。 相似文献
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ZSM-5分子筛结晶度及晶粒大小的影响因素 总被引:1,自引:0,他引:1
以硅溶胶为硅源,偏铝酸钠为铝源,用晶种法制备ZSM-5分子筛.考察了物料混合方式、陈化时间、晶化时间、晶化温度、碱度和水量等对ZSM-5分子筛相对结晶度和晶粒大小的影响.用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和激光粒度分析等对所合成样品进行了表征.结果表明:在一定的高碱度条件下形成高浓度的硅铝酸盐凝胶,才能合成出晶化良好的样品,ZSM-5分子筛是按固相机理形成的;合成ZSM-5分子筛的相对结晶度和平均颗粒度均随晶化温度的升高及硅铝酸盐凝胶浓度的增加而增大,在室温陈化24 h、180℃晶化12~24 h时相对结晶度最高,平均颗粒度基本上与陈化时间无关. 相似文献
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4.2 Ruland方法使用式(2)计算结晶度时,Ruland考虑了热运动及晶格畸变的影响,从而使算得的结晶度值较合理。在不失计算结晶度W_(c,x)数值精度的情况下,在Ruland方法的实验中可以只取具有较大衍射峰强度的S范围,就可提高计算结晶度的数值准确性,克服了其它方法必须收集尽可能大范围S内的衍射强度数据的限制。Ruland方法测定结晶度的基本公式: 相似文献
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Rojas de Gáscue B. Prin J. L. Guerra D. Urbina de Navarro C. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):343-347
This work presents a relationship between the thermal properties in different polyethylene samples analyzed by differential
scanning calorimetry (DSC). The morphology and structural changes were studied by transmission electron microscopy (TEM).
A preparative method involving surface etching was used to obtain surface replicas. The main morphological features of the
samples, characterized by lamellar structure, obtained in this work by TEM give values of mean lamellar thickness from 900
to 500 Ĺ in the highest branch content and molecular mass. Enthalpies of melting allowed to calculate crystallinity; given
values in the range from 47 to 68%.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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动态硫化EPDM/PP共混体系中PP相的结晶度及晶体结构的研究 总被引:3,自引:0,他引:3
研究了动态硫化EPDM/PP共混物中PP相的结晶度及晶体结构,同时讨论了制备工艺条件以共混物中PP相的结晶度和晶体结构的影响。结果表明:在动态硫化EPDM/PP共混物中,硫化的EPDM的分子键没有穿入PP的晶区,PP的结晶度随EPDM含量的增加而下降。提高共混温度,加入软化剂或碳黑均使共混物中PP的结晶度降低,共混时间15min时,共混物中PP相的结晶度最低,但PP的晶格不受制备工艺条件的影响。 相似文献
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热处理对聚醚醚酮晶体结构参数及结晶度的影响 总被引:7,自引:0,他引:7
采用广角X射线衍射(WAXD)方法研究了不同热处理温度下聚醚醚酮(PEEK)的晶胞参数、微晶尺寸及结晶度的变化。根据X射线散射强度理论,运用图解多重峰方法导出了以WAXD方法计算PEEK结晶度的公式;用此公式对经不同热处理的PEEK样品进行计算,结果与由密度法及量热法测定的结果具有较好的可比性。 相似文献
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The degradation of polycaprolactone (PCL) in a solution of lipase and phosphate buffer has been characterized using a combination of differential scanning calorimetry (DSC) and electron microscopy. The molecular weight of the polymer initially appeared to determine the degradation rate while the degree of crystallinity was found to increase with time. Samples of PCL were also conditioned using DSC to specify a known degree of crystallinity. This approach enabled the effects of molecular weight and degree of crystallinity on the degradation to be separated. It was observed that an increase in either molecular weight or degree of crystallinity reduced the rate of degradation. The work presented in this paper addresses a significant limitation associated with the characterization of “as received” samples and provides a more detailed understanding of the effect of polymer morphology on the degradation process. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Summary: Stereorregular polylactides such as poly (L-lactide) (PLLA) or poly (D-lactide) result from polymerization of optically pure lactides and are semicrystalline. Optically non-active poly(D,L-lactide) (PDLLA) can be regarded as random or atactic copolymers, show a random moiety distribution, and are completely amorphous. In this work three phases, comprising mobile amorphous fraction (MAF, χMA), rigid amorphous fraction (RAF, χRA) and crystalline fraction (χc) were determined in PLLA. It will be shown that RAP fraction not only elevates Tg but also increases the dynamic fragility (m) of polylactide chains around the Tg. These results agree with reported cases in which topologycal constraints inhibit longer range dynamics and suggest a smaller length scale of cooperativity of chains in confined environments. 相似文献
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Pradip K. Bhowmik Gregory Beaucage Subrata K. Bhattacharya Robert W. Lenz 《Journal of Polymer Science.Polymer Physics》1994,32(6):1023-1031
The degree of crystallinity of as-made fully aromatic, thermotropic polyesters was determined for two different series of polymers, each of which contained a symmetric monomer having either pendant phenyl groups or fused aromatic rings by the WAXD technique. All of the homopolymers had a high degree of crystallinity in spite of bulky substituents attached to the mesogenic moiety. Surprisingly, the homopolymer of 2,6-naphthalenedicarboxylic acid with each of the monomers had a higher degree of crystallinity and Tm than those of the homopolymer of terephthalic acid with each of the respective monomers. As expected, on copolymerization with 30 mol % of either 4-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid, all of the resulting copolymers had a much lower degree of crystallinity and Tm/Tf values compared to those of the respective homopolymers in each series. © 1994 John Wiley & Sons, Inc. 相似文献