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首页> 外文学位 >Structure development of polypropylenes of varying stereoregular form and tacticity in melt spinning, tubular blown film extrusion and injection molding.
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Structure development of polypropylenes of varying stereoregular form and tacticity in melt spinning, tubular blown film extrusion and injection molding.

机译：在熔体纺丝，管状吹膜挤出和注塑成型中，具有不同立体规整度和立构规整度的聚丙烯的结构开发。

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摘要

Polypropylene has become an important commercial thermoplastic since the isotactic form was first synthesized in the 1950's by Natta and his coworkers using Ziegler's catalysts. In recent years, new types of polypropylenes different than the existing Ziegler-Natta polypropylenes have also been commercially available through the application of the improved catalysts, i.e. metallocene. These include isotactic polypropylenes possessing lower stereoregularities and syndiotactic polypropylene.; In this dissertation, we study structure development in processing these new polypropylenes and conventional high tacticity isotactic polypropylenes. We begin with the study of formation of structure in crystallization from quiescent melts and investigation of the crystallization kinetics of these polypropylenes. These are carried out by both isothermal and non-isothermal experiments. Then, we turn to the study of structure development during processing of these polymers. This is carried out in three major polyolefin processing processes: (i) melt spinning, (ii) tubular blown film extrusion and (iii) injection molding.; The crystal structure and orientation of fabricated samples were characterized by wide angle X-ray diffraction (WARD), birefringence and differential scanning calorimetry (DSC).; We seek to correlate the formation of structure and orientation development with processing conditions (e.g. stress field and cooling rate) and material characters (e.g. tacticity and crystallization rate) and find processing-structure-properties relationships in processing these polymers.
机译：自从Natta及其同事在1950年代首先使用齐格勒的催化剂合成了全同立构形式以来，聚丙烯已成为重要的商业热塑性塑料。近年来，通过使用改进的催化剂，即茂金属，与现有的齐格勒-纳塔聚丙烯不同的新型聚丙烯也已经商业化。这些包括具有较低立体规整度的等规聚丙烯和间规聚丙烯。在本文中，我们研究了在加工这些新型聚丙烯和常规高立构规整聚丙烯中的结构开发。我们首先研究静态熔体结晶过程中结构的形成，并研究这些聚丙烯的结晶动力学。这些通过等温和非等温实验进行。然后，我们转向研究这些聚合物在加工过程中的结构。这是在三个主要的聚烯烃加工工艺中进行的：（i）熔融纺丝，（ii）管状吹膜挤出和（iii）注塑成型;用广角X射线衍射（WARD），双折射和差示扫描量热法（DSC）表征所制备样品的晶体结构和取向。我们寻求将结构和取向发展的形成与加工条件（例如应力场和冷却速率）和材料特性（例如立构规整度和结晶速率）相关联，并找到加工这些聚合物的加工-结构-性能关系。

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  • 作者

    Choi, Dongman.;

  • 作者单位

    The University of Akron.;

  • 授予单位 The University of Akron.;
  • 学科 Engineering Materials Science.; Plastics Technology.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 265 p.
  • 总页数 265
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;整形外科学（修复外科学）;
  • 关键词

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