毕业论文-聚乙烯树脂结构对其流延基膜硬弹性的影响.doc

摘  要：单向拉伸工艺是制备聚乙烯微孔膜的主要方法，制备具有硬弹性结构的基膜材料是单向拉伸工艺制备微孔膜的关键步骤。其中树脂结构对流延基膜的硬弹性具有重要影响。本文围绕聚乙烯树脂结构对基膜硬弹性行为的影响展开研究。我们分别考察了不同分子量大小、不同结晶行为和不同支链结构对PE流延基膜硬弹性的影响。结果发现，高分子量的HDPE在流延过程中容易形成较多的结晶成核点，在流延辊上冷却结晶时更容易形成串行排列的片晶结构，具有更好的硬弹性。HDPE基膜原料的结晶行为有所差异导致在一定牵伸比下制得的基膜的硬弹性也有所不同，并且树脂的结晶性能越好，相应制得基膜的硬弹性也越好。在HDPE中添加LDPE后，基膜晶区取向程度有所提高，但结晶度、片晶厚度均有下降，导致了PE基膜硬弹性的下降，但力学性能有所增加。在HDPE中添加LLDPE后，虽然结晶度、片晶厚度下降了，但是硬弹性几乎不变，力学性能也有所增加。当基膜经过热处理之后，基膜晶区的取向程度和结晶度都明显增加，其硬弹性结构表现得更为完善，使基膜沿纵向的拉伸强度、弹性模量和屈服应力得到一定程度的提高，并且弹性回复率也相应的提高了。但是热处理前后分子量、长链支化和短链支化对基膜硬弹性结构的影响趋势没有发生改变。

关键词：聚乙烯流延膜；硬弹性；链结构；结晶行为

Influence of Polyethylene Resin Structures on Hard Elastic Behavior of Their Cast Films

Abstract: Uniaxial stretching process is one of the main methods of preparing polypropylene microporous membranes. Preparing cast films with hard elastic behavior is key to obtain microporous membranes by uniaxial stretching process. And polyethylene resin structures have great influence on hard elastic structures and properties of their cast films. This paper was mainly about the relationship between different PE resin chain structures and hard elastic behavior of their corresponding cast films. The influence of different molecular weights, crystallization behavior and branched chain structures on hard elastic behavior of PE cast films was investigated. It was found that PE resins with high molecular weight had more nucleating sites and row-nucleated lamellar crystallization when being cast into films, and it resulted in better hard elastic properties. In a certain draw ratio, resins with different crystallization behavior leaded to different hard elastic behavior, and those with better crystallization properties, corresponding cast films had better hard elastic behavior. Adding LDPE to HDPE resin, the crystal orientation of cast films was improved while the crystallinity and lamellae thickness decreased. This reduced the hard elastic properties of cast films, but their mechanical properties enhanced. Adding LLDPE to HDPE resin, although the crystal orientation and crystallinity of cast films decreased, the hard elastic properties of films were still unchanged and their mechanical properties went up. By annealing, crystal orientation and crystallinity in cast films was increased so that films by annealing had a more perfect hard elastic structure. The tensile strength along the MD, modulus of elasticity, yield stress and elastic recovery had been improved due to the perfection of hard-elastic structure, but the data of elongation at break tended to go down.

Key words：Polyethylene cast films；Hard elastic；Chain structure；Crystallization behavior

目  录

摘  要 I

Abstract II

1 前言 1

1.1 锂离子电池隔膜的基本性能和微孔结构 1

1.2 聚烯烃微孔膜的制备工艺 2

1.3 单向拉伸工艺制备聚烯烃微孔膜的研究进展 2

1.4 聚烯烃薄膜的硬弹性 3

1.5 论文的研究内容和意义 4

2 实验部分 5

2.1 主要原料 5

2.2 主要仪器 5

2.3 实验方法 5

2.3.1 流延基膜的制备 6

2.3.2 基膜的热处理 6

2.3.3 流延基膜的表征 6

3 结果与讨论 9

3.1 树脂分子量对基膜硬弹性的影响 9

3.2 树脂结晶行为对基膜硬弹性的影响 10

3.3 树脂的长支链结构对HDPE流延基膜硬弹性的影响 12

3.4 树脂的短支链结构对HDPE流延基膜硬弹性的影响 15

3.5 热处理对PE流延基膜硬弹性的影响 17

3.5.1 热处理对线型结构HDPE基膜硬弹性的影响 17

3.5.2 热处理对长支链结构PE基膜硬弹性的影响 19

3.5.3 热处理对短支链结构PE基膜硬弹性的影响 22

4 结论 25

参考文献 26

致谢 28