摘  要：單向拉伸工藝是制備聚乙烯微孔膜的主要方法，制備具有硬彈性結(jié)構(gòu)的基膜材料是單向拉伸工藝制備微孔膜的關(guān)鍵步驟。其中樹脂結(jié)構(gòu)對流延基膜的硬彈性具有重要影響。本文圍繞聚乙烯樹脂結(jié)構(gòu)對基膜硬彈性行為的影響展開研究。我們分別考察了不同分子量大小、不同結(jié)晶行為和不同支鏈結(jié)構(gòu)對PE流延基膜硬彈性的影響。結(jié)果發(fā)現(xiàn)，高分子量的HDPE在流延過程中容易形成較多的結(jié)晶成核點(diǎn)，在流延輥上冷卻結(jié)晶時更容易形成串行排列的片晶結(jié)構(gòu)，具有更好的硬彈性。HDPE基膜原料的結(jié)晶行為有所差異導(dǎo)致在一定牽伸比下制得的基膜的硬彈性也有所不同，并且樹脂的結(jié)晶性能越好，相應(yīng)制得基膜的硬彈性也越好。在HDPE中添加LDPE后，基膜晶區(qū)取向程度有所提高，但結(jié)晶度、片晶厚度均有下降，導(dǎo)致了PE基膜硬彈性的下降，但力學(xué)性能有所增加。在HDPE中添加LLDPE后，雖然結(jié)晶度、片晶厚度下降了，但是硬彈性幾乎不變，力學(xué)性能也有所增加。當(dāng)基膜經(jīng)過熱處理之后，基膜晶區(qū)的取向程度和結(jié)晶度都明顯增加，其硬彈性結(jié)構(gòu)表現(xiàn)得更為完善，使基膜沿縱向的拉伸強(qiáng)度、彈性模量和屈服應(yīng)力得到一定程度的提高，并且彈性回復(fù)率也相應(yīng)的提高了。但是熱處理前后分子量、長鏈支化和短鏈支化對基膜硬彈性結(jié)構(gòu)的影響趨勢沒有發(fā)生改變。

關(guān)鍵詞：聚乙烯流延膜；硬彈性；鏈結(jié)構(gòu)；結(jié)晶行為

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  錄

摘  要 I

Abstract II

1 前言 1

1.1 鋰離子電池隔膜的基本性能和微孔結(jié)構(gòu) 1

1.2 聚烯烴微孔膜的制備工藝 2

1.3 單向拉伸工藝制備聚烯烴微孔膜的研究進(jìn)展 2

1.4 聚烯烴薄膜的硬彈性 3

1.5 論文的研究內(nèi)容和意義 4

2 實(shí)驗(yàn)部分 5

2.1 主要原料 5

2.2 主要儀器 5

2.3 實(shí)驗(yàn)方法 5

2.3.1 流延基膜的制備 6

2.3.2 基膜的熱處理 6

2.3.3 流延基膜的表征 6

3 結(jié)果與討論 9

3.1 樹脂分子量對基膜硬彈性的影響 9

3.2 樹脂結(jié)晶行為對基膜硬彈性的影響 10

3.3 樹脂的長支鏈結(jié)構(gòu)對HDPE流延基膜硬彈性的影響 12

3.4 樹脂的短支鏈結(jié)構(gòu)對HDPE流延基膜硬彈性的影響 15

3.5 熱處理對PE流延基膜硬彈性的影響 17

3.5.1 熱處理對線型結(jié)構(gòu)HDPE基膜硬彈性的影響 17

3.5.2 熱處理對長支鏈結(jié)構(gòu)PE基膜硬彈性的影響 19

3.5.3 熱處理對短支鏈結(jié)構(gòu)PE基膜硬彈性的影響 22

4 結(jié)論 25

參考文獻(xiàn) 26

致謝 28