南京工业大学本科生毕业论文

PVDF膜材料表面的耐碱老化研究

摘要

聚偏氟乙烯是一种半结晶聚合物，具有较强的疏水性，能流延成膜，易受到有机物，特别是蛋白质的吸附而造成膜污染。针对膜污染，用较高浓度的NaOH碱液在高温下对膜进行清洗。但在清洗过程中，我们发现PVDF在碱液下逐渐变黄甚至发黑，PVDF的膜结构被破坏，减短了PVDF膜的使用寿命。本实验正是基于此，采用改变PVDF表面结晶形态的方法对PVDF进行改性，从而提高其耐碱性。

PVDF常见的晶体结构主要有三种：β、α、γ晶型。而溶剂和不同温度对膜结晶性能以及各种晶型的产生都有比较宏观的影响。根据文献及前期摸索，实验主要从以下三方面进行：成膜工艺、结晶形态、表面形貌结构对PVDF膜耐碱性的影响。

我们着重研究了PVDF膜材料在不同亲核试剂（氢氧根、乙胺）进攻下的脱氟降解过程，以及表面结构对此界面层脱氟降解反应的影响。

在相同的侵蚀环境下，PVDF溶剂膜脱氟降解速度和程度要远远高于PVDF熔融膜。溶剂膜老化速度要快于熔融膜。含α晶型较多的PVDF膜耐碱老化性能明显要强于含α晶型多的PVDF膜。表面排布较规整的样品更耐碱老化。

关键词：聚偏氟乙烯 耐碱性 结晶形态 脱氟降解

I

Abstract

Alkali resistance of Poly(vinylidene fluoride) film

Abstract

PVDF is a semi - crystalline polymer, with strong hydrophobicity, cast film, vulnerable to organic compounds, especially protein adsorption and membrane fouling caused. Membrane fouling, with a high concentration of NaOH alkaline solution under high temperature on membrane cleaning. But in the process of cleaning, we find PVDF lye gradually turn yellow or even black, PVDF membrane structures are destroyed, reduced the use of PVDF membrane life. This experiment is based on this, using the change of surface morphology of PVDF methods to be modified, thereby improving its alkali resistance.

But with different solvents and temperature on properties of membrane crystallization and Crystal have a wider impact. According to historical and early exploring, the experiment from the following three main areas : film forming process, Crystal morphology, effect of surface morphology structure on alkali resistance of PVDF membrane.

We focus on PVDF membrane material in different nucleophiles hydroxyl, ethylamine defluorination process under attack, and surface structure on the degradation effects of fluorine gas - fluid interface.

Under the same erosion environment, solvent PVDF membrane defluorination degradation level of speed and much higher than the melting film of PVDF. Solvent film aging faster than melting film. PVDF membrane containing α Crystal more aging properties of alkali – resistant noticeably stronger than α crystal of PVDF membrane. Alkali resistance of surface layout more structured samples more aging.

Key words: poly(vinylidene fluoride); alkali resistance;crystal; defluorination of degradation

II

南京工业大学本科生毕业论文

目 录

摘要 ............................................................................................................................ I Abstract .....................................................................................................................II 第一章 文献综述 ..................................................................................................... 1

1.1引言 .................................................................................................................................... 1 1.2 PVDF与碱的脱氟反应机理 ............................................................................................. 2

1.2.1反应原理 .................................................................................................................. 2 1.2.2 PVDF与碱反应的FT-IR表征 ............................................................................... 3 1.2.3 PVDF与碱反应的拉曼表征 ................................................................................ 4 1.2.4 ESR ........................................................................................................................... 5 1.3PVDF晶型结构 .................................................................................................................. 8

1.3.1 α晶型 .................................................................................................................... 8 1.3.2 β晶型 .................................................................................................................... 8 1.3.3 γ晶型 .................................................................................................................... 9 1.4 实验方案与研究方向 ..................................................................................................... 11

第二章 实验样品制备部分 ................................................................................. 12

2.1 主要原料和仪器 ............................................................................................................. 12

2.1.1实验原料与试剂 .................................................................................................... 12 2.1.2 实验仪器与设备 ................................................................................................. 12 2.2 膜制备 ............................................................................................................................. 12

2.2.1 熔融铸膜 ............................................................................................................... 12 2.2.2溶剂铸膜 ................................................................................................................ 13

第三章 结果讨论 ................................................................................................... 14

3.1溶剂膜在氢氧根和乙胺进攻下的脱氟降解反应 .......................................................... 14

3.1.1通过ΔL值表征PVDF溶剂膜表面脱氟降解反应程度 .................................... 14 3.1.2 FTIR-ATR分析 ..................................................................................................... 16

III