PVA纳米膜的结晶和改性研究

发布时间：2018-02-27 17:00

本文关键词： PVA 纳米膜结晶耐水性改性　出处：《东华大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚乙烯醇(PVA)作为一种具有生物相容性、可生物降解、安全环保、可加工性强等优良性质的高分子,广泛的应用于医疗卫生、化妆品工业、薄膜包装业等。目前,对PVA纳米膜中的结晶过程、机械性质及其他物理化学性质认识还刚刚起步。在本论文中,我们通过红外光谱在线研究了PVA分子受限在纳米尺度薄膜中的结晶过程,并揭示了结晶机理,利用红外数据计算PVA的结晶度,方法准确便捷,减小了实验中的困难;同时利用结晶、化学交联、物理交联以及两种方法的结合对PVA纳米膜进行了改性,将对PVA其他材料的改性方法有选择地应用于PVA纳米膜上,并制备了具有较高耐水性和机械性能的PVA纳米膜。主要获得的结果如下:(1)通过加热可以提高PVA纳米膜的结晶度,且操作简单,纳米膜的耐水性、强度均有大幅改善。在加热处理中我们发现:当达到PVA玻璃化转变温度时才会出现结晶,且在整个过程中PVA的结晶度呈上升趋势,降温阶段结晶对薄膜的结晶度贡献较大。对比不同温度处理的纳米膜的结晶度发现:在一定温度范围内,PVA纳米膜的结晶度随着加热温度的升高而增加;为了提高结晶度,加热温度不宜超过190 oC。(2)耐水试验结果说明结晶后的PVA薄膜的耐水性提高,可长时间浸渍于水中而不致完全溶解,且耐水性随着结晶度的升高而增强;在纳米膜的拉伸测试中发现,薄膜的弹性模量随着结晶度的升高而增加,而断裂伸长率却随之减小,薄膜变得硬而脆。(3)PVA纳米膜与戊二醛交联后进行加热处理,加热加固了已有的网络结构,薄膜的耐水性增强。先加热处理PVA纳米膜再进行交联改性,薄膜可继续发生交联反应,但程度较小。两种方法制备的薄膜均可以在水中保存30天以上,对比两种方法处理的纳米膜的耐水性,发现交联后再进行加热处理的纳米膜的耐水性更佳。(4)向PVA中添加三聚氰胺,两种成分可以通过氢键形成物理交联,获得PVA/MA纳米膜。在PVA/MA纳米膜的拉伸试验中我们发现即使加入少量三聚氰胺就可使薄膜的弹性模量、断裂伸长率提高,而且随着三聚氰胺含量的增加薄膜的强度和韧性也随之增加,而且在拉伸过程中PVA/MA纳米膜有较长的屈服,这在实际应用中具有重要意义。(5)PVA/MA纳米膜经过加热可发生结晶,红外图谱显示的结晶过程与纯PVA的结晶过程一致。结晶后的PVA/MA纳米膜耐水性也得到很大提高;将不同结晶度的PVA/MA纳米膜进行拉伸测试,结果显示纳米膜的结晶度越高弹性模量越大,最高可达纯PVA纳米膜的50倍左右,在实际应用中可以将PVA/MA纳米膜适当加热来提高其力学性能。
[Abstract]:Polyvinyl alcohol (PVA) is a kind of polymer with biocompatibility, biodegradability, safety and environmental protection, strong processability and so on. It is widely used in medical and health, cosmetics industry, film packaging industry, etc. At present, The crystallization process, mechanical properties and other physical and chemical properties of PVA nanocrystalline films are still in its infancy. In this thesis, we have studied the crystallization process of PVA molecules confined in nanoscale films by infrared spectroscopy. The crystallization mechanism was revealed, the crystallinity of PVA was calculated by infrared data, the method was accurate and convenient, and the difficulty in experiment was reduced, and the PVA nanofilms were modified by crystallization, chemical crosslinking, physical crosslinking and the combination of the two methods. The modification methods of other PVA materials were selectively applied to the PVA nanofilm, and the PVA nanofilms with high water resistance and mechanical properties were prepared. The main results obtained are as follows: 1) the crystallinity of PVA nanofilms can be improved by heating. In the heating treatment, we found that the crystallization occurs only when the glass transition temperature of PVA is reached, and the crystallinity of PVA increases in the whole process. By comparing the crystallinity of the films treated at different temperatures, it is found that the crystallinity of PVA nanofilms increases with the increase of heating temperature in a certain temperature range, and in order to improve the crystallinity of the films, the crystallinity of PVA nanocrystalline films increases with the increase of heating temperature. The results of water resistance test show that the water resistance of PVA films after crystallization is improved and can be impregnated in water for a long time without being completely dissolved, and the water resistance increases with the increase of crystallinity. In the tensile test, it was found that the elastic modulus of the film increased with the increase of crystallinity, but the elongation at break decreased, and the film became hard and brittle after crosslinking with glutaraldehyde, and the film was heated after crosslinking with glutaraldehyde. By heating and strengthening the existing network structure, the water resistance of the film is enhanced. The film can be crosslinked and modified by adding heat treatment to the PVA nano-film, and then the film can continue to undergo cross-linking reaction. The films prepared by both methods can be preserved in water for more than 30 days. It was found that when melamine was added to PVA by adding melamine to the PVA, the two components could be physically crosslinked by hydrogen bond. In the tensile test of PVA/MA nano-film, we found that even adding a small amount of melamine can increase the elastic modulus and elongation at break of the film. Moreover, with the increase of melamine content, the strength and toughness of the films also increased, and the PVA/MA nanofilms had a longer yield during the stretching process, which is of great significance in practical application. After heating, the PVA/MA / MA nanocrystalline films can crystallize. The crystallization process showed by IR spectra was consistent with that of pure PVA. The water resistance of PVA/MA nanocrystalline films after crystallization was also greatly improved. The tensile tests of PVA/MA nanocrystalline films with different crystallinity were carried out. The results show that the higher the crystallinity, the greater the elastic modulus, and the maximum is about 50 times of that of pure PVA film. In practical application, the mechanical properties of PVA/MA nanofilms can be improved by heating them properly.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O632.31;TB383.2

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