本文關(guān)鍵詞： PVA 納米膜 結(jié)晶 耐水性 改性　出處：《東華大學》2017年碩士論文　論文類型：學位論文

【摘要】：聚乙烯醇(PVA)作為一種具有生物相容性、可生物降解、安全環(huán)保、可加工性強等優(yōu)良性質(zhì)的高分子,廣泛的應用于醫(yī)療衛(wèi)生、化妝品工業(yè)、薄膜包裝業(yè)等。目前,對PVA納米膜中的結(jié)晶過程、機械性質(zhì)及其他物理化學性質(zhì)認識還剛剛起步。在本論文中,我們通過紅外光譜在線研究了PVA分子受限在納米尺度薄膜中的結(jié)晶過程,并揭示了結(jié)晶機理,利用紅外數(shù)據(jù)計算PVA的結(jié)晶度,方法準確便捷,減小了實驗中的困難;同時利用結(jié)晶、化學交聯(lián)、物理交聯(lián)以及兩種方法的結(jié)合對PVA納米膜進行了改性,將對PVA其他材料的改性方法有選擇地應用于PVA納米膜上,并制備了具有較高耐水性和機械性能的PVA納米膜。主要獲得的結(jié)果如下:(1)通過加熱可以提高PVA納米膜的結(jié)晶度,且操作簡單,納米膜的耐水性、強度均有大幅改善。在加熱處理中我們發(fā)現(xiàn):當達到PVA玻璃化轉(zhuǎn)變溫度時才會出現(xiàn)結(jié)晶,且在整個過程中PVA的結(jié)晶度呈上升趨勢,降溫階段結(jié)晶對薄膜的結(jié)晶度貢獻較大。對比不同溫度處理的納米膜的結(jié)晶度發(fā)現(xiàn):在一定溫度范圍內(nèi),PVA納米膜的結(jié)晶度隨著加熱溫度的升高而增加;為了提高結(jié)晶度,加熱溫度不宜超過190 oC。(2)耐水試驗結(jié)果說明結(jié)晶后的PVA薄膜的耐水性提高,可長時間浸漬于水中而不致完全溶解,且耐水性隨著結(jié)晶度的升高而增強;在納米膜的拉伸測試中發(fā)現(xiàn),薄膜的彈性模量隨著結(jié)晶度的升高而增加,而斷裂伸長率卻隨之減小,薄膜變得硬而脆。(3)PVA納米膜與戊二醛交聯(lián)后進行加熱處理,加熱加固了已有的網(wǎng)絡(luò)結(jié)構(gòu),薄膜的耐水性增強。先加熱處理PVA納米膜再進行交聯(lián)改性,薄膜可繼續(xù)發(fā)生交聯(lián)反應,但程度較小。兩種方法制備的薄膜均可以在水中保存30天以上,對比兩種方法處理的納米膜的耐水性,發(fā)現(xiàn)交聯(lián)后再進行加熱處理的納米膜的耐水性更佳。(4)向PVA中添加三聚氰胺,兩種成分可以通過氫鍵形成物理交聯(lián),獲得PVA/MA納米膜。在PVA/MA納米膜的拉伸試驗中我們發(fā)現(xiàn)即使加入少量三聚氰胺就可使薄膜的彈性模量、斷裂伸長率提高,而且隨著三聚氰胺含量的增加薄膜的強度和韌性也隨之增加,而且在拉伸過程中PVA/MA納米膜有較長的屈服,這在實際應用中具有重要意義。(5)PVA/MA納米膜經(jīng)過加熱可發(fā)生結(jié)晶,紅外圖譜顯示的結(jié)晶過程與純PVA的結(jié)晶過程一致。結(jié)晶后的PVA/MA納米膜耐水性也得到很大提高;將不同結(jié)晶度的PVA/MA納米膜進行拉伸測試,結(jié)果顯示納米膜的結(jié)晶度越高彈性模量越大,最高可達純PVA納米膜的50倍左右,在實際應用中可以將PVA/MA納米膜適當加熱來提高其力學性能。
[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.
【學位授予單位】：東華大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O632.31;TB383.2

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