Abstract:

Polyvinyl alcohol is recognized as a green degradable material because of its good performance and environmental friendliness. However, the molecular structure of polyvinyl alcohol is highly regular, and there are strong hydrogen bonds within and between molecules, resulting in its similar melting point and thermal decomposition temperature, narrow thermal processing window, difficult to thermoplastic processing and molding, and limited application field. This paper focused on the two stages before and after the finished product of polyvinyl alcohol, and systematically introduced the method of thermoplastic modification of polyvinyl alcohol in recent years. Among them, the pre-modification of polyvinyl alcohol products was copolymerization modification (modified monomers are vinyl monomers, acrylic monomers and other monomers). The pre-modification also included regulating the degree of polymerization and alcoholysis. The post-modification of polyvinyl alcohol products was divided into plasticization modification (including water and water compound plasticization system, polyol plasticization system, ionic substance plasticization system and polyphenol plasticization system) and post-reaction modification. The principle of thermoplastic modification was expounded, including the changes of steric hindrance and steric regularity of polyvinyl alcohol in the pre-modification of finished products, the interaction of subvalent bond forces between molecular chains in plasticization modification, and the formation of polyvinyl alcohol network structure in post-reaction modification. In addition, the article compared and analyzed the advantages and disadvantages of different thermoplastic modification routes. The relationship between different modified substances and thermal processing properties was introduced in detail, which provided a certain reference for choosing a suitable method to prepare thermoplastic polyvinyl alcohol. Based on the existing thermoplastic modification methods and effects of polyvinyl alcohol, it was proposed that copolymerization modification and post-reaction modification would be the main directions of the future development of polyvinyl alcohol to give it more stable thermal processing properties and broaden its application field.

Key words: polyvinyl alcohol, thermoplastic, thermal processing window, hydrogen bonding, modified

摘要：

聚乙烯醇具有良好的使用性能和环境友好性能，是公认的绿色可降解材料。但聚乙烯醇分子结构高度规整，分子内和分子间存在强氢键作用，导致其熔点和热分解温度相近，热加工窗口窄，难以热塑加工成型，应用领域受限。本文以聚乙烯醇成品前后两个阶段为重点，系统介绍了近些年聚乙烯醇热塑改性的方法。文中指出，聚乙烯醇成品前期改性为共聚改性（改性单体为乙烯类单体、丙烯酸酯类单体和其他单体）以及调控聚合度、醇解度。而聚乙烯醇成品后期改性分为增塑改性（包括水及水复配增塑体系、多元醇类增塑体系、离子类物质增塑体系和多元酚类增塑体系）以及后反应改性。文中阐述了热塑改性原理，包括成品前期改性中聚乙烯醇空间位阻和空间规整度的变化，增塑改性中分子链间次价键力的相互作用以及后反应改性中聚乙烯醇网络状结构的形成。此外，对不同热塑改性路线优缺点进行了对比分析，详细介绍了不同改性物质与热加工性能之间的关系，为选择合适的方法制备热塑性聚乙烯醇提供一定的借鉴和参考。基于现有聚乙烯醇热塑改性方法及效果，提出了共聚改性和后反应改性将是聚乙烯醇未来发展的主要方向，以赋予其更加稳定的热加工性能，拓宽应用领域。

关键词: 聚乙烯醇, 热塑性, 热加工窗口, 氢键作用, 改性