水与超临界二氧化碳流体的相互作用及对聚乙烯醇发泡过程和泡孔结构的调控机理

聚乙烯醇（PVA）泡沫材料是最具发展潜力的生物、医用和环保材料之一，现有的溶液法工艺复杂、成本高、污染大。热塑加工水发泡是PVA基泡沫材料的绿色制备新技术，但水蒸汽压低、饱和蒸汽温度高，泡孔孔结构和性能尚需进一步改善。本项目拟利用超临界二氧化碳的气液双重特性以及与水、PVA的相容性，与水为共发泡剂，改善热塑加工PVA基泡沫材料发泡过程及泡孔结构；研究温度、压力及剪切等外场作用下scCO2与水的相互作用，以及水、scCO2与PVA的相互作用，scCO2、水的结构、状态以及相行为；泡孔的成核、生长、形成和调控机理；通过具有自主知识产权的适宜于scCO2流体/水混合发泡剂热塑加工PVA的挤出发泡装置，制备泡孔结构均匀、综合性能优良的生物医用PVA微孔泡沫材料和具有本征阻燃特征的无卤阻燃PVA泡沫材料，为PVA泡沫材料热塑发泡提供新原理、新方法，具有重要理论和实际意义。

Poly (vinyl alcohol) (PVA) foam has been a promising material with wide applications in biology, medicine and eco-friendly materials, however, the existing solution method for PVA processing appears complex process, high cost and severe pollution. The thermal processing using water as plasticizer and blowing agent is a novel technology for preparation of PVA foam while the structure and properties of foam need to further improve due to the low water vapor pressure and high saturated-vapor temperature..Supercritical carbon dioxide (scCO2) has the property of gas-liquid characteristic and good compatibility with water, meanwhile water and PVA can generate strong hydrogen bond, so this project aims to use scCO2 and water as the co-blowing agent to improve the solubility of scCO2 in PVA, and obtain better thermoplastic foaming processing and cellular structure; to study the interaction between scCO2,water and PVA, as well as the structure, the state and the phase change process of scCO2 and water under the fields such as the temperature, pressure and shear force; to study the nucleation, growth and adjustment of bubble, as well as the co-foaming mechanism; the extrusion foaming instrument fitting the co-blowing agent scCO2 and water will be established which can be used to prepare the microcellular biomedical PVA foam with uniform foam structure and good comprehensive properties and the halogen-free flame retardant PVA foam with intrinsic flame retardant characteristics. Besides, it will bring novel principles and new methods for preparation of PVA foam material through thermal processing with important theoretical and practical significance。