聚合物共混体系连续挤出发泡双峰泡孔结构的调控和机理研究

Polymer foams with bimodal cell structures have showed new prospects in wide applications due to their excellent properties. They are defined as foams composed of large and small cells, with the small ones of 5-50% in size of the big ones. As it is still a challenge to prepare and control bimodal cell structures in polymer blends via continuous extrusion, the classical foamable polymer blends of polypropylene/polystyrene (PP/PS, nonpolar/nonpolar) and polystyrene/polymethylmethacrylate (PS/PMMA, nonpolar/polar) are used in this study to work on this issue in continuous extrusion foaming with supercritical fluids as the foaming agent. First, the cell nucleation in PP phase and PS phase (or PS phase and PMMA phase) will be controlled via adjusting the volume of supercritical CO2 and by the selective distribution of nanoparticles (type, polar and nonpolar, processing means, content) in the polymer blends to study the effect of the difference in cell nucleation ability in the two phases on the cell structures. Second, the phase morphologies of the polymer blends will be controlled by the plasticization of polymers with supercritical CO2 during processing, and the effect of the blend ratio, the phase morphologies and the interphase will be discussed on the cell structures. Based on this study, it will establish the relationship between the cell nucleation difference in two phases in the polymer blends and the formation of bimodal cell structures as well as the relationship between the phase morphologies of the blends and the corresponding bimodal cell distribution. Thereby, it is expected to propose the formation mechanism and build the methodology for controlling and predicting the tunable bimodal cell structures. In addition, it would provide advances and insights in theoretical supports for preparing bimodal cell structures in polymer blends.

聚合物双峰泡孔发泡材料性能优异具有广阔的应用前景，其被定义为小孔尺寸为大孔尺寸5-50%的泡沫材料。针对连续挤出发泡聚合物共混体系如何制备和有效调控双峰泡孔的问题，本项目选用经典发泡体系聚丙烯/聚苯乙烯（PP/PS，非极性/非极性）和聚苯乙烯/聚甲基丙烯酸甲酯（PS/PMMA，非极性/极性）共混物为研究对象，采用超临界流体连续挤出发泡，一方面通过加工过程中二氧化碳气量和纳米填料（种类、极性和非极性、添加方式、添加量）的选择性分散控制两相的成核密度，探索两相成核能力的差异对泡孔结构的影响，另一方面通过加工过程中超临界流体对聚合物的塑化作用控制相形态，探索组成、相形态、相界面对泡孔结构的影响。在此基础上，阐明两相成核密度差异与双峰泡孔形成的关系及相形态与双峰泡孔分布的关系。本项目预期揭示聚合物共混体系连续挤出发泡双峰泡孔结构的调控机理和方法，为聚合物共混体系双峰泡孔结构的制备提供理论指导。

本项目针对聚合物共混体系连续挤出发泡如何制备及有效调控双峰泡孔结构的问题，选用经典发泡体系聚丙烯/聚苯乙烯（PP/PS）和聚苯乙烯/聚甲基丙烯酸甲酯（PS/PMMA）共混物为研究对象，一方面采用超临界流体连续挤出发泡技术，通过控制加工过程中二氧化碳气量和挤出口模压力及添加纳米填料控制两相的成核密度，探索两相成核能力的差异与泡孔结构的关系，另一方面通过加工过程控制共混体系的相形态，探索组成、相形态、相界面对泡孔结构的影响规律。本项目揭示了聚合物共混体系两相成核密度差异与双峰泡孔形成的关系，构建了相形态与发泡行为、泡孔结构及发泡温度窗口的关系。本项目最终阐明了聚合物共混体系双峰泡孔结构的调控机理和方法，为聚合物共混体系双峰泡孔的制备提供理论指导，并揭示了两相粘弹性差异对发泡窗口的决定作用。