Abstract: The physical foaming technology of supercritical fluid foaming and chemical foaming technology were combined to fabricate porous structure for polymers. Sodium bicarbonate was used as a chemical foaming agent. Poly(ε-caprolactone) (PCL) was first blended with sodium bicarbonate by a twin screw extruder and pelletized. The different foaming processes were conducted on a conventional injection molding machine and a microcellular injection molding machine separately. The foaming results were investigated by comparing the two methods of injection molding and microcellular injection molding. The results revealed that it was feasible by combining physical foaming and chemical foaming to fabricate porous structure for PCL, whose foaming quality was better than that of only chemical foaming method. The introduction of chemical foaming agent not only improved general foaming, but also served as nucleating agent of the gas bubbles of physical foaming. The interconnectivity of the pores was investigated, as well as the "web" structure on the cell walls. When the bubbles were growing, the cell walls were stretched in different directions, and the mutual wall of neighbored pores was stretched by the pores, therefore the "web" structure was obtained.

Key words: poly(ε-caprolactone), supercritical fluid, carbon dioxide, sodium bicarbonate, foaming, nucleation, porous structure

摘要： 将超临界气体发泡技术与化学发泡技术联合用于制备多孔材料。采用碳酸氢钠作为化学发泡剂，将聚己内酯与碳酸氢钠挤出共混之后，使用传统注射成型和微注射成型，进行了发泡实验对比。结果表明，物理化学联合发泡用于制备多孔材料具有可行性，化学发泡剂的加入不仅改善了整体发泡效果，还能够作为气泡成核剂促进物理发泡的质量。对于所得结构在一定程度上表现的泡孔相互连通性进行了讨论，同时对泡孔壁面上出现的“网”状结构进行了分析。气泡在成核生长过程中，对于泡孔壁产生多方向拉伸的作用，相邻气泡共同作用于公共壁面，最终导致壁面部分形成“网”状结构。

关键词: 聚己内酯, 超临界流体, 二氧化碳, 碳酸氢钠, 发泡, 成核, 多孔状结构