关键词: 超临界CO₂, 聚合物加工, 结晶, 发泡, 溶解, 扩散

Abstract: The use of CO₂ for substituting volatile organic compounds in polymer processing, i.e., supercritical CO₂-assisted polymer processing, has attracted increasing attention in recent years. Dissolution of CO₂ in polymer could swell, plasticize and deliver small molecules into the polymer matrixes. Consequently, the structure and morphology of the polymer would change, as well as the fundamental properties, including polymer crystallization, interfacial tension between polymer and gas, and rheology of CO₂/polymers melt.CO₂-induced changes in these properties could be used to realize the supercritical CO₂-assisted polymer processing, e.g., CO₂-assisted polymer grafting, CO₂-assisted penetrating of small molecules into polymer and CO₂-assisted polymer foaming.Several cases from the authors' laboratory are presented for elucidating how to use the changes to manipulate the CO₂-assisted polymer processing.The cases include CO₂-induced crystallization of isotactic polypropylene and syndiotactic polypropylene, CO₂-induced crystal phase transition of isotactic poly-1-butene, and how to use CO₂-induced crystallization to manipulate melt strength of three linear polymers, i.e., isotactic polypropylene, poly(lactic acid)and poly(ethylene terephthalate), to prepare the polymer foams with different structures.

Key words: supercritical CO₂, polymer processing, crystallization, foam, solution, diffusion