METHOD FOR IMPROVING FOAMING RATE OF POLYLACTIC ACID THROUGH PRE-ISOTHERMAL COLD CRYSTALLIZATION TREATMENT

摘要

The present invention relates to a method for improving the foaming rate of polylactic acid through pre-isothermal cold crystallization treatment. The method comprises the following steps: 1) preparing polylactic acid or a blend thereof into an amorphous or low-crystalline blank through melt-extruding or hot-pressing; 2) performing pre-isothermal cold crystallization treatment on the blank to obtain a pre-isothermal treated specimen with a certain crystallinity degree and crystallization morphology; and 3) performing high-pressure gas swelling and penetrating on the pre-isothermal treated specimen, and depressurizing same quickly to prepare a foam material. By the present invention, the difficult technical problems that semi-crystalline polylactic acid melt is low in strength, poor in foamability and low in foaming rate can be effectively solved; the cellular structure of a polylactic acid foaming material can be regulated and controlled; moreover, the process is simple, the procedure is green, and the cost is low; and the application field of the polylactic acid foaming material can be further expanded.