Fabrication of low-density poly(lactic acid) microcellular foam by self-assembly crystallization nucleating agent

Abstract

In this study, branched PLLA was obtained by mixing linear PLLA with chain extender. And adding different contents of self - assembled nucleating agent to further modify its crystallization properties. The crystallization and rheological properties were tested by POM, DSC and rheometer. It is proved that TMC- 300 was an effective crystallization nucleating agent for branched PLLA, self- assembled fiber could provide large number of crystallization nucleation sites to improve the crystallinity. The appropriate content of TMC- 300 can be self- assembled into fiber network framework to regulate the crystallization behavior of branched PLLA, and to increase storage modulus step by step. It can improve the melt strength of branched PLLA for low- density microcellular foaming at high temperature. The increase in the number of crystallization region and formation of self- assembly network framework can not only provide large number of cell nucleation sites, but also limit the growth of PLLA cells. And low- density microcellular foam with crystallinity of 36.5% was prepared by further synergistic interaction between TMC fiber framework and induced PLLA crystal. Compared with pure branched PLLA, the density of PLLA microcellular foams added with 1wt% TMC is increased by two orders of magnitude, the cell size is reduced to 10 μμm, and the foaming expansion ratio is up to ten- fold at 130 ℃.