Crystallization and Foaming Properties of High-melt-strength Poly (lactic acid)
ZHAO Zhongguo, ZHANG Xin, CHENG Shaohua, WANG Miao, LIANG Panxu, LI Wanshun, JIA Shikui
National and Local Engineering Laboratory for Slag Comprehensive Utilization and Environment Technology, School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723000, China
Abstract: In this paper, effects of the long-chain branched on the crystallization behavior, mechanical properties and foaming properties of linear PLA were studied in detail. Long-chain branched PLA (LCBPLA) was obtained by adding pentaerythritol triacrylate (PETA), dicumyl peroxide (DCP) and TETDS. In the torque rheometer, with the increase of PETA content, the mixing energy gradually increased, from 4.5 kJ to 7.25 kJ. The analyses of non-isothermal and isothermal crystallization show that the formation of the long-chain branched structure could significantly improve the crystallization performance of PLA. With the increase of PETA content (from 0% to 1%), the crystallinity of LCBPLA increased from about 3.5% to about 45%, the initial crystallization temperature increased from about 120 ℃ to about 143 ℃, and the crystallization rate also significantly increased. In addition, the formation of a long-chain branched structure also improved the mechanical properties of PLA to some extent, from 68.8 MPa to 82.7 MPa, because the long-chain branched structure can form a network structure. It was found that modified PLA had better foaming property by supercritical CO2 at different foaming temperatures. Compared with pure PLA, the foaming ratio and foam size of modified PLA were significantly increased. The foaming ratio of PLA was increased from 8.7 to 30.5 at 155 ℃.
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2020, Vol. 34 
