Crystal and Thermal Properties of PLLA/PDLA Blends Synthesized by Direct Melt Polycondensation |
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| Authors: | Dakai Chen Jing Li Jie Ren |
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| Institution: | (1) Institute of Nano- and Bio-Polymeric Materials, School of Material Science and Engineering, Tongji University, 200092 Shanghai, China;(2) Key Laboratory of Advanced Civil Engineering Materials, Ministry of Education, Tongji University, 200092 Shanghai, China; |
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| Abstract: | We herein report the effects of the component ratio and method of blending on the synthesis of stereocomplex poly(lactic acid)
(SC-PLA) based on poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) prepolymers. PLLA and PDLA were prepared by direct melt polycondensation of lactic acid (DMP). Combined
with the dual catalyst system, PLA prepolymers with Mw more than 20,000 were prepared by DMP. PLLA was mixed by powder blending or melt blended with PDLA. It is revealed that melt-point
and spherulite growth rate of SC-PLA is strongly dependent on the perfection of SC structure. The melt point of PLA can be
increased by nearly 50 °C because of the particular strong intermolecular interaction between PLLA and PDLA chains. Solid-state
polycondensation (SSP) is an efficient method to increase the molecular weight of SC-PLA, but it can have a negative effect
on the regularity of linear chains of SC-PLA. Thermogravimetry analyzer (TGA) results show that SC structure cannot cause
the delay reaction on the thermal degradation of PLA. |
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