Combination effects of reinforcing filler and impact modifier on the crystallization and toughening performances of poly(lactic acid)

In this research, poly(lactic acid) (PLA) was toughened and improved the crystallinity by rubber particles and inorganic filler. CaCO3 was employed as a filler and nucleating agent while poly(methyl methacrylate)-poly(butadiene-styrene) (MBS) core-shell impact modifier was added as a toughening agent. Overall, the enhancements of both the toughness and crystallization of PLA with CaCO3 and MBS were successfully achieved. The tensile modulus and strength of PLA increased with increasing CaCO3 content from 10 to 30wt%. However, they decreased slightly when CaCO3 loading reached 40 wt% due to particles agglomerations. With the addition of MBS rubber, the tensile modulus and strength of the PLA/CaCO3 composites became lower than those observed for PLA/CaCO3 composites due to the softening effect. Furthermore, the compositions with MBS showed superior toughness in terms of the tensile elongation at break and impact strength. CaCO3 nucleated the PLA crystal which reflected as the increase in the degree of crystallinity (X-c) by at least 2 times for all formulations studied. The crystallization half-time (t(1/2)) of PLA with 40 wt% CaCO3 was dramatically reduced, from 26 min, in neat PLA, to 0.9 min. With the addition of MBS, it did at 2.7 min for the same CaCO3 content. The maximum increment of heat distortion temperature (HDT), around 8 degrees C, was found for the PLA with 20 wt% CaCO3.