Enhanced thermal conductivity of poly(lactic acid)/alumina composite by synergistic effect of tuning crystallization of poly(lactic acid) crystallization and filler content

Thermally conductive polymer-based composites have drawn significant interest in the field of heat management. Herein, taking polylactic acid/alumina (PLA/Al2O3) composite as the research system, we investigated the influences of the content of Al2O3 and the crystallinity of PLA on the thermal conductivity of PLA/Al2O3 composite, and discussed the synergistic effect between the matrix crystallinity and the filler content and the corresponding thermal conduction mechanism. Results show that Al2O3 plays a heterogeneous nucleation role in crystallization of PLA, which significantly accelerates the crystallization rate and improves the crystallinity of PLA. Both crystallinity of PLA matrix and Al2O3 content contribute to the final thermal conductivity of the composite. When the filler content is lower than 50 wt%, the improvement of thermal conductivity for composite is mainly determined by Al2O3 content, and contribution from the crystallinity of PLA is very limited. When the Al2O3 content is higher than 60 wt%, which is sufficient to format a heat conduction network in the matrix, the high crystallinity of PLA combined with high filler content brings a synergistic effect and significantly enhances the final thermal conductivity of the composite. For composite of PLA containing 70 wt% Al2O3, when the crystallinity of PLA matrix increases from 4.63 to 59.8%, the corresponding thermal conductivity of the PLA/Al2O3 composite enhanced by 26.8% from 0.82 to 1.04 W m(-1) K-1, which is more than 5 times higher than that of neat PLA. Such a remarkable improvement in thermal conductivity only by changing matrix structure without further adding fillers is of great significance for polymer-based thermally conductive composites.