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.