Synchronously enhanced thermal conductivity and heat resistance in poly(l-lactide)/graphene nanoplatelets composites via constructing stereocomplex crystallites at interface
The wide application of the biodegradable polymers is the developing direction of the next generation microelectronic devices and electronic packaging because it can greatly reduce the risk of plastic pollution. However, most of biodegradable polymers have low thermal conductivity and low heat resistance. Synchronously improving the thermal conductivity and heat resistance of the biodegradable polymers without sacrificing the other performances is still great challenging. In this work, a novel method was proposed to highly efficiently improve the thermal properties of the poly(l-lactic acid) (PLLA) composites. To achieve this goal, hydroxylated graphene nanoplatelets were obtained by wet ball milling technology, and then ring-opening polymerization of lactide was initiated, and poly(d-lactic acid) (PDLA) and PLLA molecular chains were grafted on the hydroxylated graphene nanoplatelets to obtain the PDLA-graft-graphene nanoplatelets (G-g-PDLA) and PLLA-graft-graphene nanoplatelets (G-g-PLLA), respectively. Finally, the PLLA/G-g-PDLA and PLLA/G-g-PLLA composites were fabricated through melt compounding processing. The results showed that the PDLA molecular chains on the graphene nanoplatelets promoted the formation of the stereocomplex crystallites at the interface. Compared with the pure PLLA and PLLA/G-g-PLLA composites, the PLLA/G-g-PDLA composites exhibited higher thermal conductivity, largely enhanced heat distortion temperature, and better mechanical properties at high environmental temperature. For example, at G-g-PDLA content of 5 wt %, the composite sample showed the thermal conductivity of 1.12 W m?1K?1 and heat distortion temperature of 200 °C, which were 387 % and 65 °C higher than those of the pure PLLA, respectively. Morphological and microstructural characterizations were carried out and the mechanisms based on SCs formation at the interface were proposed. This work lights up the route for the application of the PLLA in the next generation microelectronic devices.
Publication date: 01/11/2021
Author: Ting Gu, De-xiang Sun, Xiao-dong Qi, Jing-hui Yang, Cheng-shou Zhao, Yan-zhou Lei, Yong Wang
Composites Part B: Engineering