In‐situ exfoliation and thermal conductivity in phase‐transition‐assisted melt blending fabrication of low‐density polyethylene/expanded graphite nanocomposite

Abstract Expanded graphite (EG) exhibits excellent thermal property, high specific surface area, and large aspect ratio, which show promise for fabricating polymer composites with high thermal conductivity. However, the wormlike structure of EG makes it difficult to be exfoliated and dispersed in polymer matrix. To meet this challenge, herein, a one‐step melt mixing strategy based on the phase‐transition‐assisted in‐situ exfoliation is developed to fabricate EG‐low density polyethylene composites with high thermal conductivity. SEM images and WAXD analyses showed that the internal force generated by phase transition makes EG to be quickly exfoliated and dispersed in melts within 8 min. POM images and DSC results suggested that the exfoliated EG can introduce heterogeneous nucleation to LDPE macromolecules and improve the crystallinity of composites. Moreover, the EG‐LDPE composites prepared by this strategy have a thermal conductivity of 0.715 Wm −1 K −1 with the loading of 5 wt. % EG. This value exceeds the composites prepared by regular melt mixing, achieving the enhancement efficiency of graphene nanoplatelets (GNP). This strategy has great potential in preparing polymer composites with high thermal conductivity.