Preparation and thermal conductivity of flexible phase change composite materials with oriented thermal conductivity structure

To address the issue of poor inherent thermal conductivity in polymer-based composites, this study employed a simple, efficient, and industrially viable kneading method to construct an ordered orientation structure within a polyolefin elastomer (POE) matrix, resulting in a flexible phase-change composite material with outstanding comprehensive performance. Under the strong shear field of the kneader, paraffin wax (PW) and boron nitride (BN) were oriented and arranged along the shear field direction within the POE matrix, facilitating the construction of thermal conduction pathways. When the graphene nanoplatelets (GNPs) and BN content were 2wt% and 25wt%, respectively, the thermal conductivity (λ) of the PW-2wt%GNPs-25wt%BN/POE phase-change composite material increased from 1.01 W·m⁻¹·K⁻¹ (PW/POE) to 2.59 W·m⁻¹·K⁻¹, representing a 156% enhancement. Moreover, the PW-2wt%GNPs-25wt%BN/POE phase-change composite material exhibited excellent tensile strength (18.3 MPa) and elongation at break (720%), with no signs of rupture after bending and folding into complex shapes, and demonstrated good recoverability in 10 cycles of tensile testing. Furthermore, adding 30wt% PW can endow PW-2wt%GNPs-25wt%BN/POE composite material with a certain enthalpy value of 44.1 J·g⁻¹. Under an illumination intensity of 80 mW cm⁻², the temperature inside a bottle coated with the PW-2wt%GNPs-25wt%BN/POE composite material reached 54.3°C, which was 20°C higher than that of the PW/POE without GNPs. Moreover, under illumination conditions, the PW-2wt%GNPs-25wt%BN/POE composite material exhibited excellent light-driven recoverable performance, suggesting its potential application in photothermal conversion, and thereby possessing significant potential for practical applications and industrial production.