Enhanced Thermal Conductivity and Mechanical Properties of HDPE / MWCNTs / CF Composites via the Synergy of Sequential Mixing and Elongational Stress

ABSTRACT The incorporation of thermally conductive fillers often deteriorates the mechanical performance of polymer composites due to fillers agglomeration and insufficient interfacial interaction. Motivated by this challenge, a processing strategy based on the synergy of sequential mixing and elongational stress was proposed. Specifically, multi‐walled carbon nanotubes (MWCNTs) were pre‐dispersed in an HDPE matrix under elongational stress prior to the introduction of carbon fiber (CF). The proposed processing strategy promoted the dispersion of fillers within the matrix and improved the effective retention length of CF. SEM observations revealed improved dispersion of fillers and enhanced interfacial interaction between CF and the HDPE matrix. As a result, the thermal conductivity of the HDPE/MWCNTs/CF composites reached 0.751 W/(m K), and the tensile strength and tensile modulus increased to 32.81 and 961.26 MPa, corresponding to enhancements of 51.41%, 32.94%, and 172.03% compared with the pristine HDPE under the same processing conditions. These results demonstrated that the synergy of sequential mixing and elongational stress effectively enhanced thermal transport efficiency while simultaneously preserving mechanical integrity in polymer composites.