Fabrication and Structure–Property Relationship of High-Strength UHMWPE Films with Enhanced Thermal Conductivity

Abstract Ultrahigh molecular weight polyethylene (UHMWPE) shows great application potential in flexible electronic thermal management and lightweight protection due to its low density, superior specific strength, and excellent electrical insulation. However, previous studies mainly focus on independently optimizing the mechanical or thermal conductivity (TC) of UHMWPE films, while the underlying mechanism of simultaneous regulation of both properties via crystalline structures remains unclear. In this work, shish crystals were retained during UHMWPE dissolution to enable sufficient chain disentanglement. Combined with multistage hot drawing, a strongly oriented crystalline structure was constructed to fabricate mechanically strong UHMWPE films with enhanced TC. The synergistic regulation mechanism of crystal evolution during ultradrawing on mechanical and thermal transport properties was systematically investigated. Increasing the draw ratio (DR) extends and orients molecular chains in densely entangled amorphous regions, promoting abundant short, small-diameter new shish crystals and improving the regularity of retained shish crystals. The concurrent rise in shish crystal orientation and total content optimizes both stress transfer efficiency and phonon transport pathways. At a DR of 48.5, the film achieves an in-plane TC of 42.1 W m–1 K–1 at 25 °C and a tensile strength of 1.49 GPa. This work provides new insights for the industrial preparation of advanced-performance flexible UHMWPE films.