Thermal transport in ultra-drawn polyethylene films

Mechanical stretching is an effective strategy for enhancing in-plane heat transport in polymers, yet the atomistic mechanisms governing thermal conductivity evolution under high draw ratios remain unclear. Here, thermal property measurements are combined with molecular dynamics (MD) simulations to elucidate the stretching-induced structural and heat transport evolution of polyethylene under different draw ratios. Experiments show a monotonic increase in in-plane thermal conductivity and thermal diffusivity with increasing draw ratio, providing macroscopic benchmarks. MD simulations reproduce the full deformation sequence from amorphous chain alignment to strain-induced crystallization and cavitation. Analysis based on an orientation order parameter reveals a direct correlation between tensile strain and crystallinity. In addition to crystalline domains, highly oriented interlamellar regions contribute substantially to the overall thermal conductivity. These results establish a mechanistic link between chain dynamics, phase evolution, and stretch-enhanced thermal transport in polymers.