Rate-dependent phase transition of high density polyethylene

Abstract Quasi-static and dynamic tension tests are conducted on a widely used semicrystalline polymer, high density polyethylene (HDPE), to explore the strain rate effects on phase transition. HDPE exhibits considerable strain-rate hardening. In situ , high-speed x-ray diffraction demonstrates a martensitic transformation from the orthorhombic to monoclinic phase during both loading conditions. However, compared to quasi-static loading, the phase transition occurs at a lower bulk strain but higher stress under dynamic loading (strain rate 5100 s − 1 ), suggesting strain-rate-accelerated phase transition dynamics. Evolutions of lattice strain with bulk stress indicate different roles of amorphous and crystalline phases in deformation under different strain rates.