Annealing behavior of ultrahigh molecular weight polyethylene investigated by confocal micro-Raman spectroscopy combined with two-dimensional correlation spectroscopy

Annealing was performed for ultrahigh molecular weight polyethylene (UHMWPE), including an isothermal process at 110.0°C and cooling process from 110.0 to 30.0°C. The processes were in situ investigated by confocal micro-Raman spectroscopy combined with two-dimensional correlation spectroscopy. Two phase transitions were directly observed in the annealing processes, i.e., from the amorphous phase to the intermediate phase and from the intermediate phase to the crystalline phase. The phase transitions derive from molecular chain segments sliding between different phases of UHMWPE and occur in different orders during the isothermal and cooling processes.