Different states in orthorhombic crystalline phase of high-density polyethylene

Two-dimensional (2D) FT-IR spectroscopy along with high-resolution and cryogenic techniques was used to investigate the CH2 rocking bands (750–700cm−1) of high-density polyethylene (HDPE). The 2D asynchronous spectrum shows that multiple forms of orthorhombic polyethylene co-exist in HDPE. Each of the two orthorhombic bands around 730 and 720cm−1, is composed of at least two sub-bands. The differences in peak position for the sub-bands are less than 1cm−1. The co-existence of multiple orthorhombic polyethylene may be helpful in understanding the variation of the peak positions, bandwidths and relative intensities of the orthorhombic polyethylene bands of polyethylene.