Supporting information from High density polyethylene crystals with double melting peaks induced by ultra-high molecular weight polyethylene fibre

High density polyethylene (HDPE)/ultra-high molecular weight polyethylene (UHMWPE) fibre composite as an example were prepared via solution crystallization to investigate the components of crystals growth epitaxially on highly oriented substrate. Scanning electron microscopy (SEM) morphologies of HDPE crystals on UHMWPE fibres revealed that edge-on ribbon pattern crystals formed initially on UHMWPE fibres converted afterwards to sheet shape as crystallization time goes on. Wide-angle X-ray diffraction (WAXD) uncovered that the polymer chain oriented along fibre axis and orthorhombic crystal form of HDPE remained unchanged in HDPE/UHMWPE fibre composite systems. Thermal behaviour of fibre composites measured by differential scanning calorimetry (DSC) showed double melting peaks, the nature of which disclosed by partial melting experiments is ascribed to bilayer components existing in the induced crystals: inner layer is composed of more regularly folded chain crystals induced by UHMWPE fibre; outer layer formed on the inner one with thinner and lower ordered crystal structure.