Transcrystallinity in brominated UHMWPE fiber reinforced HDPE composites: morphology and dielectric properties

Ultra-high-molecular-weight polyethylene (UHMWPE) fibers were treated by photochemical bromination. The analysis of the fibers by XPS and ATR-FTIR showed that this process led to the introduction of C–Br and C–OH moieties and generated CC bonds at the PE fiber surface. ites were fabricated using either treated or untreated fibers and high-density polyethylene (HDPE) for the matrix. WAXD analysis showed that the treated fibers, through offering a higher concentration of crystallization nuclei, generated a denser transcrystalline layer with higher specific radial orientation with respect to the fiber axis—compared with the untreated fiber. Furthermore, the introduction of polarity onto the fiber surface enabled analysis of the complex relaxation behavior of PE/PE composites by dielectric spectroscopy. It showed the typical α, β and γ-relaxation processes of polyethylene, combined with the effect of the transcrystalline layer, generating—among other changes—a strong β-transition.