Enhancement of Wetting and Mechanical Properties of UHMWPE-Based Composites through Alumina Atomic Layer Deposition

Ultrahigh molecular weight polyethylene (UHMWPE) fibers suffer from poor adhesion to polar matrices in composites due to their chemically inert surface, thus limiting the use of UHMWPE-based fabrics and composites. Atomic layer deposition (ALD) is a useful method of constructing a thin oxide layer, with a variety of oxides available, enabling a nondestructive method for surface modification. Here, UHMWPE fibers and fabrics are coated by ALD with a thin alumina layer, using two precursors—trimethylaluminum (TMA) and water—to a final coating thickness of 39 nm. The effect of the oxide coating layer is determined by various mechanical and physical tests. The contact angle is reduced by 44–49%, indicating a substantial increase in wettability. Significant improvements are observed in the flexural modulus, flexural strength, interlaminar shear strength, resilience, and toughness. Frequency dependence tests show an improvement in storage modulus at all tested frequencies, insinuating higher impact toughness at high strain rates. Failure analysis reveals a change in the failure mode, from pinholes formation and adhesion failure to cohesion failure and mixed failure modes. Thus, the use of ALD alumina-coated UHMWPE fibers in composites shows high scientific and technological potential.