UHMWPE fiber surface modification by atomic layer deposition of alumina

Ultrahigh molecular weight polyethylene (UHMWPE) fibers are highly crystalline fibers with superior mechanical properties and very high tensile strength. However, due to the fibers' non polar nature it is hard to bond them to other polymers. In this research, the fiber surface was modified using atomic layer deposition (ALD) of alumina at low temperatures. The surface treatment was aimed at increasing the adhesion between the fibers and an epoxy matrix without degrading the fiber mechanical properties (as often happens after fiber surface treatment). The Microbond technique was used to quantify the interfacial shear strength between the UHMWPE fibers and the epoxy matrix and it was found to be tripled compared to a non-treated fiber, without reducing the fibers' ultimate tensile strength. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to characterize chemical composition and surface morphology of the deposited layer. Young modulus and nano-hardness were derived from the nano-indentation measurements using an AFM probe. Nano-indentation results showed an order of magnitude increase in the fibers' Young modulus and nano-hardness after alumina deposition.