CONTROLLED INTERFACES OF ULTRA-HIGH MODULUS POLYETHYLENE AND ARAMID FIBERS FOR ADVANCED COMPOSITES

High strength, high modulus organic fibres such as aramid and ultra-high modulus polyethylene (UHMPE) are attractive engineering materials for high-tech composites. In order to improve their inherently poor adhesion to the matrix resin, it is required to surface-modify these fibres by incorporating specific chemical groups onto their surfaces. A new surface engineering process, SICOR, developed by CSIRO allows for a simple and economically feasible incorporation of optional chemical functionalities onto the surfaces of polymers in any form, including fibres. The effectiveness of the process for the treatment of UHMPE and aramid fibres is assessed by examining the interlaminar fracture energy and flexural modulus as well as SEM analysis of the fracture surfaces of composites fabricated from the untreated, corona discharge treated, ammonia plasma treated and the amine grafted (using the novel SICOR process) UHMPE and aramid fabric. Significant improvement of interfacial adhesion is confirmed by increases in interlaminar fracture energies and flexural moduli. The effectiveness of the process investigated is similar to the ammonia plasma treatment. The SEM analysis of fracture surfaces indicates a change in the failure mode from purely adhesive for unmodified fibres, through to mixed failure mode for corona-treated material to highly cohesive-in-fibre failure for the SICOR-treated UHMPE fibres. XPS analysis confirms the incorporation of amine groups onto the surface of polyethylene treated using the novel method.