PLASMA-TREATED ULTRA-HIGH-STRENGTH POLYETHYLENE FIBERS IMPROVED FRACTURE-TOUGHNESS OF POLY(METHYL METHACRYLATE)

Use of ultra-high-strength polyethylene (UHSPE) fibres in composites has been limited by problems with adhesion to the matrix. The present study presents a gas-plasma treatment of UHSPE staple fibres (Spectra 900 and 1000) to improve adhesion to poly(methyl methacrylate). The gases used were nitrogen, argon and carbon dioxide for treatment times of 0 and 1 min. No significant differences were observed in flexural stresses, and only modest improvements were seen in the flexural modulus and the stress-intensity factor by reinforcing the cements with surface-modified UHSPE fibres. At least a sixfold improvement in the toughness index (fracture energy) was observed by reinforcing the cements with carbon dioxide treated fibres with a fibre index, l/d, of 776 at 1 wt %. The fibres added reinforcement by a crack-bridging effect that significantly improved the toughness index. The plasma treatment altered the fibre surface sufficiently to cause significant differences in the susceptibility to plastic flow during the fibre pull-out process.