Aging of surface properties of ultra high modulus polyethylene fibers treated with He/O2 atmospheric pressure plasma jet

To investigate the relationship between aging of the treatment effect and the gas composition of atmospheric pressure plasma treatment, ultra high modulus polyethylene (UHMPE) fibers were selected as a model fiber to study the aging behavior of fiber surface treated by atmospheric pressure plasma jet (APPJ) with pure helium, helium + 1% oxygen, and helium + 2% oxygen. Atomic force microscopy showed increased surface roughness, while X-ray photoelectron spectroscopy revealed increased oxygen contents after the plasma treatments. The plasma treated fibers had lower contact angles and higher interfacial shear strengths to epoxy than those of the control fiber. Adding 1% of O2 to helium increased effectiveness of the plasma in polymer surface modification and suppressed aging after the treatment, while adding 2% of O2 had a negative effect on the APPJ modification results and accelerated aging. In addition, no significant difference in single fiber tensile strength was observed between the control and the plasma treated fibers.