Atmospheric pressure helium plus oxygen plasma treatment of ultrahigh modulus polyethylene fibers

Ultrahigh modulus polyethylene fibers were treated with atmospheric pressure helium + oxygen plasma in a capacitively coupled device at a frequency of 7.5 kHz. The fibers were treated for 0, 0.5, 1, 1.5, and 2 min. The surfaces of the fibers treated with He + O-2 plasma were etched and micro-cracks were formed. XPS analysis showed a 65-213% increase in oxygen content on the surfaces of all plasma-treated fibers, except for the 1.5 min group. An increase in the concentration of C-O and the appearance of C=O bonds on the surfaces of plasma-treated fibers were observed. In the micro-bond test, He + O-2 plasma-treated groups had a 65-104% increase in interfacial shear strength over that of the control. The tensile strength of the fibers was either unchanged or decreased by 10-13% by the plasma treatments.