| The purpose of the research has been to understand plasma-substrate interactions and an application to adhesion enhancement of high performance fiber under capacitively-coupled atmospheric pressure plasma. Preliminarily, plasma-poly(ethylene terephthalate) (PET) film interactions with atmospheric pressure capacitively-coupled plasma were studied under closed-ventilation conditions with exposure times of 0–5 min., using He/Air and He/O2 gases. The weight loss (%) increased initially and then decreased at further exposure times in both gas plasma treatments. Contact angle measurements showed that wettability increased rapidly up to 1 min. and was constant at further exposure times. Atomic Force Microscopy (AFM) was used to characterize the surface morphology change of the PET films. Surface functionalization and cross-linking were examined by X-ray Photoelectron Spectroscopy (XPS). Both plasma treatments induced functionalization after chain-scission, and generated etched particles, a potential source for re-deposition. Re-deposition effects on weight loss (%), roughness, carbon content and surface functionality increased with plasma exposure time. Cross-linking was dependent on plasma exposure time and also on helium content. Tensile strength and initial modulus of PET films increased after treatments in both gas plasmas. The contribution of helium was a major factor increasing cross-linking.; In order to investigate the effect of atmospheric pressure plasmas on adhesion between aramid fibers and epoxy, aramid fibers were treated with atmospheric pressure helium/air for 15, 30 and 60 seconds on a capacitively-coupled device at a frequency of 5.0 kHz and He outlet pressure of 3.43kPa. SEM analysis at 10,000× magnification showed that no significant surface morphological change resulted from the plasma treatments. XPS analysis showed a decrease in carbon content and an increase in oxygen content. Deconvolution analysis of C1s, N1s and O1s peaks showed an increase in surface hydroxyl groups that can interact with epoxy resin. The microbond test showed that the plasma treatment for 60 seconds increased interfacial shear strength by 109% over that of the control (untreated). The atmospheric pressure plasma increased single fiber tensile strength by 16–26%. |
