Atmospheric Plasma Treatment of Nylon 6,6 for Improved Interfacial Adhesion in Thermoplastic Composites

The physio-chemical modifications of polyamide (Nylon 6,6) obtained from exposure to an atmospheric dielectric barrier discharge were examined. Specifically, the surface energy, surface chemical composition, and interfacial adhesive strength were studied using water contact angle goniometry, x-ray photoelectron spectroscopy, and single joint lap shear testing. Nylon substrates were plasma treated with both O₂ and water vapor (H₂O) in He for 30, 60, and 180 seconds, resulting in the functionalization of the surface via the addition of reactive chemical groups such as −OH that change the energy, composition, and reactivity of the surface. The studies revealed that He/H₂O plasma treatments were more effective at functionalizing the surface than He/O₂ plasma treatments, resulting in a more than 40% decrease in the water contact angle. XPS results show a significant increase in the amount of surface oxygen after treatment, and lap shear experiments show an almost ∼300% increase in interfacial adhesive strength.