A synergy of atmospheric plasma and UV-additive incorporated PU and styrene–isoprene-styrene adhesive for improving inter-layer adhesion in PVF/Fabric/BOPET laminate for aerostat envelope

Abstract

Engineers and material scientists face a significant challenge in finding the right adhesive and technology to join the layers of a multi-layered laminated composite for making lightweight aircrafts. This paper focuses on a novel method of exposing substrates to atmospheric-plasma using different purging gases and subsequent adhesive-lamination. Three separate plasma-exposed layers— polyvinyl fluoride (PVF) film, polyester fabric, and biaxially oriented polyethylene terephthalate (BOPET) film were joined together using two different solvent-borne/pressure-sensitive adhesives, based on polyurethane and styrene-isoprene-styrene. Both adhesives were compounded with organic UV-additives and nano-carbon black for improving weather resistance. The composite laminates were exposed to accelerated weathering for 100h to qualify for the targeted application of aerostat envelope/hull. Among different gas combinations, the helium/oxygen-mixture (80:20) showed the best results in terms of surface etching/functionalization, which strongly attributed to improving adhesion-strength. Among two adhesives, styrene-isoprene-styrene-based adhesive performed much better. This adhesive was UV-cured after post-weathering cycle, and it improved inter-laminar adhesion strength by 81% and reached 16.2 N/cm. As a consequence, it prevented adhesive breakage from the weak bond layers and turned it into a cohesive failure from the adhesive layer. Most importantly, the laminated fabric showed excellent helium gas barrier property, which improved further after weathering cycle, making it ideal for the targeted application.