Effect of Atmospheric Pressure Nonequilibrium Plasma Pretreatment of Polyethylene/Polypropylene on Epoxy Adhesively Bonded Joints

ABSTRACT Effects of atmospheric‐pressure nonequilibrium plasma pretreatment of polyethylene (PE) and polypropylene (PP) on epoxy adhesively bonded joints have been investigated. The atmospheric‐pressure plasma sustained by RF power (RF plasma) and high‐voltage DC pulses (LF plasma) have been used to pretreat PP and PE surfaces. The tensile shear stress of epoxy‐bonded joints between cold‐rolled high‐tensile‐strength steel (SPFC980Y) and PE or PP pretreated with RF and LF plasma exhibited significantly higher values than those of the untreated counterparts. The results for SPFC980Y‐PP joints were greater for LF plasma treatment than for RF plasma treatment. The loss in bonding strength observed with RF plasma treatment was attributed to the thermal degradation of PP caused by the heat flux from the plasma.