Durable bonding characteristics of thermoplastic olefins plasma-treated by low-temperature cascade arc torches

Abstract

Low-temperature cascade arc torch (LTCAT) polymerization was applied to modify surface characteristics of thermoplastic olefins (TPOs). LTCAT has a unique feature that the activation of carrier gas (Ar) via creation of a plasma state and the deactivation of excited species that lead to surface modification or to the deposition of plasma polymer are spatially de-coupled. Consequently, the addition of a monomer or a reaction gas in the reaction chamber does not influence the first step of Ar plasma formation. The main active species in LTCAT are excited Ar neutrals, and no electric field exists in the reaction chamber. It was found that the beams of excited Ar neutrals are ideally suited for the surface modification of polymers because undesirable damage caused by the bombardment of energetic species can be avoided. The LTCAT of Ar was found to yield stable modification of TPO surfaces via post-plasma reaction of the treated surface with ambient oxygen. An excellent adhesion of a primer coating to surface of TPOs was obtained by treatment of the surface with Ar LTCAT, which passed the tape test after scribed samples were boiled in water for 8 h.