Effect of silane treatment parameters on the silane layer formation and bonding to thermoplastic urethane

Enhancing adhesion is of primary importance in preparation of insert injection molded plastic–metal hybrids. Here, the combination of coupling agent application parameters and steel oxide microstructure effects on the adhesion in thermoplastic urethane–stainless steel hybrids was studied. The stainless steel oxide structure was first modified by electrolytical polishing and subsequent oxidation treatment, then the steel was coated with N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (γ-AEAPS) prior to overmolding with thermoplastic urethane. The properties of formed silane coatings and ultimately the thermoplastic urethane–stainless steel hybrids were determined by several microscopical methods, infrared spectroscopy and mechanical testing. The bond strength of hybrids depended on the silane layer thickness. Also the stainless steel surface oxide structure had a remarkable influence on the coating formation and the resulting hybrid bond strength.

► Stainless steel oxide structure affected the aminosilane coating formation.
► The oxidation treatments of substrates increased the peel strength of the hybrids.
► Silane layer thickness on oxidized steel depended on silane bath concentration.
► The coating thickness and hybrid peel strength correlated up to 20 nm.