Surface modification of aluminum foil and PTFE film by graft polymerization for adhesion enhancement

Abstract

Modification of aluminum foils via surface graft polymerization of glycidyl methacrylate (GMA) to promote their adhesion to the similarly modified poly(tetrafluoroethylene) (PTFE) films is reported. The properly cleaned surface of the aluminum foil was first silanized with 3-(trimethoxysilyl)-propyl-methacrylate (APS). The silanized Al foil was pretreated with Ar plasma to generate peroxides and hydroperoxides before been subjected to UV-induced graft polymerization of GMA (the Al-APS-g-GMA surface). The Ar plasma-pretreated PTFE film was similarly modified by UV-induced graft copolymerization with GMA (the GMA-g-PTFE surface). The modified aluminum and PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. The adhesion between the Al foil and the PTFE film was achieved by introducing a small amount of GMA and hexamethylenediamine (HMDA) solution mixture or HMDA alone at the lapped interface, followed by curing at elevated temperature. T-peel adhesion strength of ~13 N cm-1 was achieved for the Al-APS-g-GMA/GMA + HMDA/GMA-g-PTFE assembly, compared to only ~5 N cm-1 attainable in the corresponding Al/GMA + HMDA/GMA-g-PTFE assembly involving only the pristine Al foil. Similarly, the use of GMA graft-copolymerizied PTFE film resulted in a significant increase in adhesion strength of the Al/PTFE assembly over that obtained using only the plasma-treated PTFE film. Cohesive failure in the bulk of the PTFE substrate was observed for the Al-APS-g-GMA/GMA + HMDA/GMA-g-PTFE assembly. (C) 2001 Elsevier Science B.V.