Mechanism of adhesion promotion between aluminium sheet and polypropylene with maleic anhydride-grafted polypropylene by γ-aminopropyltriethoxy silane

Abstract

The effect of concentration of γ-aminopropyltriethoxy (γ-APS) solution on shear strength of adhesive bonding between aluminium sheet and polypropylene (PP) with addition of a certain amount of maleic anhydride-grafted polypropylene (PP-g-MAH) has been investigated. It is shown that the lap shear strength is promoted obviously with pre-treatment of aluminium sheet by γ-APS. The maximum strength is obtained at a concentration of 3% γ-APS solution. With further high concentration of γ-APS, the lap shear strength decreases. The examination of the separated surfaces by X-ray photoelectron spectroscopy (XPS) shows that (C=O)2-O-Al and C(=O)-O-Al are formed for adhesive bonding between PP with the addition of 20 wt% PP-g-MAH and aluminium sheet without pre-treatment by γ-APS, and that the area ratio of C related to oxygen on the separated aluminium side is 33.28%, which is obviously higher than 14% on the polymer side. As for adhesive bonding between PP with the addition of 20% PP-g-MAH and 3% γ-APS pre-treated aluminium sheet, C(=O)-N-C(=O) and C(=O)-NH are formed. The area ratio of C related to oxygen on the separated polymer side increases to 24.99%. It is proposed that γ-APS pre-treatment improves the distribution and shape of PP-g-MAH chains in the region adsorbed on the substrate and the region adjacent to this region. The chemical interactions at the interface are also proposed. Copyright © 2008 John Wiley & Sons, Ltd.