The effect of incompletely condensed polyhedral oligomeric silsesquioxanes (POSS) on hybrid film adhesion

Abstract

The objective of this study was to investigate the influence of polyhedral oligomeric silsesquioxane (POSS) structure on the adhesion behaviour of composite films onto a metallic surface. The composite films consisted of UV cured bisphenol A glycidylmethacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) as matrix and reactive POSS structures as adhesion enhancers. Composites were made with 1, 3 and 5 wt % of POSS. Adhesion was evaluated using the micro Vickers hardness testing method. The contact angle of composite films to a brass substrate was measured and compared to the adhesion parameter obtained from microhardness measurements. Optical microscopy indicated morphological segregation in the hybrid films suggesting the compatibility extent between the matrix and each particle. The shape and size of the indent were analyzed and correlated with adhesion quality. The methods used for the estimation of adhesion strength and quality clearly indicated that the highest adhesion enhancement of the Bis-GMA/TEGDMA matrix was POSS reagent containing both polar (hydroxyl) and nonpolar (unsaturated aliphatic - allyl) side groups.