Effect of Fillers on the Adhesion Properties of the Cured Unsaturated Polyester Adhesive

Abstract

Unsaturated polyester (UP) composed of maleic anhydride, phthalic anhydride and 1,2- propylene glycol has been prepared as an adhesive base component. Fillers are widely used in order to reduce cost and to control shrinkage in adhesive formulations. Four types of fillers of the same particle size (50 mesh) and different chemical properties, silica, alumina, talc, and kaolinwere used. The fillers were mixed with the unsaturated polyesterprepolymer in various contents (5, 10, 20, 30 and 40) part per hundred parts of resin (phr). Their effects on different adhesion properties have been investigated. Experimental results show, in general, that, the adhesion strength of the unsaturated polyester adhesive measured by the standard lap- shear test method (ASTM D-1002) was increased in accordance with the increase of the weight percentage of the loaded filler. Best results as an adhesion strength were obtained with the kaolin filler. In general, the effects provided by fillers are more dependent on the weight percent incorporated rather than the type. The more common fillers in use today are silica, talc, alumina and clays. It was found that the failure strength of the adhesive increased in accordance with the increase of the weight percentage of the filler to a certain limit. As a rule of thumb, no more than 30% of the entire mixture should be filler, or properties will be reduced.