Technique for Controlled Radical Polymerization in Curing Process of Acrylic Adhesive Containing Trialkyl Borane

Abstract

Acrylic Adhesives composed of trialkyl borane (R₃B) complex are used to adhere to difficult-to-bond surfaces of adherends such as polyolefins. The main factor of high adhesive strength is thought that the polymer grafting from the substrate surface of the adherend contributes to the improvement of the interfacial adhesive strength. To improve the share strength and to extend the working time, other method that halogenated metals (MX_n) are added to the adhesives has been proposed and has been already an important technique to acrylic adhesives compound of R₃B complex or partially oxidated R₃B. In this research, we investigate the effect of MX_n on the adhesion in detail and uncover that chain transfer agents (CTA) with thiocarbonyl groups have same effect as MX_n. The reason of this effect is assumed that MX_n or CTA reacts with propagating radical to give dormant species and the deactivation of propagating radical including terminating step and trapping by oxygen could be suppressed.