Dismantlable adhesion properties of reactive acrylic copolymers resulting from cross-linking and gas evolution

Abstract

ABSTRACTThe acrylic copolymers involving 2-hydroxyethyl acrylate (HEA) and tert-butyl acrylate (tBA) units as reactive units behave as pressure-sensitive adhesive type dismantlable adhesive materials. In order to clarify the individual role of HEA and tBA units on dismantlability, the 180° peel behavior after the dismantling treatment, i.e., heating in the presence of given amount of acid catalysts, was systematically investigated using the acrylic copolymers involving different amounts of the reactive units. It was revealed that transesterification of HEA units resulted in an increase in the cohesive force and modulus due to an increase in the molecular weight and cross-linking. Deprotection of tBA units, i.e., transformation of tBA to acrylic acid (AA) unit with isobutene evolution, promoted cross-linking by the esterification of AA units and tended to reduce a cohesive force by forming voids in the adhesive layer due to the evolution of isobutene gas. Interfacial failure in the peel tests corresponded with a high degree of cross-linking and increased modulus of the adhesive. Conversely, cohesive failure was associated with reduced cohesive strength of the adhesive layer and a low peel strength.