Preparation of UV‐thermal dual curable environmentally friendly polyacrylate pressure‐sensitive adhesives by bulk polymerization

Three different acrylate monomers containing butyl acrylate, 2-hydroxyethyl acrylate, and acrylic acid were designed to synthesize polyacrylate pressure-sensitive adhesives (PSAs) by bulk polymerization process initiated via radical photo-initiators under UV irradiation and UV-thermal dual curing. Thermal crosslinker, KL-1202, with trifunctional isocyanate groups was introduced into the prepolymer to form an intermolecular crosslinking network structure. An emphasis was placed on the effect of the KL-1202 content on the microstructure and adhesive properties of PSAs. The viscosity and composition of prepolymer synthesized by UV initiation were tested by a rotational viscometer and Fourier transform infrared spectroscopy, respectively. The degree of crosslinking of the final PSA was evaluated by the gel content value obtained via Soxhlet extraction, while the molecular weights of the soluble parts of PSA polymers were measured by gel permeation chromatography. Dynamic mechanical analysis was used to characterize the viscoelastic performance of PSAs. Moreover, the adhesive properties of PSAs were determined through a series of tests including loop tack force, peel force, and shear resistance. It was found that the C=C double bond and the isocyanate group disappeared after UV radiation and thermal curing process. Dual-cure acrylate PSAs compensate for limitations in UV-induced cure of thick coatings. The T-g value, storage modulus (G '), and shear resistance of PSAs were improved while the loop tack force and peel force of PSAs decreased as the KL-1202 content increased.