In situ Measurement of Shrinkage Behavior of Photopolymers

Abstract

Photopolymers have been used in many fields such as adhesion, coating, printing, and electronics. However, UV irradiation leads to volume shrinkage with undesirable influence on adhesive properties and deforming the cured materials. We established a method for in situ measurement of the shrinkage behavior to study the correlation between the volume shrinkage of photopolymers and radical polymerization reaction. The correlation between the amount of reactive acryloyl group and the volume shrinkage in the UV-induced radical polymerization system was examined. The progress of volume shrinkage was linked with the polymerization reaction. However, when the viscosity of a mixed system containing oligomers was >10 Pa⋅s, the diffusion of radical species became slower and the formation of network structure slowed down in the curing sample. It was clear that the mixed systems had a time lag between the polymerization reaction and the shrinkage behavior in the UV-curing process.