Shrinkage in UV-Curable Coatings

The chapter first describes fundamentals and applications of UV-curing technology and brings out the most important problem in this area: shrinkage. In the following text, the reason for shrinkage formation, its influence in UV-curing, and the methods to measure the shrinkage are described. The methods reviewed include dilatometry, pycnometer, buoyancy, bonded-disk, interferometer, laser displacement, laser scanning, video-imaging device and some combined methods. After that, several ways to control or overcome the problem of shrinkage are summarized, including changing the condition of UV-curing, adding an inert component, adjusting the structure of monomers, such as decreasing the density of functional groups, introducing rigid structure, applying ring-opening polymerization, using thiol-containing system and hybrid system (e.g., free-radical/cationic hybrid system, thiol-ene/acrylate hybrid system and organic/inorganic hybrid system), and adopting solid-state photopolymerization. The developing prospects of the research for shrinkage in UV-curable coatings are given in the concluding section.