An anti-shrinkage model of an ultraviolet-curing coating filled with hollow polyurethane acrylate microspheres

The application of ultraviolet (UV)-curing coatings in precision devices is restricted because of their high shrinkage performance. In this study, hollow polyurethane acrylate (PUA) microspheres are filled into a mixed tripropylene glycol diacrylate (TPGDA) coating with different volume fractions to regulate shrinkage ratios of the coating, where hollow PUA microspheres with different diameters and thicknesses are synthesized using the microfluidics technology. The thickness-dependent mechanical properties of PUA thin films (the same thickness with the shell of each microsphere) are obtained by combining in-situ tensile and nanoindentation experiments with finite element (FE) method. The empirical formula between geometrical parameters (diameter, shell thickness, volume fraction) of hollow PUA microspheres and shrinkage ratios of the TPGDA coating filled with these PUA microspheres are derived using the present representative volume element (RVE) method. Checking against the results of UV-curing shrinkage experiments shows the current empirical formula has high accuracy. This study provides a physical insight into modulating their shrinkage ratios of different UV-curing materials.