Abstract
The rheological changes during UV curing are examined for solutions of UV-reactive acrylic prepolymer and alkyd resin. To measure the dynamic viscoelasticity in the entire process of UV curing by a single run, a rheological program is developed, by which the storage modulus can be detected in the range of 100-108Pa under linear conditions. The solutions containing alkyd resin at concentrations of 10-30wt% show phase separation in the course of curing. The storage modulus of such systems rapidly increases at first, goes through a maximum and then decreasingly approaches the equilibrium value. The microscopic observation of cured films clearly indicates that the droplets generated by phase separation can grow and migrate in the three-dimensional network. The growth of droplets accompanies the rupture of continuous network in a narrow range. The delicate balance between the local rupture of network by phase separation and formation of crosslinks by polymerization controls the appearance of peak in the time-dependent curve of storage modulus.
