Rheological behaviour during UV-curing of a star-branched polyester

Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, BoltornTM and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20.52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50 .C; films can be formed and cured below 80 .C. The crossover of G. and G.. was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.