Study of microgelation of unsaturated polyester resins in the presence of low profile additives by dynamic light scattering

Dynamic light scattering (DLS) experiments were used to study the microgelation of unsaturated polyester (UPE)/styrene resins in the presence of low profile additives (LPA), i. e., poly(vinyl acetate) (PVAC) and poly(methyl methacrylate) (PMMA), during the early stage of the curing reaction. The partially cured resins were mixed with solvents being isorefractive with LPA, thus one “sees” only the primary UPE and the partially cured UPEs in the DLS experiments. The DLS experimental results showed that, during the early stage of curing, the size and structure of the UPE microgels are strongly related to the concentration of LPA and to the compatibility of the components in the curing system. The experimental results of this study revealed the evidence of shrinkage of the microgel particles due to intramolecular crosslinking.