Rubber Modification of Polyester Resins, 1. Rubber Reactivity and Blend Morphology

Thermosetting polyester resins obtained by polymerization of an unsaturated polyester and a vinyl monomer are known to suffer from certain disadvantages: for example, the impact strength of such materials is rather low. The impact behaviour of such resins may be significantly improved by the addition of suitable liquid rubbers bearing certain terminal chemical groups able to react with the base resin. We have found that the formation of polyester-rubber-polyester block copolymer is of determining importance, together with a very intimate dispersion of the rubbery domains, in the improvement of toughness. An investigation on the influence of formulation and composition, molecular mass of the rubber component, type of functional terminal groups, on the chemistry, morphology and curing behaviour of the prepared blends is reported.