The resin formed by polycondensation reaction of binary or polycarboxylic acid and binary or polyhydric alcohol into polyester resin can be divided into two categories: saturated polyester and unsaturated polyester.
Unsaturated polyester resins are generally linear polymers formed by polycondensation of unsaturated dibasic acids, saturated dibasic acids, and glycols, and contain repeated unsaturation, double bonds, and ester bonds in the resin molecule. Since the unsaturated polyester resin obtained in this way is in a solid or semi-solid state, and cannot be well cross-linked to become a body structure product with good performance, it must be diluted with a cross-linking agent styrene to form a certain viscosity at the later stage of production Resin solution. In fact, the unsaturated polyester resin used is this resin solution, and then the curing agent and other substances are added during use, so that the double bond in the styrene unit and the unsaturated polyester molecule undergoes a radical copolymerization reaction, and finally the crosslink becomes a body structure. Of resin.
It can be seen that the unsaturated polyester resin is a thermosetting resin, and the reaction process of forming the body structure is: the first step generates a linear molecule through the polycondensation reaction of a dibasic acid and a glycol; the second step is in the curing process The body structure is obtained by the free radical copolymerization reaction between the double bond of the resin and the crosslinking agent. This different reaction stage is realized by different functional groups and different reaction mechanisms, which is the characteristic of the synthesis and curing of unsaturated polyester resin.