The entire curing process of unsaturated polyester resin consists of three stages:
Gel - from a viscous fluid resin to a loss of fluidity to form a semi-solid, elastic gel;
Qualitative - from the gel to a certain hardness and fixed shape, the cured product can be removed from the mold without deformation;
Curing - has stable chemical and physical properties and achieves high degree of cure.
The curing process of all active linear oligomers can be divided into three stages, but due to the different mechanisms and conditions of the reaction, the characteristics of the three stages are different. The curing of the unsaturated polyester resin is a free radical copolymerization reaction, and therefore has the property of a chain-locking reaction, which is manifested in three stages, and the time interval has a short characteristic, and generally the gel to the setting can be completed in a few hours. In addition, the unsaturated polyester has no extra small molecules in the system during curing, and the structure is relatively tight. Therefore, the unsaturated polyester resin has the best room temperature contact molding process performance compared with other thermosetting resins.Back