​The Curing of Unsaturated Polyester Resin

Curing Mechanism

    The curing of unsaturated polyester resin refers to the process in which the resin transforms from a liquid to a solid state, a necessary step in using unsaturated polyester resin to manufacture products. This process can be completed under heat and pressure, or it can be carried out at room temperature without heating. On the surface, it appears as a transition from a flowable liquid to a hard solid, but chemically, it is a transition from a linear molecular structure to a three-dimensional molecular structure.

    Commonly used unsaturated polyester resins consist mainly of linear unsaturated polyester and a reactive monomer (usually styrene). Both components contain unsaturated double bonds, which can undergo a free radical copolymerization reaction under certain conditions (such as the addition of peroxide initiators, heating, or exposure to ultraviolet light). This reaction proceeds through the steps of chain initiation, chain propagation, and chain termination. During this process, heat is released, the viscosity of the liquid resin increases rapidly, and its hardness improves, eventually forming a solid that is neither soluble nor fusible. Depending on the requirements, reinforcing materials such as glass fibers may be added during the molding process, or no reinforcement may be added, with only fillers (or no fillers) used. The former results in what we commonly refer to as fiberglass, while the latter can be made into artificial stone products or used as surface coatings.