The principle of unsaturated polyester resin

Thermoset composites are found everywhere in our daily lives and are known for their excellent strength when exposed to high temperatures or pressure.The most widely known thermoset composites are based on unsaturated polyester resins and are used in a wide range of applications. You may even have some thermoset composite products in your home.

All these composite materials have one thing in common, they are inseparable from Nouryon's organic peroxide metal accelerator during the manufacturing process. When producing thermosetting composite materials, unsaturated polyester resin is mixed with organic peroxide, and the mixture is poured into molds with fillers or reinforcing materials such as fiberglass.The resin begins to harden and form a solid composite material.This process is called curing.

How does the curing process work?Unsaturated polyester resin consists of long-chain polyester dissolved in a solvent such as styrene, where the chains can move freely and cross each other.The curing process begins with the addition of organic peroxides to unsaturated polyester.Under heating conditions, or when reacting with metal accelerators, organic peroxides split into two parts, called free radicals.These free radicals open the double bonds on the styrene molecule and form new free radicals.Another styrene molecule then opens, and the process continues until it encounters an unsaturated polyester chain, the molecules connect, and new groups are formed that can open another styrene or unsaturated polyester chain.This process continues until a group on one chain meets another group and combines.So basically the curing process involves building small styrene bridges between the polyester molecules, and this happens throughout the structure and in all directions.Zooming out further, as the styrene bridge is built, the resin begins to gel and generates heat, which accelerates the reaction. As a result, the curing process becomes faster and faster until most of the styrene molecules have reacted.At this time, the highest temperature is reached and a strong 3D network structure is formed.As the temperature begins to drop, the remaining styrene is added to the network and the final product is now complete and ready for use.