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Unsaturated polyester resin is one of the most widely used resins in the marine industry and other sectors, divided into two categories: orthophthalic polyester resin and isophthalic polyester resin. Most hunting boats, sailboats, and cargo boats in the composite industry are made using this resin system.
In 1929, Arvin and Carothers created unsaturated polyester resins from maleic acid and ethylene glycol at temperatures of 175-185°C. Subsequently, unsaturated polyester resin has been dramatically used for a wide range of applications, making it an important thermoset system.
**Characteristics of Unsaturated Polyester Resin**
Important properties of this polymer include:
– Heat resistance and dimensional stability against temperature changes
– High tensile and compressive strength
– High flexural strength
– Resistance to corrosion and chemical agents
– Excellent dielectric properties
– Good fluidity when heated
– Wear resistance
– Good mechanical strength
A manufacturer can supply the resin either pure or with any of the above additives. Resins are easily formulated by adding a catalyst before molding, depending on the molding requirements. As previously mentioned, given sufficient time, unsaturated polyester resin can undergo the curing process spontaneously. The speed of this polymerization is very slow for high-volume parts, so a catalyst is used to achieve a specific and practical polymerization time. The catalyst is added to the resin system shortly before the polymerization reaction begins; it does not participate in the chemical reaction but simply activates the process. Since accelerators have little effect in the absence of a catalyst, polyester manufacturers sometimes add the accelerator to the resin and supply it as pre-accelerated resin.
