Compared with the original unsaturated polyester resin varieties, the toughness of the current resin has been greatly improved. However, with the development of the downstream industries of unsaturated polyester resins, more new requirements have been put on the performance of unsaturated resins, especially in terms of toughness. The brittleness of unsaturated resins after curing has almost become an important issue limiting the development of unsaturated resins. Regardless of whether it is from a cast-molded handicraft product or a compression-molded or wound-molded product, the elongation at break has become an important indicator for evaluating the quality of resin products.
At present, some foreign manufacturers use the method of adding saturated resin to improve the toughness. Such as adding saturated polyester, styrene-butadiene rubber and carboxyl-terminated styrene-butadiene rubber, etc., this method belongs to the physical toughening method. It can also be used to introduce block polymers into the main chain of unsaturated polyester, such as the interpenetrating network structure formed by unsaturated polyester resin and epoxy resin and polyurethane resin, which greatly improves the tensile strength and impact strength of the resin This toughening method belongs to the chemical toughening method. A combination of physical toughening and chemical toughening can also be used, such as blending a highly reactive unsaturated polyester with a less reactive material to achieve the required flexibility. At present, SMC sheets are widely used in the automotive industry due to their light weight, high strength, corrosion resistance, and design flexibility. For important parts such as automobile panels, rear doors, and outer panels, good toughness is required, such as automotive exterior. The guard plate can be bent back to a limited extent after being slightly touched and restored to its original state.
Increasing the toughness of the resin often loses other properties of the resin, such as hardness, bending strength, heat resistance, and curing speed during construction. Improving the toughness of the resin without losing other inherent properties of the resin has become an important issue in the research and development of unsaturated polyester resins.