Unsaturated polyester and vinyl ester resins are widely used in open mold process such as hand lay-up, spray-up, non-reinforced castings, gelcoats and filament winding. To achieve high reactivity, reasonable viscosity and high performance, certain amount of styrene is generally used with these types of resins. However, new environmental concerns demand reduction and better control of styrene emissions into the environment. Several methods have been proposed as possible ways to reduce styrene to minimize monomer emissions during the curing process of unsaturated polyesters or vinyl esters. One common method is the replacement of styrene by another reactive diluent that can produce fewer emissions during curing. This approach can lead to systems with slower reactivity, incomplete curing and higher costs. Another approach involves the preparation of low molecular weight polymers that require lower amount of styrene or diluents. Problems associated with lower molecular weight thermosetting systems are that the resulting physical properties of the final products are often compromised. This paper presents a study of a new vinyl-functionalized polyester oligomer with no styrene and other reactive diluents in the composition. In comparison with typical unsaturated polyester systems, the new material has zero styrene content, low HAPS, and low shrinkage. In addition, the new styrene free material maintains expected properties of typical styrene-containing unsaturated polyester systems such as high reactivity, low viscosity, good wetting and compatibility with fiberglass, rapid development of hardness, and good mechanical properties. This new material also has very good color and excellent stability at both room temperature and 65oC oven. In depth performance data will be presented in this paper.
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