Study of the reaction of polyester resins with magnesium oxide

Abstract

Abstract The reaction of polyester resin and magnesium oxide, which is the basis of the thickening process of sheet‐molding compound technology, has been characterized in a systematic study. The effect of reactant equivalency ratios, temperature, and added water on viscosity development have been determined. Excess amounts of magnesium oxide are necessary for thickening. Water increases the initial rate of thickening but reduces the overall level attained. A new thickening mechanism is proposed on the basis of a model study with polyester resin and sodium hydroxide.