A molding composition is provided that includes a thermoset cross-linkable polymeric resin, a fibrous filler and a thickener system. The thickener system includes an amine and an isocyanate that are reactive to form a polyurea. The polyurea is operative to thicken the molding composition formulation prior to polymeric resin thermoset with superior properties relative to conventional thickener systems. A molded article produced from a cross-linked thermoset polymeric resin containing fibrous filler and a polyurea present from 1 to 5 total weight percent of the article either forms an interpenetrating network between the resin and the polyurea or the resin and polyurea crosslink upon resin thermoset to further strengthen the resulting article. An alkali earth oxide or hydroxide simultaneously thickens through interaction with carboxylate functionality of the cross-linkable resin to provide a superior viscosity build and humidity tolerance.