A string binder is disclosed which is useful for making reinforcing articles for use in the manufacture of molded composite articles. The string binder comprises a fibrous substrate with chemical treatment, applied thereto, comprising a polyester resin, a curing agent, a film former, and a thickener. Additionally, the string binder may be co-roved with one or more ends of a separate fibrous pre-form material to make a product suitable for use in various molding applications.