Abstract

An aqueous sizing composition for glass fibers and the resultant sized glass fiber strands are provided, where the sized glass fiber strands have an improved slip/flow property and resultant thermosetting articles reinforced with the sized glass fiber strands have improved impact properties. The aqueous sizing composition has a poly(vinyl acetate) silane copolymer, epoxy polymer, one or more lubricants, an organo silane coupling agent, which may be an amino-silane coupling agent, lubricant modified-amino-organo silane coupling agent, epoxy-containing silane coupling agent or a mixture of one or more of these coupling agents, one or more nonionic surfactants, a polyethylene-containing polymer, a wax, a hydrocarbon acid and water. The aqueous sizing composition is applied to glass fibers which are then produced into wet chopped glass fiber strands or continuous sized glass fiber strands. The continuous sized glass fiber strands may be subsequently dried under drying conditions sufficient to remove a substantial amount of the moisture of the strands for subsequent chopping to produce dry chopped glass fiber strands. The sized glass fiber strands have good choppability in that there is not a high amount of fly or fuzz produced during the chopping operation. The sized glass fiber strands in any form may be used for reinforcing thermosetting polymeric material.