Effects of Atbn Rubber Additions on the Fracture Toughness of Unsaturated Polyester Resin

Improvement to the fracture toughness of an unsaturated polyester resin and composites by the addition of amine terminated butadiene-acrylonitrile (ATBN) rubber has been investigated. Addition of 6pph ATBN rubber gave a modest gain in fracture toughness of the resin. Electron microscopy studies showed that large agglomerates of a mixture of the rubber and the base resin were formed rather than discrete droplets of the rubber, and this is considered to be the reason for the modest gain in fracture toughness. Unidirectional glass fibre reinforced composites, made with ATBN toughened resin, showed significant gains in inter-laminar fracture toughness. The increased inter-laminar fracture toughness of the rubber modified resin is considered to be due to a combination of localised bonding between rubber/resin agglomerates and the glass fibres, and the lower tensile strength and flexural modulus of the rubber modified resin.