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 (AT BN) rubber has been investigated. Addition of 6pph ATBN rubber gave a modes t gain in fracture toughness of the resin. Electron microscopy studies show ed that large agglomerates of a mixture of the rubber and the base resin we re formed rather than discrete droplets of the rubber, and this is consider ed to be the reason for the modest gain in fracture toughness. Unidirection al glass fibre reinforced composites, made with ATBN toughened resin, showe d significant gains in inter-laminar fracture toughness. The increased inte r-laminar fracture toughness of the rubber modified resin is considered to be due to a combination of localised bonding between rubber/resin agglomera tes and the glass fibres, and the lower tensile strength and flexural modul us of the rubber modified resin.