Abstract
The effects of different mixing regimes on the fracture toughness of polyurethane rubber-toughened polyester resins has been investigated. Variables studied included stirring action, temperature of mixing and rubber content. Two polyurethane rubbers, one hydroxyl terminated and one isocyanate terminated, were studied. It was found that mixing at 60°C and stirring with a laboratory mixer gave the most consistent results in terms of improvement in fracture toughness of the base resin. The optimum rubber content for the hydroxyl terminated rubber was found to be 2.5% w/w while for the isocyanate terminated rubber the optimum rubber content lay between 5% and 7.5%. Both rubber additions produced a decrease in flexural modulus and tensile strength of the base resin, with the hydroxyl terminated rubber giving the greatest decrease.
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