Effect of plasticizers content on the mechanical properties of unsaturated polyester resin

The present work investigates the effect of plasticizers on the mechanical properties of unsaturated polyester (UP) resin. After the curing behavior analysis, several compositions based on UP resin and different amounts of plasticizers are studied. The tensile strength, elastic modulus, elongation at break, impact strength, critical stress intensity factor, hardness as well as glass transition temperature are evaluated as functions of plasticizer content. The results obtained reveal that the impact resistance is maximally improved by approximately 65 and 55%, when 5 and 15 phr dioctyl phthalate (DOP) and tricresyl phosphate (TCP), respectively, are added. The enhancement is more pronounced for the critical stress intensity factor. However, a decrease in hardness and glass transition temperature, but an increase in elongation at break are noticed as expected. In general, TCP compositions exhibit better mechanical properties when compared to that containing DOP. © 2007 SAGE Publications.