Mechanical, Morphological and Thermal Properties of Rigid Polyurethane Foam : Effect of Chain Extender, Polyol and Blowing Agent

The properties of rigid polyurethane foams can be modified over a wide range depending on the raw materials used for its synthesis. The polyols, chain extender and blowing agent have major impact on the properties of the PUF. This investigation reports the effect ofpolyol and its blends, chain extender such as 1, 4-butanediol (1, 4-BD) and blowing agents [chemical as well as physical; such as distilled water and n-pentane (n-C5), hydrochlorofluorocarbon (HCFC)] on the properties of rigid PUF. Addition of the chain extender improves the mechanical properties initially but then it decreases the properties on further addition of the same. The thermal conductivity of the chain extended and that of the physically blown PUF was lower than the water blown PUF. Higher loading of chain extender and blended polyol decreased the glass transition temperature (Tg) of the PUF due to the decrease in cross-link density because of low -OH functionality in the presence of linear diols like hydroxyl terminated polybutadiene (HTPB). It was observed that there is no significant change in degradation temperature of the chain extended, physically blown and blended system except that observed in the case of HTPB filled PUF.