No abstract

Three different types of environmently friendly blowing agents (HFC 365mfc, HFC 245fa and water) have been used to fabricate rigid polyurethane foams from crude methylene diphenyl diisocyanate and polypropylene glycols. Water induced the earliest bubble, temperature and pressure rises, whereas HFC 365mfc gave the slowest reactivity. Water blown foams showed the largest cell and the lowest density and compression strength, together with the highest glass transition temperature and the greatest dimensional stalibility at high temperature. With the combined effects of large cell and large thermal conductivity of CO 2 , water blown foam gave the highest conductivity of the foam. On the other hand, HFC 365mfc gave the smallest cell size, the greatest foam density and compression strength, whereas HFC 245fa gave the intermediate values, except the lowest thermal conductivity of the foam.