Effect of blowing agent type in rigid polyurethane foam

Rigid polyurethane foams have been fabricated from polymeric MDI and polypropylene glycols (PPG) synthesized with two different initiator compositions using two different types of blowing agents, viz., the conventional HCFC 141b and environmently friendly HFC 365mfc. It was found that the two blowing agents gave identically the same cream time, gel time, and tack-free time. The HFC 365mfc gave foams with smaller cell size, greater core density and compression strength, whereas HCFC 141b gave better dimensional stability and thermal insulation. For the same type of blowing agent, the initiator containing more toluene diamine gave greater core density, compression strength and thermal insulation.