Rigid polyurethane foams (RPUFs) have been synthesized from high-functional polymeric 4,4'-diphenylmethane diisocyanate (PMDI) and polypropylene glycols (PPG), which were prepared from sorbitol and its combinations with toluene diamine (TDA, T), ethylene diamine (EDA, E), and sucrose/glycerin (G) using environmentally friendly blowing agent, i.e., HFC 365mfc and/or distilled water. Effects of initiator type and blowing agent content have been analyzed in terms of cell morphology, thermal conductivity, and mechanical and dynamic mechanical properties. It was found that TDA-based initiators gave smallest cell, highest value of rubbery plateau modulus, and greatest thermal insulation, whereas EDA gave the greatest dimensional stability. It was also found that the foam properties were largely governed by the blowing agent, whereas initiator gave fine controls of the properties.