Rigid polyurethane foams (PUFs) were prepared from polymeric 4,4'-diphenylmethane diisocyanate, polyester polyol, 1,4-butane diol, silicone surfactant, hydrochlorofluorocarbon (HCFC) 141B, and distilled water. The properties and structure of the PUFs were investigated with differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and a universal testing machine. The density of the PUF blown by distilled water and/or HCFC 141B decreased from 175.7 to 28.2 kg/m(3) with an increase of blowing agents. From the SEM results, the average cell size of the PUF blown by distilled water increased from 150 to 290 mum with the distilled water content. From the DSC results, the glass-transition temperature (T-g) of the PUF blown by distilled water increased from 85.7 to 101.7 degreesC with increasing distilled water content, whereas the T-g of the PUF blown by HCFC 141B remained unchanged with HCFC 141B content. The compressive strength and modulus of the PUF blown by a mixture of distilled water and HCFC 141B was increased from 0.13 to 0.25 MPa and from 3.00 to 7.23 MPa, respectively, with the distilled water content at the sample density of about 44.0 kg/m(3). The increase of the compressive strength and modulus of the PUF at the same density was related to the increase of the T-g from 86.0 to 100.9 degreesC.