Rigid polyurethane foams (PUFs) were prepared from polymeric 4,4Ј-diphenylmethane diisocyanate (PMDI), polyether polyol, 1,4-butanediol, silicone surfactant, and distilled water. The properties of the synthesized PUF samples were investigated with differential scanning calorimetry, scanning electron microscopy, and a Universal testing machine. The density of the PUF was decreased from 173.7 to 41.7 kg/m 3 with an increase in distilled water from 0.5 to 3.0 parts per hundred polyol by weight (php), respectively, with 0 php butanediol. The cell size of the PUF sample increased from 115 to 258 m with an increase in distilled water from 0.5 to 3.0 php, respectively, with 10 php butanediol. From the results of the thermal analysis of the PUF sample, it was found that the glass-transition temperatures of the PUF samples were increased from 49.5 to 80.8°C with an increase in distilled water from 0.5 to 3.0 php, respectively, with 0 php butanediol. The results of the investigation of the mechanical properties of the PUF samples showed that the mechanical strength of the PUF samples was increased with the distilled water at equal density. The surfactant effect on the properties of the PUF was studied, and it was observed that the cell size of the PUF samples decreased from 360 to 146 m with an increase in surfactant from 0 to 0.33 php, respectively. However, the cell size did not change significantly when the surfactant exceeded 0.33 php. The increase of the mechanical strength from 0 to 0.33 php surfactant was attributed to the decrease of the cell size of the PUF samples, and the decrease of the mechanical strength with more than 0.33 php surfactant might be due to the plasticized effect of the PUF samples.

Polyurethane foam (PUF)/clay nanocomposites were synthesized with clay modified by polymeric 4,4 0 -diphenylmethane diisocyanate (PMDI) with the application of ultrasound. Transmission electron micrographs showed that the interlayer distance increased for the polyurethane (PU)/ clay nanocomposites where ultrasound was applied. The results of the transmission electron microscopy and X-ray measurements suggest that the application of ultrasound to the clay modification with PMDI improved the efficiency of the clay modification by the effective breakup of the clay agglomerates and intercalation of the silicate layers. In the mechanical tests of the PUF/clay nanocomposites, the flexural and tensile strengths of the PUF/clay nanocomposites showed the maximum value at 3.0 wt % clay content based on PMDI. These results suggest that the increases in the flexural and tensile strengths were perhaps due to the uniform dispersion of the clay by the application of ultrasound. At the same modified clay content, the fire resistance properties were increased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposites without the application of ultrasound. The cell size and thermal conductivity were decreased for the PUF/clay nanocomposites with the application of ultrasound compared to the PUF/clay nanocomposite without the application of ultrasound. Because of these results, we suggest that the smaller cell size and lower thermal conductivity of the PUF/clay nanocomposites were mainly due to the enhanced dispersion of the clay by the application of ultrasound to the mixture of PMDI and clay.

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4Ј-diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X-ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass-transition temperature and change in the heat capacity at glass transition temperature (⌬C p ) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the ⌬C p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers.

Rigid polyurethane foams (PUFs) were prepared from polymeric 4,4-diphenylmethane diisocyanate (PMDI; having functionality of 2.9), polyether polyols, silicone surfactant, amine catalysts, and distilled water. The effects of reactivity on the properties such as density, compressive and flexural strength, and glass-transition temperature (T g ) of the PUF samples were studied. The kinetic rate of forming the PUF samples was increased with the catalyst and water content. With increasing OH value and functionality of the polyols, the density and compressive strength of the PUF samples also increased. For the PUF samples synthesized with polyols having high functionality (Ͼ5), the flexural strength of the PUF samples decreased with the functionality of the polyols. With increasing OH value and functionality of the polyols, the T g of the PUF increased because of an increase in the degree of crosslinking of the PUF samples. The T g value and compressive strength of the PUF samples were observed to increase with the NCO index. From this result, it was suggested that the increase in the T g value and compressive strength of the PUF samples may be attributable to the additional crosslinks that arose from allophonate and biuret formation by the supplementary reactions of excess PMDI.

Polyurethanes were synthesized using the high functional 4,4′‐diphenylmethane diisocyanate (MDI), polyester polyol, and 1,4‐butane diol. The synthesized polyurethanes were analyzed using differential scanning calorimeter (DSC), dynamic mechanical thermal analysis (DMTA), Fourier transform infrared (FTIR) spectrometer, and swelling measurement using N,N′‐dimethylformamide. From the result of thermal analysis by DSC and DMTA, single Tgs were observed in the polyurethane samples at all the formulated compositions. From this result, it is suggested that the polyurethanes synthesized in this study have crosslinked structure rather than the phase‐separated segmented structure because of the high functionality (f = 2.9) of the MDI. By annealing the polyurethane samples using DSC, the Tgs were increased by 4.7∼16.0°C at the various annealing temperatures. From the results of FTIR and swelling measurement of polyurethanes, it is suggested that the increase of Tg of the polyurethanes by annealing is not due to increase of the hydrogen bond strength but mainly due to the increase of the crosslink density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 624–630, 2000