Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer （NDJ-1 ）, universal testing machine （Instron3365）, s...Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer （NDJ-1 ）, universal testing machine （Instron3365）, scanning electron microscope （SEM） and differential scanning calorimeter （DSC）. The results show that the viscosity of polyether polyol increases exponentially from 62 mPa s to 6 000 mPa s with the increase of functionality from 2 to 5.6, respectively. The overall density of foam increases slightly from 31.7 kg/m^3 to 37.4 kg/m^3 with increasing functionality while core density exhibited little difference. Compressive strength of foam shows the similar behavior with density except for 2-functional sample. At the same time, dimensional stability becomes better with increasing functionality except for 5.6-functional foam that has worse stability than 4.8-functional foam. From the SEM results, the functionality is not an important factor in determining distribution of cell size of foam. According to the results of thermal analysis, the glass transition temperature （T） shifts to a higher temperature from 128.9 ℃ to 166.3 ℃ for the 2 to 5.6 functional foam, respectively.展开更多
Rigid polyurethane foams blown by varying water level were prepared in this study.The structures and physical properties of rigid polyurethane foams blown by water were measured with FT-IR,universal testing machine(In...Rigid polyurethane foams blown by varying water level were prepared in this study.The structures and physical properties of rigid polyurethane foams blown by water were measured with FT-IR,universal testing machine(Instron3365),scanning electron microscope(SEM)and differential scanning calorimeter(DSC).The results show that polyurea and polybiuret were the typical charac-teristics,and the cream time and gel time were shorter for the fully water blown rigid foams than that for the fully cyclopentane blown foams.The density of foam samples decreased from 45.0 kg/m3 to 27.4 kg/m3 with the increase of water level from 3 pph to 7 pph.Compressive strength exhibited the similar behavior with density.The average cell size of foam samples ranged from 241μm to 356μm with the increase of water level from 3 pph to 7 pph,respectively.At the same time,poorer dimen-sional stability was encountered with the increase of average cell size due to fast diffusion rate of CO2 out of the foam.The results of thermal analysis show that the glass transition temperature(Tg)shifted to a higher temperature with the increase of isocyanate level when more water was used as chemical blowing agent.展开更多
基金the Joint Research Foundation of CAS and Hebei Province,China(No.2004-015)
文摘Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer （NDJ-1 ）, universal testing machine （Instron3365）, scanning electron microscope （SEM） and differential scanning calorimeter （DSC）. The results show that the viscosity of polyether polyol increases exponentially from 62 mPa s to 6 000 mPa s with the increase of functionality from 2 to 5.6, respectively. The overall density of foam increases slightly from 31.7 kg/m^3 to 37.4 kg/m^3 with increasing functionality while core density exhibited little difference. Compressive strength of foam shows the similar behavior with density except for 2-functional sample. At the same time, dimensional stability becomes better with increasing functionality except for 5.6-functional foam that has worse stability than 4.8-functional foam. From the SEM results, the functionality is not an important factor in determining distribution of cell size of foam. According to the results of thermal analysis, the glass transition temperature （T） shifts to a higher temperature from 128.9 ℃ to 166.3 ℃ for the 2 to 5.6 functional foam, respectively.
基金Research Foundation of the Chinese Academy of Sciences and Hebei Province,China(Grant No.2004-015).
文摘Rigid polyurethane foams blown by varying water level were prepared in this study.The structures and physical properties of rigid polyurethane foams blown by water were measured with FT-IR,universal testing machine(Instron3365),scanning electron microscope(SEM)and differential scanning calorimeter(DSC).The results show that polyurea and polybiuret were the typical charac-teristics,and the cream time and gel time were shorter for the fully water blown rigid foams than that for the fully cyclopentane blown foams.The density of foam samples decreased from 45.0 kg/m3 to 27.4 kg/m3 with the increase of water level from 3 pph to 7 pph.Compressive strength exhibited the similar behavior with density.The average cell size of foam samples ranged from 241μm to 356μm with the increase of water level from 3 pph to 7 pph,respectively.At the same time,poorer dimen-sional stability was encountered with the increase of average cell size due to fast diffusion rate of CO2 out of the foam.The results of thermal analysis show that the glass transition temperature(Tg)shifted to a higher temperature with the increase of isocyanate level when more water was used as chemical blowing agent.
