Research On Modification And Damp-heat Characteristics Of Salix Liquefaction Product/Isocyanate Foam

In this thesis,self-made Salix psammophila liquefaction product and isocyanate were used as main raw materials,and Salix psammophila liquefaction product/isocyanate rigid foam material(RPUF)was prepared by copolymerization method,and the physical and mechanical properties of RPUF were improved by cross-linking modification technology.Effects of damp-heat conditions on mechanical attenuation,morphological changes and chemical structure of modified polyurethane foams.The main conclusions are as follows:1.The properties of RPUF modified by crosslinking agents trimethylolpropane(TMP)and triethanolamine(TEOA)showed that the compressive strength and impact strength reached the maximum at 2%,and the strength of TMP was higher than that of TEOA,which were 2.45MPa and 1.86k J/m~2respectively.The overall trend of infrared spectrum before and after RPUF modified by crosslinking agent was basically similar.The addition of TMP made the cell smaller;The addition of TEOA made the cell morphology poor.The initial decomposition temperature of foam materials decreased and the residual carbon content increased.TMP had better comprehensive properties for polyurethane foam.2.RPUF could conduct moisture absorption reaction under the influence of damp and heat conditions,but the overall mass changed shall not exceed±0.5g.The mechanical properties were different under different temperature and humidity conditions.The compressive strength reached the maximum value of 0.53 MPa at 75℃and 30%RH,and reached the minimum value of 0.25MPa at 25℃and 50%RH;the bending strength reached the maximum value of 0.89MPa at 75℃and 50%RH,and reached the minimum value of0.61MPa at 25℃and 85%RH;the impact strength reached the maximum value of 2.50k J/m~2at 75℃and 50%RH,and reached the minimum value of 0.33 k J/m~2at 10℃and85%RH.The C=O vibration was more obvious after damp heat treatment.The increase of temperature could promote the autocatalysis of the system,aging the cell surface;the increase of humidity could promote the hydrolysis reaction,resulting in water absorption and wrinkling on the surface of the cell.3.After different stages of changes and different cycles of wet heat treatment of RPUF,it was concluded that:(1)The change trend of mechanical strength of RPUF in different stages was basically the same,at the stage of increasing temperature and humidity,the impact strength increased the most which was 32.62%;at the stage of equal humidity and temperature increased,the bending strength rebounded the most which was 37.8%.There was no new characteristic peak in the infrared spectrum,it was indicating that there was no new change of chemical structure.(2)From the dry state to the end of the cycles,the overall trand of compressive strength、bending strength and impact strength showed a decrease,and the decline rates were 50.63%,42.55%and 48.31%,respectively.RPUF did not produce a new chemical structure.After the cycles of damp heat,some of the thinner cell walls fall off,and even cell rupture and foam spine fracture occur.After four cycles,the initial decomposition temperature dropped to 25.96℃,and the residual carbon rate dropped to 24.44%.