Study On The Modification Of Polyurethane Insulation Materials For Roofing

In recent years,the whole construction industry is undergoing industrial upgrading.As China enters the new normal of economy,China's construction industry has higher requirements.Rigid polyurethane foam(rigid PUR)has poor flame retardant performance and cannot meet the B1 class fire protection standards.Although the rigid polyisocyanurate foam(PIR foam)has excellent fire performance,it cannot be put into practical application because of its brittle material.Therefore,it is of great significance to improve the flame retardant properties of rigid PUR and enhance the toughness of PIR foam.In terms of rigid PUR foamed plastics,isocyanate and polyether polyol were used to prepare the finished products.Magnesium hydroxide and aluminum hydroxide were selected as flame retardants to modify rigid PUR foamed plastics,and multiple performance indexes were tested for each sample.The results showed that,among the two flame retardants,the comprehensive modification effect of magnesium hydroxide was the best,and the best formula was: isocyanate: polyether polyol: magnesium hydroxide=203:175:28.When the content of magnesium hydroxide gradually increased from 0% to 8.5%,the density of PUR foaming plastics increased accordingly.The strength increased first and then decreased;the water absorption rate and thermal conductivity decreased first and then increased.When the content of aluminum hydroxide increased from 0% to 8.5%,the density and strength of PUR foaming plastics increased,and the water absorption and thermal conductivity decreased.In terms of PIR foamed plastics,the following research had done: using isocyanate pre-polymers with polyester polyol for the preparation of the finished product,and aiming to improve the toughness of PIR foamed plastics,nano Si O2,expanded graphite,cashew phenol as toughening agent on modification.Several parameters of PIR foamed plastics was tested,the results showed that expanded graphite composite modification effect is best,the best formula is: isocyanate pre-polymers: polyester polyol: expanded graphite=120:100:9.When the content of nano-Si O2 gradually increased from 0% to 4%,the effects of nano-Si O2 on the properties of PIR foaming plastics were as follows: the density and strength decreased,the water absorption rate increased,the thermal conductivity increased,and the degree of pulverization increased.When the content of expanded graphite increases gradually from 0%to 6.4%,the density of the sample increases gradually,the strength rises first and then decreases,the absorption of water decreases first and then rises,the thermal conductivity decreases first and then rises,and the degree of pulverization decreases;When the content of cashew phenol increased from 0% to 10%,the density and strength of the sample increased gradually,and the water absorption,thermal conductivity and powder degree decreased accordingly.The effects of foaming environment and foaming temperature on the properties of PIR foamed plastics were discussed.The results showed that the properties of the samplesfoaming in a closed environment were better than that of the samples foaming freely.When the foaming temperature increases from 20? to 40?,the density of the sample increases accordingly,and the strength decreases accordingly.The optimal foaming temperature is 30?.The aging experiment of expanded graphite-modified PIR foamed plastics was carried out,and the storage life of expanded graphite-modified PIR foamed plastics was predicted to be14 years by using the time-temperature equivalence principle and WLF formula.