| With the continuous expansion of the application fields for polyurethane materials,people have put forward new requirements for environmental protection and cost performance.Therefore,the development of biomass based polyols and biomass polyurethane materials with renewable resources has aroused wide interest in academic and industry.The typical process of preparing polyols from biomass is the liquefaction technology.To obtain high liquefaction yield,high temperature and high pressure or efficent catalyst are used at present,which will bring about the increase of the material consumption and energy consumption in the process,and the environmental problems caused by the subsequent process.This study developed an efficient biomass based polyether polyols by solvent thermal liquefaction of corn starch for the first time,with a mixture of polyethylene glycol 200 and glycerol as liquefaction solvent.Effect of reaction temperature,time and liquid-solid ratio on liquefaction were studied.Optimal reaction conditions were as followed:reaction temperature,time and a solid to liquid ratio was 140?C、4.0 h and 1:7,respectively,A liquefaction yield reached 90%.The polyol produced showed hydroxyl number,water content and viscosity were about 331.0 mgKOH/g,430.5 mPa·s and 0.08%,respectively.Secondly,the liquefied product were used for the preparation of rigid PU foam.Under the optimal condition,the densities and compressive strength of PU foam were 72.7 kg/m~3and 150.7 kPa,respectively.The thermal conductivity was 0.024 W/m·K.These properties are comparable to those of the RPU derived from petrochemical based materials and met the industry standard of heat insulation board for rigid polyurethane foam(JG/T314-2012),and national standard(GB10800-1989,GBT8813-2008,GBT6343-2009).After that,The reactive flame retardant polyether polyol was synthesized with melamine formaldehyde resin and 1-Hydroxyethylidene-1,1-diphosphonic acid,and the reactive flame retardant rigid polyurethane foam was prepared.The results showed that the hydroxyl value and viscosity of the flame retardant polyol product was increased compared to the liquefied product without flame retardant treatment.Infrared analysis showed that phosphate ester and three azine ring functional groups existed in the product.The limit oxygen index of the prepared foam reached 26.4,the thermal conductivity was 0.018W/m·K,the compressive strength was 212 kPa,and the apparent density was 78.5 kg/m~3.Finally,a composite flame retardant with starch,1-Hydroxyethylidene-1,1-diphosphonic acid and melamine as carbon source,acid source and gas source respectively was designed and prepared,it was synthesized according to the mass ratio of1:3:5,and added to the foaming system with the addition mass fraction of 20%,the added flame retardant rigid polyurethane foam was prepared.The compressive strength was 164.5kPa,the apparent density was 73.2 kg/m~3,the thermal conductivity was 0.032 W/m·K and the limiting oxygen index is 25.6. |
