Preparation And Microphase Separation Of Biomass-based Polyurethane Foam

The rigid polyurethane foam is widely used in various fields such as pipeline and building insulation,cold storage construction and cold chain transportation due to its preferable thermal insulation performance.However,with the increasing attention of human beings on environmental protection and the energy problem caused by the large consumption of fossil resources,the development of environmentally friendly biomassbased polyurethane foams derived from lignocellulosic biomass resources has been widely concerned.In this paper,liquefaction technology of biomass was utilized to transform lignocellulosic biomass into biomass-based polyols,and successively biomass-based polyurethane foams.The effect of the addition of lignocellulosic biomass and 1,4-butanediol on the microphase separation degree of polyurethane foams was studied.Biomass-based polyols were prepared with corn stalk as raw material,polyethylene glycol 400 and glycerol as liquefaction reagent and sulfuric acid as catalyst.The effects of liquid-solid ratio,catalyst dosage,reaction temperature and time on the liquefaction yield were studied.The results show that the liquefaction yield of corn stalk could reach95.39% under the optimal conditions.Liquefaction residues was characterized by the infrared spectroscopy(FTIR),thermogravimetric analysis(TG),scanning electron microscopy(SEM)analysis and elemental analysis,and the liquefaction product was characterized by gas chromatograph-mass spectrometry(GC-MS).The results show that the degradation of corn stalk and repolymerization of degradation product are occurred simultaneously during the process of stalk degradation.When the reaction temperature is below 150 °C,the degradation reaction is dominant,while when the reaction temperature is up to 170 °C,the repolymerization reaction plays a dominant role.The biomass-based rigid polyurethane foams were synthesized with biomass-based polyols and polymeric MDI as raw materials.The effect of the isocyanate index,the content of water and foam stabilizer,and the catalyst ratio on the compressive strength and apparent density were investigated.In this case,the compressive strength of the foam was 160.18 k Pa,which is satisfied the mechanical properties requirements of the rigid polyurethane foams and has the potential to be used in the field of thermal insulation.There are carbonyl groups in the derivatives of biomasses.The introduction of the derivatives of biomasses to the biomass-based polyurethane foams increases the number of hydrogen bonds between soft segment and hard segment,and reduces the tendency of microphase separation of polyurethane foam.There are more ordered hydrogen bonds in cellulose-based polyurethane foam and lignin-based polyurethane foam,which increase the tendency of polyurethane microphase separation and improve the thermal stability.The introduction of the 1,4-butanediol can reduce the effect of space steric larger biomass liquefaction product on polyurethane foam and improve hydrogen content in biomass-based polyurethane foam,promote the biomass-based polyurethane foam microphase separation tendency,improve the thermal stability of the biomass-based polyurethane foam,enhance the regularity of the cell hole,whereas decrease the cell closing rate.