Synthesis And Properties Of Bio-based Polyurethanes

Biomass resources are widespread in nature,and there is a lack of systematic research on the further comprehensive utilization and development of biological resources.Polyurethane is one of the six important synthetic materials,and the future Chinese market is the biggest engine for increasing demand for polyurethanes.This article provides references for the application of bio-based polyurethanes through the activation and dissolution of biomass materials and the synthesis and performance characterization of bio-based polyurethanes.First,the raw materials of biomass were subjected to physical,chemical and biological activation treatment.After being characterized by electron microscopy,the surface area after activation treatment was increased.After infrared characterization,the materials basically did not change the chemical structure,and the dissolution time was shortened.The ball milling results in a significant reduction in the average particle size of the biomass material.The particle size can be close to the micro-nano level,and the dissolved solid content can be nearly doubled.Then the Ionic liquid and LiCl/DMSO solution were used for dissolution.The maximum solid content of the Ionic liquid dissolved in lignin could reach 32wt%.The solid content of LiCl/DMSO dissolved ball milled lignin could reach 38wt%.The temperature,time and particle size were also investigated.During the experiment,it was found that the viscosity is the limiting factor for further increasing the dissolved solids content.The study found that the LiCl/DMSO system has a low solubility viscosity and is significantly affected by temperature factors.The Ionic liquid system has a relatively large dissolution viscosity and is significantly affected by the particle size.Finally,Polyurethane elastomers and Polyurethane rigid foams were synthesized using biomass as a filler and a polyol substitute.The synthesized microcrystalline cellulose modified Polyurethane elastomer has good thermal stability,and the elongation at break and tensile strength of the elastomer reach a maximum when the amount of microcrystalline cellulose added is 15 wt%;the synthesized lignin-based Polyurethane rigid foam with regular closed pore structure,good density,compression properties,dimensional stability and thermal conductivity,in addition to the addition of cracked lignin enhances the thermal stability of the foam,when added to replace the 50wt%lignin polyol,the foam The limiting oxygen index increased from 21.6 to 23.2,indicating that the foam changes from a flammable material to a combustible material and the flame retardant performance improves.