Preparation Ang Characterization Of Lignin Based Elastomer

Lignin as the storage of the plant community ranked second only to cellulose natural polymer,is a renewable biomass material.As a common by-product of papermaking industry,it is often used to burn and obtain heat,but the real use in the industrial production is so little,which not only causes the waste of resources,but also causes great damage to the environment,and thus how to effectively utilize lignin has become an important research topic.In this paper,lignin was used as the main raw material,and a new type of lignin-based elastomer was prepared by liquefaction of lignin and polyether polyol PPG and PEG in the presence of concentrated sulfuric acid.The preparation process,composition,structure and its effect on the lignin-based elastomer were studied.The result showed that under the condition of liquid-solid ratio 1.8:1,polyols ratio 1:1.2,catalyst content 2%,glycerol content 10%,reaction temperature 120?,curing time 10 h,the lignin-based elastomer had better mechanical properties,the tensile strength was 3.64 MPa and the tensile elongation was 173%,under the condition of the preparation of lignin base elastomer had important effect on the thermal stability and solvent resistance.Increasing the amount of lignin could improve the crosslinking degree of the elastomer and it had rigid structure,so it could improve the tensile strength and solvent resistance.At the same time,the benzene ring of lignin could hinder thermal decomposition,so the thermal stability of elastomer was better,but the chain segment movement was restricted,the elongation decreased.The activity point content of polyol PPG was more than PEG,so it could react with lignin more easily,and the tensile strength,thermal stability and solvent resistance were improved significantly,but the tensile elongation declined due to the increase of crosslinking degree.Sulfuric acid as catalyst could affect the degree of reaction significantly,the liquefaction had better effect with the increase of lignin content,so it could produce more active point,thus the crosslinking reaction wsa more fully,so the tensile strength and solvent resistance were better,while the elongation was decrease.At the same time,the thermal stability decreased because of lignin degradation.Appropriate amount of glycerol could improve the tensile strength and elongation,but it had little effect on thermal stability.Meanwhile,increasing the amount of glycerol was not conducive to solvent resistance because glycerol was soluble in ethanol easily.Increasing the reaction temperature was more conducive to lignification degradation of lignin to produce active sites,thereby enhancing cross-linking degree of lignin-based elastomer,so the tensile strength and solvent resistance increased but the elongation declined.Thermal stability decreased with enhancing liquefaction temperature because lignin degraded into small molecules and capacity of hindering thermal decomposition decreased.The polymerization reaction mainly occurred in the curing stage,so increasing the curing time could improve the tensile strength and solvent resistance,but it was not conducive to the elongation.At the same time,degradation still existed,so the thermal stability decreased.FT-IR showed that there was no chemical reaction between the reactive groups when mixing lignin,polyethylene glycol and polyether polyols directly without high temperature liquefaction,but only physically mixed.At high temperature liquefaction,the esterification reaction occurred in the system,and the reaction degree was further improved in high temperature curing stage.At the same time,the alkylation reaction and condensation reaction occurred in the curing stage.