Research On Dissolution System And Properties Of Novel Alkali Lignin

Lignin is the second most abundant renwable and biodegradable natural resource on the earth after cellouse,which is a complex amorphous aromatic polymer,with the advantages,for example,carbon carbon content,storability,abundance,antioxidant and antibacterial acitvities.Naturally,lignin is considered as the production of alterative chemicals and materials from sustainable biomass resources with low energy and environmental loads,in view of the unique molecular structure and feature.As one of the essential biomasses,lignin has being modifiedinto macromolecular surfactants,depolymerized into platformphenols,developed into natural sunscreens or antioxidants,and is being used in areas such as energy,materials and pharmaceuticals.The main obstacle of lignin is poor solubility during the process of application.Lignin is dissolved by mixed solvent systems consisting of propylene carbonate/water and ?-valerolactone/water,while it is found that the dissolution of lignin is likely to be involved in namely solvent diffusion and chain unwinding,thereby obtaining better the solubleness of lignin.The optimum dissolution of propylene carbonate/water-dissolved lignin is much less than the dissolution time required for the optimal dissolved lignin content of ?-valerolactone/water,and the ratio of propylene carbonate to water is 7:3.Moreover,lignin has an obvious ultraviolet absorption peak due to its own aromatic ring structure at around 200 nm by ultraviolet test.The relationship between lignin solubility and solvation parameters is measured by polarity testing,acquiring hydrogen bond supply capacity or acidity(?),hydrogen bond acceptability or alkalinity(?),and dipolar/polarizability(?*).The ? value is related to the solubility of lignin,rather than a linear relationship.The relationship between ? and ?* values and lignin solubility is smaller than ? value,and ET(30)is related to the polarity of solvent.The propylene carbonate/water dissolved lignin and the ?-valerolactone/water dissolved lignin were analyzed by FT-IR,NMR,DSC,TG and SEM to analysis the structure and performance of lignin.The glass transition temperature higher of propylene carbonate/water dissolved lignin than ?-valerolactone/water dissolved lignin,and embracing better thermal stability.It may be attributed to stronger interaction between the propylene carbonate/water dissolved lignin and mixed solvent,which appeals to obtain more complete lignin,resulting in better performance.Lignin itself has anti-ultraviolet properties,and it is added as an anti-ultraviolet agent to polyethylene(PE)materials to improve the UV aging resistance of PE materials,so that it can be widely applied to production and life as engineering plastic.Obviously,it is discovered that pure PE,PE-Lignin5‰ and PE-Lignin 1% composite materials is prepared by adding 5 ‰ and 1% lignin to the PE material.Through SEM,TG,DMA,DSC,rheological and mechanical properties analysis,it was found that lignin was added.The surface morphology of PE material changed little with the aging time of UV to 800 h,and the surface pores did not increase significantly with the UV aging time.Moreover,the crystallization temperature and melting temperature changed little,and rate of deterioration of the mechanical properties is much smaller than pure PE material.The main reason for the above phenomenon may be that lignin can absorb ultraviolet rays to protect the base PE material from ultraviolet light,thereby protecting the properties of its own material during the ultraviolet aging process.