Study On Properties Of Epoxy Resin Co-Cured By Sodium Lignosulfonate

In this paper,lignosulfonate sodium was used as epoxy co-curing agent to prepare lignin/epoxy resin composite.Through the molecular weight degradation of lignosulfonate,the effects of lignin on curing behavior and material properties of epoxy resin before and after degradation were compared,and the curing process was calculated according to the curing kinetic model established.Six kinds of lignin monomermodels were investigated as epoxy curing agents,which provided a theoretical basis for further utilization of lignin in the field of epoxy resin.The imidazole curing accelerator was introduced into the epoxy resin system and EP-LS-(2E4MZ-CN)and EP-(2E4MZ-CN)were mixed in different proportions.The curing kinetics of the system was studied and the properties of the materials were tested.The main results are as follows:(1)The introduction of lignin improves the curing activity of epoxy resin system and degraded lignin with higher activity.The tensile strength,elongation at break and impact strength of EP-DLS rose by 28.7%,52.5% and 53.5%.Lignin could improve the flame retardant property of EP thermosetting resin,while lignin degradation could further improve the flame retardant property.The high performance EP thermoset could be obtained by partially depolymerized lignin as co-curing agents.(2)The reaction activation energy of EP-Ferulic a was the smallest among the six lignin monomers/epoxy resin systems.Compared with lignin monomer without methoxy,the introduction of methoxy improved the tensile property,breaking elongation and impact toughness of EP thermoset.EP-vanillica had the best tensile property and elongation at break,and EP-Syringic a had the best impact strength.EP-vanillica increased the initial weight loss temperature,maximum weight loss rate temperature and carbon residue by 2.6%,1.9% and 25.9%,respectively,compared with EP-(p-Coumaric a).among the six monomers,EP-vanillica had the best thermal stability.EP-vanillica had the highest Glass transition temperature(Tg)of the six EP thermoset.(3)With the increase of EP-LS-(2E4MZ-CN)components,the Ea decreased first and then increased,Thereaction activity of EP-LS-(2E4MZ-CN)was the highest when the component accounted for 20%.With the increase of EP-LS-(2E4MZ-CN)components,the tensile strength decreases gradually.The tensile modulus increased with the increase of EP-LS-(2E4MZ-CN)components.