Synthesis Of Lignin-based Epoxy Resin And Curing Kinetics Analysis

Lignin is a kind of abundant and recyclable important resource.Industrial lignin is the main components of pulping waste liquor, its world annual production is about50million tons. At present, a large amount of lignin was burned or poured as part of waste water, This will not only result in a waste of resources and cause serious pollution to the environment. It has become a very active research area to utilize lignin in large scale and high value.On the basis comprehensive of literatures, the lignin-based epoxy resin (LGEP) was synthesized using the industrial alkali lignin (LG) as raw material. Firstly, LG was modified by propylene oxide (PO) in2MPa to obtain the hydroxyalkyal lignin (HLG), then HLG reacted with epichlorohydrin (ECH) to synthesize LGEP. The reaction conditions influence on epoxy value (EV) of LGEP were studied and the curing reaction kinetics model of LGEP system was established.Firstly, lignin was purified by the method of alkali-solution and acid-isolation, The hydroxyl value and glass transition temperature (Tg) of alkali lignin were obtained by experimental analysis.Through orthogonal experiment, investigated the mass ratio of ECH to HLG, the mass ratio of KOH to HLG, reaction temperature and reaction time affect on epoxy value(EV) of LGEP; The structure of LGEP was characterized by FT-IR and UV-Vis absorption spectra, The results show that the epoxy group was Successful introduced into LGEP.Then, kinetic parameters of LGEP system were calculated by n order reaction model and the autocatalytic model, and the curing reaction kinetics model of LGEP system were obtained, The results showed that the DSC curves from autocatalytic reaction model was consistent with the experiments curves. According to the characteristic temperature under different heating rates, initial curing temperature Ti0=454.88K, curing temperature Tpo=507.55K, and terminal temperature Tf0=598.77K of LGEP system were obtained by extrapolation method.The results show that the optimum reaction conditions were obtained as follows: the mass ratio of ECH to HLG was3.5:1, the mass ratio of KOH to HLG was1:1, the reaction time was3h and the reaction temperature was80℃. the EV of LGEP reached the highest of0.397and above conditions; Through curing kinetics analysis, the curing time of the LGEP systen with95%curing degree was27.5minutes and the curing time of the LGEP systen with99%curing degree was64.7minutes at the curing temperature507.55K, this provided the basis for optimum curing process.