Study On The Amination Of Lignin And The Curing Of Epoxy Resin With Aminated Lignin

In this paper, the enzymatic hydrolyzed corn straw lignin was used to synthetize lignin amine, and the synthetic process was optimized with four factors and three levels orthogonal experiment. The resulted lignin amine and the polyamine were used to cure the epoxy resin, and the curing kinetics of lignin amine/polyamine-epoxy resin blends was also explored. The effect of resulted lignin amine on the properties of cured epoxy resin was studied.Enzymatic hydrolyzed corn straw lignin and diethylenetriamine were used to synthesize the lignin amine via Mannich reaction, and the effect of single Mannich reaction factor on the amination was investigated. On the basis of this situation, the effect of lignin amine addition on the properties of cured epoxy resin was analyzed. The results showed that the optimized Mannich reaction conditions with best amination performance as follows:the reaction temperature of 90℃, the reaction time of 3h, the mass ratio of NaOH and lignin of 0.07:100, the mass ratio of diethylenetriamine and lignin of 3:10, the mass of formaldehyde and lignin of 1:1. Under this condition, the nitrogen element content of the resulted lignin-amine was 68.6 mg/g.Non-isotherma differential scanning calorinetry(DSC) analysis was used to investigate the curing kinetics of lignin amine/polyamine-epoxy resin blends, and the n-level reaction method of Crane and the most probable mechanism functions of Malek were used to determine the reaction mechanism function of curing system. Simultaneously, the curing kinetic parameters were calculated and the cure kinetic model was fitted. And the curing processing was optimized by extrapolation method. The results showed that the autocatalytic reaction model of Malek was close to the experiment data under the heating rate of 5-20 K/min and more suitable to characterize the cure reaction procedure. For the mixed curing system of lignin amine and polyamine, the optimal curing processing was determined as 90℃ for 2h, and then 130℃ for 1h.Based on the study discussed above, lignin amine was used as curing agents in the epoxy resin-poly amine blends. Non-isothermal differential scanning calorinetry (DSC), dynamic mechanical analysis, thermal gravimetric analysis and mechanical properties test were used to analyze the structure and performance for the cured epoxy resin blends. The results illustrated that the storage modulus (E’), the glass transition temperature (Tg) and thermal stability of the cured epoxy resin increased with the addition of lignin amine. When 3% lignin amine was added, the flexural strength of blends was best. Simultaneously, the aging testing result within the temperature range set in this paper revealed that lignin amine was beneficial to the improvement of anti-aging properties of polyamine/epoxy resin blends.