Study On The Synthesis Of Lignin-Based Epoxy Syntactic Foam

Facing the increasing crisis of worldwide environmental pollution and resource shortage, mankind has to reevaluate his behavior and efficiency in utilizing natural resources. Lignin, whose reserve in the world is just next to cellulose, was formerly abandoned as by-products of pulp and paper industry. Every year, the industry produces about 50 million tons of lignin. Furthermore, the nature regenerates lignin at the remarkable speed of 150 billion tons per year. While the overuse of petroleum and coal has been causing numerous environmental problems and resource crisis, no best use of lignin has been made. However, as time goes by, lignin is properly valued all over the world. It is now of more and more significance as industrial materials, especially in the field of renewable and degradable synthetic polymers. Sooner or later, they will play an important role, or even make a history in the field just mentioned.To synthesize lignin-based epoxy syntactic foam, hydroxyalkyl lignin was prefabricated from lignin and epoxypropane firstly. As a result, the amount of alcohol hydroxyl was increased clearly, while the amount of phenolic hydroxyl was decreased sharply. The hydroxyalkyl lignin was analyzed by IR, and the mass ratio of lignin to epoxypropane was ascertained at 1 to 4.Secondly, hydroxyalkyl lignin were epoxidized by epichlorohydrin with boron trifluoride etherate as catalyst. Based on the results of some searching-after experiment, the adopted volume of boron trifluoride etherate was 0.4 mL per 10 gram hydroxyalkyl lignin. While the mass ratio of potassium hydrate and epichlorohydrin to hydroxyalkyl lignin were 0.7 and 1.96, the etherification and cyclization hours were five and one. Under this experimental condition, the epoxy value of lignin-based epoxy resin reached o.24.Finally, two kinds of hollow microspheres were blent into the aforementioned lignin-based epoxy resin respectively, with TETA or T-31 as curing agent and Al-Sodium hydroxide as foaming system. All the mixed reactants were placed under certain temperature. After several curing hours, the lignin-based epoxy syntactic foams were synthesized. The mechanical properties of the foams show that the filling of certain hollow microspheres can effectively increase both the impact strength and bend intensity of the lignin-based epoxy syntactic foams.