Effects of Reaction Parameters on the Glycidyl Etherification of Bark Extractives during Bioepoxy Resin Synthesis

Abstract

This study outlines the influence of a series of reaction conditions on the yield and reactivity of the glycidyl etherification reaction of the bark extractive-based bioepoxy monomer (E-epoxy). To maximize the yield and epoxy content, the glycidylation reaction was examined with various substrates, solvents, catalysts, time periods, reaction temperatures, and sodium hydroxide/hydroxyl (NaOH/OHV) ratios. Spray-dried bark extractives were used as substrates due to their higher hydroxyl group content and lower molecular weight compared to the oven-dried bark extractives. A dioxane/water combination was selected from among four solvents based on the yield and epoxy equivalent weights of the final product, and tetrabutylammonium hydroxide was chosen as a ring-opening catalyst due to its effect of suppressing hydrolysis. Furthermore, a response surface methodology was applied to find the optimal reaction time, reaction temperature, and NaOH/OHV ratio of the E-epoxy monomer. The maximum extent of conversion with minimum epoxy equivalent weight was achieved after 4.5 h with an NaOH/OHV ratio of 3.4 at 80 °C. This work identifies the effects of reaction parameters on the yield and reactivity of E-epoxy and sheds new light on the glycidylation reaction between epichlorohydrin and renewable biomass.