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.

Curing Behavior and Thermomechanical Performance of Bioepoxy Resin Synthesized from Vanillyl Alcohol: Effects of the Curing Agent

“…In recent years, bioepoxies synthesized from natural renewable resources, such as plant oils, rosins, lignin, and lignin derivatives, have been explored [4][5][6][7][8][9]. Among these biomolecules, lignin, which makes up around 30% of woody biomass, was mostly used as a low-grade fuel by the traditional pulp and paper-making industries.…”

Preparation of a Dmap-Catalysis Lignin Epoxide and the Study of Its High Mechanical-Strength Epoxy Resins with High-Biomass Content

“…The catalyst has a significant influence on the epoxy value and molecular weight of the reaction product [ 19 , 20 ]. For the catalysts, the selection is generally based on experimental design.…”

Analysis and Testing of Bisphenol A—Free Bio-Based Tannin Epoxy-Acrylic Adhesives

“…This hardening is accomplished by the addition of a chemically-active curing agent [ 4 ]. Epoxy resins were also produced by the reaction of the corresponding biobased polyols and petroleum-based epichlorohydrin [ 5 , 6 , 7 , 8 ]. Commercialized for more than 50 years, bisphenol A (BPA) is the most common phenol derivative used in epoxy resin formulations to produce adhesives, laminates, structural composites, protective coatings and many other products.…”

“…The reactivity of catechin toward epichlorohydrin to form glycidyl ether derivatives has also been studied. The glycidyl ether of catechin (GEC) thermal properties showed that these new synthesized epoxy resins displayed interesting properties compared to the commercial diglycidyl ether of bisphenol A (DGEBA) [ 5 , 6 , 7 , 8 ]. Major issues today are to find both alternatives to the typical synthesis route for epoxy resins and substitutes for BPA.…”

“…Their source is from forestry or viticulture by-products, thus not in competition with food crops. Resins derived from functionalized natural compounds possess thermal and mechanical properties comparable to those of conventional fossil fuel-derived resins, such as the diglycidyl ether of BPA [ 5 , 6 , 7 , 8 ]. To cure epoxy resins, hardeners, such as an amine or an aldehyde, are usually needed.…”