Functionalization of the active ingredients of Japanese green tea (Camellia sinensis) for the synthesis of bio-based epoxy resin

Abstract

The active ingredients of Japanese green tea (Camellia sinensis) were utilized to synthesize bio-based epoxy resin. The catechin compounds in the aqueous extract of green tea were functionalized with epichlorohydrin under alkaline conditions in the presence of tetramethylammonium chloride (TMAC), a water soluble phase transfer catalyst. A good yield of resin was synthesized, and curing was performed with methanol soluble lignin extracted from eucalyptus. The epoxy networks, so synthesized, were compared with bisphenol-A (BPA)-derived epoxy network. The thermal and mechanical properties of the bio-based resin were assessed through thermogravimetric, flexural strength, and glass transition (Tg) analyses. Catechin-based epoxy networks were found to exhibit good thermal and mechanical properties, rendering them potential BPA substitutes. The thermal decomposition temperature resulting in 5% weight loss (Td5) of synthesized epoxy resin was found to be above 300°C, which is slightly lower than that of BPA-derived epoxy resin. The synthesized bio-based resins meet the requirement for the dip-shoulder resistant temperature (250–280°C), with Tg values ranging from 155 to 178°C, highlighting their potential use as one of the most suitable BPA substituents as well as their use in electronic materials.