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

• The feasibility of using catechin as a biobased substrate for the synthesis of epoxy resin was studied.
• Formulation of synthesized resins were accomplished with methanol soluble lignin as a natural curing agent.
• The thermal and mechanical properties of green tea catechin based epoxy resins were explored.
• The green tea catechin could be one of the potential substituents to fossil fuel based BPA resin.

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.