Abstract
The development of epoxy thermosets from renewable resources is of paramount importance in a sustainable development context. In this paper, a novel bio-based epoxy monomer derived from limonene was synthesized without epichlorohydrine and characterized. In fact, this paper depicts the synthesis of bis-limonene oxide (bis-LO). However, intern epoxy rings generally exhibit a poor reactivity and allow reaction with anhydride. Therefore, we used a reaction model with hexahydro-4-methylphthalic anhydride to compare reactivity of terminal and interepoxy functions. We also studied the influence of methyl group on intern epoxy functions. Furthermore, the influence of epoxy:anhydride stoichiometry and initiator amount was studied. These studies allow to propose an optimized formulation of bis-LO. Finally, a bis-LO-based thermoset was obtained and characterized.
Highlights
With the decrease of available fossil resources, ensuing price volatility, and the increasing awareness regarding environmental and human health protection, a booming amount of research has been carried out to find alternative to fossil-based chemicals
Cyclohexene oxide (98%), (+)-Limonene oxide, mixture of cis and trans (97%), 3,43,4-epoxycyclohexanecarboxylate, 2-ethyl-4-methylimidazole (95%), hexahydro-4-methylphthalic epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 2-ethyl-4-methylimidazole (95%), hexahydro-4-methylphthalic anhydride, mixture of cis and trans (96%), phenyl glycidyl ether (96%), diglycidyl ether of bisphenol A (DGEBA), and ethyl acetate were supplied by Sigma-Aldrich (Saintanhydride, mixture of cis and trans (96%), phenyl glycidyl ether (96%), diglycidyl ether of bisphenol A (DGEBA), and ethyl acetate were supplied by Sigma-Aldrich (Saint-Louis, MO, USA)
We propose to clarify the impact of the epoxy/anhydride ratio and the amount of the catalyst on the glass transition temperature, for two thermoset models bis-cyclohexene oxide (bis-cyclohexene oxide oxide (CHO))/hexahydro-4-methylphthalic anhydride (HMPA) and DGEBA/HMPA, in presence of EMI as catalyst
Summary
With the decrease of available fossil resources, ensuing price volatility, and the increasing awareness regarding environmental and human health protection, a booming amount of research has been carried out to find alternative to fossil-based chemicals This statement is especially true for thermosetting polymers (or thermosets), which represent about 20% of the global plastic production with a large number of applications. Among potential bio-based molecules, limonene (Scheme 1) appears as an interesting candidate It is a cyclic monoterpene derivative found in many citrus fruits [18]. Depending on the processed into juice or estimated million tons of citrus world-wide fruit variety, season and geographic origin, a variable amount of limonene can be extracted, generally [19].
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