A bio-based reactive phosphate flame retardant derived from iso-eugenol was synthesized and fully characterized (1 H, 13 C, 31 P NMR, FTIR, MS) with the aim of improving flame retardancy behavior of bio-based epoxy thermosets. This new green flame retardant, diepoxy-iso-eugenol phenylphosphate (DEpiEPP) was then copolymerized either with conventional diglycidylether of bisphenol A resin (DGEBA) or with a totally bio-based glycidylether epoxy iso-eugenol (GEEpiE) resin using a bio-based camphoric anhydride (CA) as hardener. Resulting thermosets with varying rates of flame retardant (1.0 to 4.3 w% phosphorus) were then characterized (FTIR, DSC, nanoindentation, 3-point bending test, TGA, PCFC, cone calorimeter). By this way, a new solution was proposed allowing (i) to increase the bio-based content of thermosets (ii) to improve the flame retardancy properties by a reactive way and (iii) to provide epoxy thermosets with high Tg, excellent mechanical properties and a curing temperature compatible with the use of vegetable fibers. For instance, with a weight content of 2.0 w% P, both GEEpiE-CA-DEpiEPP (95% bio-based content) and partially bio-based DGEBA-CA-DEpiEPP (57% bio-based content) epoxy thermosets possess high Tg (respectively 129 and 105°C), bending elastic modulus and strength of respectively 4.08 GPa and 90 MPa and demonstrate good flameretardant properties due to char promotion showing high promise for application.

Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses and swelling behaviours. This thermoset exhibits a Tg measured by DMA of 165 °C, a tensile storage modulus at 40 °C of 2.2 GPa and mean 3-point bending stiffness, strength and strain at failure of 3.2 GPa, 120 MPa and 6.6%, respectively. Transposed to BioIgenox/hexahydrophtalic anhydride, this optimized formulation gives a thermoset with a Tg determined by DMA of 140 °C and a storage modulus at 40 °C of 2.6 GPa. The thermal and mechanical properties of these two thermosets are consistent with their use as matrices for structural or semi-structural composites.