This paper proposes more sustainable alternatives for the synthesis of high thermal performances phenolic networks. Terephthalaldehyde (TPA), a non-toxic aromatic dialdehyde, was selected to replace formaldehyde. Phenol was in turns replaced with bio-based and non-toxic phenolic building blocks: resorcinol as model for tannins, guaiacol which is easily accessible from lignin and tyrosol from olive oil mill wastewaters. The prepolymerization was performed under mild conditions (ethanol, T ≤ 100 °C). The liquid prepolymers were characterized by NMR, IR, MALDI-ToF and rheology. The curing behavior of these formulations was assessed by DSC and IR spectroscopy. An advanced isoconversional analysis of the DSC data allowed the determination of crosslinking activation energies. Furthermore, a multiple-step mechanism of TPA crosslinking was proposed with strong evidences. The thermo-mechanical properties of cured networks were characterized using DMA, showing high crosslink densities and fairly elevated glass transition temperatures. Finally, it has been proven that these new thermosets display very high thermal performances under pyrolysis conditions (TGA). TOCNew sustainable high-performance phenolic thermosets are synthesized from non-toxic and potentially biobased chemicals. We report understanding of curing mechanism and outstanding performances of networks.

The trend towards the utilization of bioresources for the manufacturing of polymers has led industry players to bring to the market new monomers. In this work, we studied 3 polyisocyanates and 2 polyols with high renewable carbon contents, namely L-lysine ethyl ester diisocyanate (LDI), pentamethylene-diisocyanate (PDI) isocyanurate trimer, and hexamethylene-diisocyanate (HDI) allophanate as the isocyanates, as well as castor oil and polypropanediol as the polyols. These monomers are commercially available at a large scale and were used in direct formulations or used as prepolymers. Thermosetting polymers with Tg values ranging from −41 to +21 °C and thermal stabilities of up to 300 °C were obtained, and the polymerization was studied using NMR, DSC, and rheology. Cured materials were also characterized using FTIR, DMA, gel content, and swelling index determinations. These high bio-based content materials can successfully be obtained and could be used as alternatives to petro-based materials.