“…11 Indeed, formaldehyde remains the most reactive and the shortest aldehyde monomer, which leads to the most densely crosslinked and aromatic networks, suited to high-performances. In response, we have proven that terephthalaldehyde (TPA)a commercially available aromatic dialdehyde which is non-toxic and potentially bio-based, 12,13 can be used as a promising substitute of formaldehyde in resole synthesis (NaOH-catalyzed), even increasing the thermal performances. 14 However, the use of alkali-metal or alkaline-earth-metal hydroxides should be avoided for applications requiring a high thermal stability, such as ablative resoles for aerospace.…”
There is a crucial need to eliminate formaldehyde (F) from high-performance thermoset formulations. We propose herein the study of innovative phenol (P)-terephthalaldehyde (TPA) resole, synthesized under basic conditions. For aerospace applications, alkali-or alkaline-earth-based catalysts should be avoided because they degrade the polymer performances in real conditions. To address this issue, we successfully employed DBU to catalyze the resole formation and compared the mechanisms and performances to the usual NaOH-catalyzed formulation. Insights into the undergoing chemical reactions of crosslinking were given by IR and NMR spectroscopies together with thermal analyses (DSC and TGA). We proposed a two-step mechanism pathway, directly arising from the multiple reactions occurring with TPA (compare to only two with F). An in-depth thermo-kinetics study was efficient to compare both NaOH and DBU catalyzed reactions (performed using multiple heating rates DSC data and isoconversional computational method of Vyazovkin). Finally, TGA results showed that these new resoles presented increased thermal performances compare to commercial PF. TOC This paper presents innovative and highly-performant phenol-terephthalaldehyde thermosets and gives insights into the catalysis and mechanisms of polymerization.
“…11 Indeed, formaldehyde remains the most reactive and the shortest aldehyde monomer, which leads to the most densely crosslinked and aromatic networks, suited to high-performances. In response, we have proven that terephthalaldehyde (TPA)a commercially available aromatic dialdehyde which is non-toxic and potentially bio-based, 12,13 can be used as a promising substitute of formaldehyde in resole synthesis (NaOH-catalyzed), even increasing the thermal performances. 14 However, the use of alkali-metal or alkaline-earth-metal hydroxides should be avoided for applications requiring a high thermal stability, such as ablative resoles for aerospace.…”
There is a crucial need to eliminate formaldehyde (F) from high-performance thermoset formulations. We propose herein the study of innovative phenol (P)-terephthalaldehyde (TPA) resole, synthesized under basic conditions. For aerospace applications, alkali-or alkaline-earth-based catalysts should be avoided because they degrade the polymer performances in real conditions. To address this issue, we successfully employed DBU to catalyze the resole formation and compared the mechanisms and performances to the usual NaOH-catalyzed formulation. Insights into the undergoing chemical reactions of crosslinking were given by IR and NMR spectroscopies together with thermal analyses (DSC and TGA). We proposed a two-step mechanism pathway, directly arising from the multiple reactions occurring with TPA (compare to only two with F). An in-depth thermo-kinetics study was efficient to compare both NaOH and DBU catalyzed reactions (performed using multiple heating rates DSC data and isoconversional computational method of Vyazovkin). Finally, TGA results showed that these new resoles presented increased thermal performances compare to commercial PF. TOC This paper presents innovative and highly-performant phenol-terephthalaldehyde thermosets and gives insights into the catalysis and mechanisms of polymerization.
“…TPA can react four times with phenols (addition and condensation reactions on both aldehyde moieties), yielding highly cross-linked and aromatically dense structures. Furthermore, TPA is nontoxic and is considered as a potentially biobased substance, as it can be obtained via gas-phase oxidation of biosourced para -xylene (a key building block for production of polyethylene terephthalate). , para -Xylene can be obtained by catalytic pyrolysis or hydrocracking of lignin, successive processes using fermentation of feedstock by microorganisms, Diels–Alder reaction, and several other pathways . We have studied in depth the curing behavior of phenol–terephthalaldehyde resoles .…”
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 system not only provides a biosensor-based HT assay for TPA but the first biocatalytic route toward highly reactive TPA-derived aldehydes such as TAL, avoiding hazardous chemical procedures ( Barnicki, 2017 ; Snell and Weissberger, 1940 ). Following the transformation of TAL in the same reaction vessel, the corresponding diamine was yielded and will allow for potential industrial applications ( Brindell et al., 1976 ; Rohan et al., 2015 ; Suematsu et al., 1983 ; Wang et al., 2021 ). Figure 1 Enzyme-coupled biosensor for the detection of TPA in E. coli (1) The biocatalytic degradation of PET by hydrolases releases monomeric molecules including TPA and ethylene glycol (not shown).…”
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