Synthesis of Pluri-Functional Amine Hardeners from Bio-Based Aromatic Aldehydes for Epoxy Amine Thermosets

Abstract

Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use of the reductive amination with imine intermediate in order to obtain bio-based pluri-functional amines exhibiting low viscosity. The effect of the nature of initial aldehyde reactant on the hardener properties was studied, as well as the reaction conditions. Then, these pluri-functional amines were added to petro-sourced (diglycidyl ether of bisphenol A, DGEBA) or bio-based (diglycidyl ether of vanillin alcohol, DGEVA) epoxy monomers to form thermosets by step growth polymerization. Due to their low viscosity, the epoxy-amine mixtures were easily homogenized and cured more rapidly compared to the use of more viscous hardeners (<0.6 Pa s at 22 °C). After curing, the thermo-mechanical properties of the epoxy thermosets were determined and compared. The isophthalatetetramine (IPTA) hardener, with a higher number of amine active H, led to thermosets with higher thermo-mechanical properties (glass transition temperatures (Tg and Tα) were around 95 °C for DGEBA-based thermosets against 60 °C for DGEVA-based thermosets) than materials from benzylamine (BDA) or furfurylamine (FDA) that contained less active hydrogens (Tg and Tα around 77 °C for DGEBA-based thermosets and Tg and Tα around 45 °C for DGEVA-based thermosets). By comparing to industrial hardener references, IPTA possesses six active hydrogens which obtain high cross-linked systems, similar to industrial references, and longer molecular length due to the presence of two alkyl chains, leading respectively to high mechanical strength with lower Tg.

High Glass Transition Materials from Sustainable Epoxy Resins with Potential Applications in the Aerospace and Space Sectors

“…On the basis of research and technical requirement from industry, these resins can be considered suitable for hard material applications such as in the automotive industry. − The designed TGPh-based resins can successfully be used to replace the fossil-derivatives-based materials for structural aerospace components. , The obtained glass transitions for the designed resins can be comparable with the following commercial products: Park Aerospace Nelco N5000-30/32 BT, T g = 205 °C; Park Aerospace Nelco N4000-29, T g = 185 °C; Dow VORAFORCE TW 103/TW 158, T g = 175–185 °C; Henkel Hysol Benzoxazine 99110, T g = 191 °C; Hexcel HexPly 108, T g = 190–210 °C.…”

Bio-Based Furanic Di(meth)acrylates as Reactive Diluents for UV Curable Coatings: Synthesis and Coating Evaluation

“…The T d 5% value for the control HDDA coating is higher than those of the FDA- and FDMA-based coatings, which indicates that the furan-based diluents lead to somewhat lower thermal stability than that of HDDA (e.g., Figure ). As shown in Table , all furan-based coatings except for FDMA-8-based coating had higher char yields than that of the control HDDA sample, which is likely due to the aromatic nature of the furan rings. − As shown in Figures S92–S99, the cured coatings using acrylates as diluents have similar thermal stability to that of the methacrylate diluents. As shown in Table , in all furan-based UV-cured samples, the samples prepared from furan-based diluents containing allyl groups (e.g., FDA-4, FDA-5, FDMA-4, and FDMA-5) exhibit higher thermal stability with higher T d 5% values than those of the samples prepared from furan-based diluents containing alkyl or cyclic substituted groups, which may indicate that the allyl groups are involved in the UV curing process via chain transfer reactions and increase the stability of the cured samples.…”

Bio-sourced alternatives to diglycidyl ether of bisphenol A in epoxy–amine thermosets

“…Mora et al synthesized new aromatic-containing amines and cured DGEVA and DGEBA for comparisons. 57 They reported lower thermal stability for all DGEVA-based thermosets (T d5% ) but higher char yields. Glass transitions temperatures and T α were also lowered with DGEVA compared to DGEBA.…”