Dual Cross-linking of Epoxidized Linseed Oil with Combined Aliphatic/Aromatic Diacids Containing Dynamic S−S Bonds Generating Recyclable Thermosets

Abstract

The end-of-life of thermoset materials is a real issue that confronts our society, and the strategy of introducing dynamic reversible bonds can be a sustainable solution to overcome this problem. This study shows an efficient way to produce biobased and recyclable thermosets, for a circular use. To reduce the production costs linked to energy and duration, an improved curing process is proposed by combining aromatic and aliphatic diacid hardeners containing dynamic S–S bonds. The work demonstrates the increased reactivity of epoxidized vegetable oil reacted with the two diacids. The structural evolutions during the exchange reactions that allow the recyclability were followed by Fourier transformed-infrared and nuclear magnetic resonance spectroscopies, high-performance liquid chromatography, and mass spectroscopy. The curing process was studied by differential scanning calorimetry and kinetic study.

Recyclable High-Performance Epoxy-Anhydride Resins with DMP-30 as the Catalyst of Transesterification Reactions

“…The development of vitrimers containing dynamic covalent bonds (DCBs) makes it possible to recycle thermosets under mild conditions [ 8 , 9 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Over the past few decades, researchers have developed an array of vitrimers through incorporating various DCBs (e.g., disulfide [ 25 , 26 ], imine-amine exchange [ 27 ], and hindered urea bond [ 28 ]), among which epoxy vitrimer prepared from the curing reactions of epoxy-anhydride [ 29 , 30 , 31 ] or epoxy-carboxylic [ 32 , 33 , 34 ] is the most investigated vitrimer system. The network topology can be rearranged via transesterification reactions (TERs) between ester bonds and hydroxyl groups at elevated temperatures, leading to the unique properties of materials such as malleability, self-healing, or reprocessability [ 21 , 29 , 35 , 36 , 37 , 38 ].…”

“…The development of vitrimers containing dynamic covalent bonds (DCBs) makes it possible to recycle thermosets under mild conditions [8,9,[15][16][17][18][19][20][21][22][23][24][25]. Over the past few decades, researchers have developed an array of vitrimers through incorporating various DCBs (e.g., disulfide [25,26], imine-amine exchange [27], and hindered urea bond [28]), among which epoxy vitrimer prepared from the curing reactions of epoxy-anhydride [29][30][31] or epoxycarboxylic [32][33][34] is the most investigated vitrimer system.…”

Influence of the Presence of Disulphide Bonds in Aromatic or Aliphatic Dicarboxylic Acid Hardeners Used to Produce Reprocessable Epoxidized Thermosets

“…This result can be correlated and explained by the electron-donor character of the aliphatic chain of DTDA that increases the electron density in the carboxylate anion (RCOO − ) and therefore decreasing the formation of reactive species. In contrast, DTBA, as demonstrated by our team, increases the selectivity control for the propagation reaction between epoxy acid with the carboxylic–carboxylate complex formation [ 31 ].…”

Sustainable Thermosets and Composites Based on the Epoxides of Norbornylized Seed Oils and Biomass Fillers

“…Currently, epoxidized seed oils are only being used for specialty coating applications, additives, plasticizers, and stabilizers. 36,37 It was modified by acrylates, 38−41 bismaleimide, 42,43 DGEBA, 44,45 multifunctional thiols, 46,47 anhydrides, 47 and diacids 48,49 for thermoset and coating applications. Among the composites from epoxide seed oils, silica-filled 50 and vegetable fiber composites 51 are reported.…”