New biobased carboxylic acid hardeners for epoxy resins

Supported Ionic Liquid-Phase Materials (SILP) as a Multifunctional Group of Highly Stable Modifiers and Hardeners for Carbon and Flax Epoxy Composites

This paper introduces a novel approach to enhance epoxy resin formulations by using SILP materials as multifunctional hardeners and fillers in composite structures reinforced with carbon and flax fibers. This study explores the integration of ionic liquids (ILs) onto a silica support structure, presenting various permutations involving silica selection, ionic liquid choice, and concentration. The focus of this study was to elucidate the influence of SILP on resin curing ability and the mechanical properties of the resulting composites. Detailed research was conducted, including Brunauer-Emmett-Teller analysis (BET) for SILP materials and curing characterization for epoxy resin formulations with different SILP materials. Furthermore, the mechanical properties of the obtained composites were determined by Scanning Electron Microscopy analysis (SEM) (the force at break, the maximum elongation at break, tensile strength, and modulus of elasticity). Through SILP incorporation, the mechanical properties of composites, including the modulus of elasticity and tensile strength, are substantially improved, a phenomenon akin to traditional filler effects. The findings highlight SILP materials as prospective candidates for concurrent hardening and filling roles within composites (through a single-step procedure, with prolonged storage stability and controlled processing conditions), particularly pertinent as the composite industry veers toward epoxy bioresins necessitating liquefaction via temperature application.

Catalyst-free transesterification vitrimers: activation via α -difluoroesters

Transesterification vitrimers often require high catalyst loadings to achieve 3D networks reprocessable at moderately high temperature. The addition of an activating group close to the ester bonds allows to synthesize...

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

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.

Monitoring the structure–reactivity relationship in epoxidized perilla and safflower oil thermosetting resins

The reactivity of epoxidized perilla oil and epoxidized safflower oil with two aromatic dicarboxylic acids was studied. The presence of S–S bonding at the β position of the carboxylic group increases the reactivity of the acidic proton toward epoxy ring opening.

Optimization of the Curing and Post-Curing Conditions for the Manufacturing of Partially Bio-Based Epoxy Resins with Improved Toughness

This research deals with the influence of different curing and post-curing temperatures on the mechanical and thermomechanical properties as well as the gel time of an epoxy resin prepared by the reaction of diglycidyl ether of bisphenol A (DGEBA) with an amine hardener and a reactive diluent derived from plants at 31 wt %. The highest performance was obtained for the resins cured at moderate-to-high temperatures, that is, 80 ° C and 90 ° C , which additionally showed a significant reduction in the gel time. This effect was ascribed to the formation of a stronger polymer network by an extended cross-linking process of the polymer chains during the resin manufacturing. Furthermore, post-curing at either 125 ° C   or 150 ° C yielded thermosets with higher mechanical strength and, more interestingly, improved toughness, particularly for the samples previously cured at moderate temperatures. In particular, the partially bio-based epoxy resin cured at 80 ° C and post-cured at 150 ° C for 1 h and 30 min, respectively, showed the most balanced performance due to the formation of a more homogeneous cross-linked structure.

Study on the curing reaction kinetics of a novel epoxy system

A novel epoxy system was prepared and the curing reaction kinetics of the system were studied. The thermomechanical properties and mechanical properties in the system were studied and the system shows the best mechanical properties at 10 wt% of FGE.

Multifunctional lubricant additives derived from natural amino acids and methyl oleate

Novel multifunctional additives were synthesized from methyl oleate via thioglycolic acid addition followed by condensation with different amino acid methyl esters.