Examining the effects of storage on the initiation behaviour of ionic liquids towards the cure of 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.

VOC-free tricomponent reaction platform for epoxy network formation mediated by a recyclable ionic liquid

VOC-free mild conditions curing reaction of a petroleum-based epoxy (DGEBA) or a bio-based epoxy (DGEMHQ) in a tricomponent reaction platform with a recyclable imidazolium-based IL (BMImCl) and dicarboxylic acid (succinic acid).

Magnetic Ionic Liquid Nanocatalyst to Improve Mechanical and Thermal Properties of Epoxy Nanocomposites

New magnetic imidazolium ionic liquid (IIL) was synthesized to improve the curing, mechanical, and thermal characteristics of the epoxy/polyamine system. In this respect, 2-(4-minophenyl)-1.3-bis(triethoxysilyl)-1H-imidazol-3-ium acetate as IIL was synthesized and characterized by different spectroscopy tools. The IIL was used as capping to prepare Fe₃O₄ nanoparticles (NPs) as new Fe₃O₄-IIL NPs. The thermal stability, morphology, crystal lattice structures, and magnetic properties were evaluated to confirm the formation of uniform, thermal, stable, and superparamagnetic Fe₃O₄-IIL NPs. The prepared Fe₃O₄-IIL NPs were mixed with an epoxy/polyamine system to improve the curing, thermal, and mechanical properties of epoxy through chemical reactions. The dynamic mechanical analyzer and differential scanning calorimeter were used to investigate the flexibility and storage modulus of the cured epoxy/polyamine system in the absence and presence of Fe₃O₄-IIL NPs. The atomic force microscope and scanning electron microscope were used to evaluate the dispersion and embedding of Fe₃O₄-IIL NPs into epoxy matrix. The thermal, mechanical, and surface morphologies data confirmed that the incorporation of Fe₃O₄-IIL NPs using 3 wt. % during the curing of an epoxy/polyamine system produces superior epoxy films without cracks, holes, and NPs agglomeration.

Impact of Imidazolium-Based Ionic Liquids on the Curing Kinetics and Physicochemical Properties of Nascent Epoxy Resins

We investigated the influence of anion type (salicylate, [(MOB)MIm][Sal], vs chloride, [(MOB)MIm][Cl]) of imidazolium-based ionic liquid (IL) and its content on the curing kinetics of bisphenol A diglicydyl ether (DGEBA of molecular weight M n = 340 g/mol). Further physicochemical properties (i.e., glass transition temperature, T g, and conductivity, σdc) of produced polymers were investigated. The polymerization of the studied systems was examined at various molar ratios (1:1, 10:1, and 20:1) at different reaction temperatures (T reaction = 353-383 K) by using differential scanning calorimetry (DSC). Interestingly, both DGEBA/IL compositions studied herein revealed significantly different reaction kinetics and yielded materials of completely distinct physical properties. Surprisingly, in contrast to [(MOB)MIm][Cl], for the low concentration of [(MOB)MIm][Sal] in the reaction mixture, an additional step in the kinetic curves, likely due to the combined enhanced initiation activity of anion (salicylate)-cation (imidazolium-based), was noted. To thoroughly analyze the kinetics of all studied systems, including the two-step kinetics of DGEBA/[(MOB)MIm][Sal], we applied a new approach that relies on the combination of the two phenomenological Avrami equations. Analysis of the determined constant rates revealed that the reaction occurring in the presence of the salicylate anion is characterized by higher activation energy with respect to those with the chloride. Moreover, DGEBA/[(MOB)MIm][Sal] cured materials have higher T g in comparison to DGEBA polymerized with [(MOB)MIm][Cl] independent of the IL concentration. This fact might indicate that, most likely, the products of hardening are highly cross-linked (high T g) or oligomeric linear polymers (low T g) in the former and latter cases, respectively. Such a change in the chemical structure of the polymer is also reflected in the dc conductivity measured at the glass transition temperature, which is much higher for DGEBA cured with [(MOB)MIm][Cl]. Herein, we have clearly demonstrated that the type of anion has a crucial impact on the polymerization mechanism, kinetics, and properties of produced materials.

Development of Cycloaliphatic Epoxy-POSS Nanocomposite Matrices with Lambas Enhanced Resistance to Atomic Oxygen

The preparation of ultra-thin CFRP laminates, which incorporate a cycloaliphatic epoxy resin reinforced with polyhedral oligomeric silsesquioxane (POSS) reagent nanofiller, using out-of-autoclave procedure is reported. The influence of the amount of POSS within the laminate on the mechanical properties and surface roughness of the laminates is analysed before and after exposure to atomic oxygen (AO) to simulate the effects of low Earth orbit (LEO). The addition of 5 wt% POSS to the base epoxy leads to an increase in both flexural strength and modulus, but these values begin to fall as the POSS content rises, possibly due to issues with agglomeration. The addition of POSS offers improved resistance against AO degradation with the laminates containing 20 wt% POSS demonstrating the lowest erosion yield (1.67 × 10-24 cm2/atom) after the equivalent of a period of 12 months in a simulated LEO environment. Exposure to AO promotes the formation of a silicon-rich coating layer on the surface of the laminate, which in turn reduces roughness and increases stiffness, as evidenced by measurements of flexural properties and spectral data after exposure.