Amide-Functionalized Ionic Liquids As Curing Agents for Epoxy Resin: Preparation, Characterization, and Curing Behaviors with TDE-85

Thin, Uniform, and Highly Packed Multifunctional Structural Carbon Fiber Composite Battery Lamina Informed by Solid Polymer Electrolyte Cure Kinetics

Multifunctional structural batteries promise advancements in structural energy storage technologies by seamlessly integrating load-bearing and energy-storage functions within a single material, reducing weight, and enhancing safety. Yet, commercialization faces challenges in materials processing, assembly, and design optimization. Here, we report a systematic approach to develop a carbon fiber (CF)-based structural battery impregnated with epoxy-based solid polymer electrolyte (SPE) via robust vacuum-assisted compression molding (VACM). Informed by cure kinetics, SPE processing enhances the multifunctional performance with no fillers or additives. The thin flexible CF-based laminae impregnated under high pressure achieved a substantial enhancement of ∼160% in the fiber volume fraction (FVF) as although thin and strip-shaped, the fibers were optimally packed with low void. A CF/SPE-based battery was fabricated, with a hybrid layered ionic liquid (IL)/ carbonate electrolyte (CE) showing enhanced safety and multifunctional performance. Enhanced by thin, uniform, and stiff CF-based composites, this study propels the development of advanced multifunctional structures, thereby expediting sustainable commercialization.

Conducting Composite Polymer-Based Solid-State Electrolyte with High Ion Conductivity via Amorphous Condensed Structure and Multiple Li+ Transport Channels

Traditional PEO electrolyte has high crystallinity which hinders the transmission of Li+, resulting in poor ion conductivity and complicated processing technology. Herein, a polymer electrolyte (p-electrolyte) with a wide electrochemical window and high ionic conductivity is designed, which possesses an amorphous condensed structure. The amorphous structure provides fast transport channels for Li+, so the p-electrolyte possesses an electrochemical window of 4.2 V, and high ionic conductivity of 1.58 × 10-5 S cm-1 at room temperature, which is 1-2 orders of magnitude higher than that of traditional PEO electrolyte. By using the designed polymer electrolyte as the foundation, an in situ curable composite polymer electrolyte (CPE-L) with multiple Li+ transport channels is elaborately constructed. The Cu-BTC MOF stores abundant Li+, which is introduced into the p-electrolyte. The rich unsaturated Cu2+ coordination sites of Cu-BTC can anchor TFSI- to release Li+, and the pore structure of Cu-BTC MOF cooperates with LLZTO nanoparticles to provide multiple fast transport channel for Li+, resulting in remarkable ionic conductivity (1.02 × 10-3 S cm-1) and Li+ transference number (0.58). The Li||CPE-L||Li symmetric battery cycles stably for more than 700 h at 0.1 mA cm-2, while the specific capacity of full battery is ≈153 mAh g-1 (RT, 0.2 C).

Injecting Sustainability into Epoxy-Based Composite Materials by Using Bio-Binder from Hydrothermal Liquefaction Processing of Microalgae

We report a transformative epoxy system with a microalgae-derived bio-binder from hydrothermal liquefaction processing (HTL). The obtained bio-binder not only served as a curing agent for conventional epoxy resin (e.g., EPON 862), but also acted as a modifying agent to enhance the thermal and mechanical properties of the conventional epoxy resin. This game-changing epoxy/bio-binder system outperformed the conventional epoxy/hardener system in thermal stability and mechanical properties. Compared to the commercial EPON 862/EPIKURE W epoxy product, our epoxy/bio-binder system (35 wt.% bio-binder addition with respect to the epoxy) increased the temperature of 60% weight loss from 394 °C to 428 °C and the temperature of maximum decomposition rate from 382 °C to 413 °C, while the tensile, flexural, and impact performance of the cured epoxy improved in all cases by up to 64%. Our research could significantly impact the USD 38.2 billion global market of the epoxy-related industry by not only providing better thermal and mechanical performance of epoxy-based composite materials, but also simultaneously reducing the carbon footprint from the epoxy industry and relieving waste epoxy pollution.

1-Methyl-4-R-1,2,4-triazolium (R = -CH2CH2OCH3, -CH2COOCH2CH3)-Based Ionic Liquids as Plasticizers for Solid Propellants

In this paper, a series of energetic ionic liquid plasticizers of 1-methyl-4-methoxyethyl-1,2,4-triazolium chloride (1), 1-methyl-4-methoxyethyl-1,2,4-triazolium bis(trifluoromethylsulfonyl)imide (1a), 1-methyl-4-methoxyethyl-1,2,4-triazolium nitrate (1b), 1-methyl-4-ethyl acetate-1,2,4-triazolium chloride (2), 1-methyl-4-ethyl acetate-1,2,4-triazolium bis(trifluoromethylsulfonyl)imide (2a), and 1-methyl-4-ethyl acetate-1,2,4-triazolium nitrate (2b) were synthesized and characterized. The results show that compounds 1a, 1b, 2a, and 2b have lower melting points (T_m, -72.60 to -32.67 °C) and good thermal stability (T_d, 161-348 °C) and are suitable as plasticizers for hydroxyl-terminated polybutadiene (HTPB) curing systems. Among these four ionic liquids, ester-functionalized cations can help to improve the tensile strength (2a, 0.943 MPa; 2b, 1.113 MPa) of the cured system, while ether-functionalized cations are more beneficial to improve elongation at break (1a, 522.90%; 1b, 484.45%). Ester-functionalized ionic liquids are more beneficial to reduce the glass transition temperature of HTPB elastomers. The storage modulus of HTPB elastomers containing NO₃^- is higher, while that of HTPB elastomers containing NTf₂^- is lower. The crosslink densities of HTPB/TDI/2a and HTPB/TDI/2b plasticized by ester-functionalized ionic liquids are larger, which are 9369 and 9616 mol/m³, respectively. There are hydrogen bond interactions between the ionic liquid and the HTPB elastomer, and these interactions changed the distribution of the hard and soft segments in the polymer molecules.

Thiourea modified low molecular polyamide as a novel room temperature curing agent for epoxy resin

A thiourea modified low molecular weight polyamide (TLMPA) as a room temperature curing agent was synthesized by a two-step method. Firstly, a low molecular weight polyamide curing agent (LMPA) with low viscosity and high amine value was synthesized by amidation of sebacic acid with tetraethylenepentamine, then the synthesized curing agent was modified with thiourea to increase its reactivity at room temperature. The optimal reaction conditions were studied by L9(33) orthogonal experiments. The structure of the prepared curing agent was analyzed by Fourier transform infrared spectroscopy (FT-IR). The kinetics of TLMPA curing of E-51 epoxy resin was analyzed using the Kissinger method with non-isothermal differential scanning calorimetry (DSC). The activation energy of TLMPA/E-51 calculated by the Kissinger method and FWO method was 38.79 kJ mol-1 and 42.73 kJ mol-1. The nano-SiO2 filler was compounded with E-51 epoxy resin, TLMPA, allyl glycidyl ether diluent, and KH-560 coupling agent to prepare the room temperature curing epoxy resin (EP) system. L9(34) orthogonal experiments were carried out to study the effect of various factors on the mechanical properties of the cured resin systems. The best formulation of the system is that the content of nano-SiO2, curing agent, diluent, and coupling agent is 3, 35, 15, 1 wt%, respectively. With the optimal formulation, the tensile and shear strength, tensile strength, impact strength, and bending strength of the cured EP system was 13.19 MPa, 53.8 MPa, 52.16 kJ m-2, and 94.95 MPa, respectively.