A chemically depolymerizable eugenol-based epoxy resin (SE-EP) containing cleavable silyl ether linkages was successfully synthesized. The SE-EP was cured with methyltetrahydrophthalic anhydride (MeTHPA) to form a cross-linked network with a cross-link density of 0.00145 molcm-3. The resulting SE-EP/MeTHPA thermoset exhibited excellent mechanical and thermal properties, including a tensile strength of 23 MPa, a modulus of 800 MPa, an elongation at break of 6.3%, and a glass transition temperature of 51 degrees C. Remarkably, in mildly acidic conditions (0.01-0.20 M HCl at 50 degrees C), the network exhibited rapid chemical depolymerization following a pseudo-first-order rate constant of k = 0.162 min-1, demonstrating a reaction rate 10,000 times faster than that of previously reported chemically depolymerizable epoxy resins. Crucially, FT-IR, 1H NMR, and GC-MS analyses confirmed the selective cleavage of the Si-O bonds and the almost quantitative recovery of the eugenol-derived materials. Specifically, 96% of the eugenol-derived monomers and 86% of the MeTHPA curing agent-derived monomers were successfully recovered. The ability to recover these monomers with such high yield and purity offers an excellent recycling method for circular resource management, as it enables the repetitive reuse of the feedstock-derived species while maintaining favorable mechanical and thermal performance in the resulting polymer, unlike conventional recycling. Therefore, the introduction of silyl ether bonds provides an effective molecular design strategy for achieving rapid chemical depolymerization and high-value circularity while maintaining the desired mechanical properties of epoxy thermosets.

Naphthalene‐modified cationic initiators with tunable counteranions were developed to extend the epoxy curing lifetime, enabling the efficient formation of high‐ordered networks in both conventional and liquid crystalline (LC) epoxy systems. The extended lifetime of these initiators allows the LC epoxies to maintain their inherently ordered structure during network formation, which is essential for efficient phonon transport. Differential scanning calorimetry demonstrated a broader exothermic peak width and a more uniform heat release profile, confirming controlled and efficient polymerization. X‐ray diffraction analysis further demonstrated that the π–π stacking peak characteristic of the LC domains was clearly preserved, indicating that the mesogenic order was maintained after curing. Consequently, the cured LC epoxies exhibited a remarkably high thermal conductivity of 0.86 W m−1 K−1. This is one of the highest reported for unfilled organic systems. Adding hexagonal boron nitride (h‐BN) filler further enhanced heat transfer, reaching 25.08 W m−1 K−1 at 85 wt%. These results demonstrate that rational initiator design with long‐term operation and controlled polymerization provides a simple strategy for fabricating high‐purity, thermally conductive, and reprocessable epoxy networks for advanced thermal management applications.

Epoxy thermosets are widely used in advanced structural and electronic applications due to their excellent mechanical, thermal, and chemical stability derived from densely cross-linked polymer networks. However, the permanent network structure of conventional thermosets makes their recycling extremely challenging, often leading to downcycling or energy-intensive recovery processes. Here, we report a biobased epoxy thermoset derived from eugenol (Eu-EP) that incorporates a high density of multicleavable urethane bonds within both the epoxy monomer and curing agent. This molecular design enables rapid and uniform depolymerization of the cross-linked network under mild alkaline conditions (1 M NaOH, 50 degrees C) without the use of catalysts. Systematic depolymerization studies demonstrate efficient chemical recycling to monomers (CRM), achieving up to 94% recovery of key molecular components, including Eu-diol, eugenol, and curing agents. The recovered monomers were successfully reused to synthesize regenerated thermosets exhibiting thermal and mechanical properties comparable to those of the original materials. Furthermore, the depolymerization chemistry was extended to carbon fiber reinforced polymer (CFRP) composites, enabling selective matrix removal while preserving the woven architecture of the carbon fiber reinforcement. These results highlight the potential of multicleavable epoxy networks as a platform for chemically recyclable thermosets and sustainable composite materials.

The use of composite materials incorporating carbon fibers (CFs) is steadily increasing. Given the high energy costs associated with manufacturing CFs, the need for recycling has become critical not only for environmental sustainability but also for economic viability. Although several recycling methods have been developed recently, there remains a significant gap in the integrated analysis of the properties of recycled CFs (r-CFs). Such an analysis is essential to maximize the usability of r-CFs recovered through various recycling techniques. Unlike previous studies that focused on individual recycling methods, this study systematically compared pyrolysis, supercritical fluid (SCF), superheated steam (SHS), and chemical oxidation under standardized conditions to elucidate direct correlations between process parameters and r-CF characteristics. Therefore, in this study, we analyzed the physical properties of r-CFs recovered through various recycling processes, focusing on surface morphology, chemical functionality, mechanical properties, and interfacial adhesion with polymer resins. The recycling processes included thermal and chemical oxidation methods, with a particular emphasis on preserving CF mechanical integrity while enhancing interfacial compatibility with polymer matrices. The organic residues and surface composition of r-CFs were analyzed through XPS, SEM, and AFM, and their electrical conductivity and tensile strength were measured. Additionally, the interfacial shear strength (IFSS) between epoxy resin/r-CFs and polyamide 6/r-CFs was evaluated. As a result, it was confirmed that chemical oxidation method was found to effectively introduce oxygen functional groups while minimizing structural degradation, thereby maintaining the mechanical and electrical properties of r-CF better than the recycling method using high temperature and high pressure. In particular, the chemical oxidation method facilitates improved interfacial adhesion with epoxy resin due to the synergy between surface roughness and chemical bonding, while its effect on PA6 adhesion is comparatively limited due to the high viscosity of the resin. These findings contribute to establishing sustainable recycling strategies for CFRP waste and advancing circular economy principles in the composites industry.

Epoxy resin (EP) composites with low cost and high flame retardancy were fabricated by incorporating powdered activated carbon (PAC) and aluminum hydroxide (ATH) as flame-retardant fillers. The composites were prepared using a conventional melt-mixing and curing process with diglycidyl ether of bisphenol A (DGEBA) and hexamethylenediamine (HMDA) as the epoxy and hardener, respectively. Flame-retardant performance was evaluated using cone calorimetry, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The EP composite containing 40 wt% PAC and 10 wt% ATH (denoted as EP/PAC40/ATH10) exhibited a 50% reduction in peak heat release rate (PHRR) from 474.4 to 239.0 kW/m2, and a 61% decrease in total heat release (THR) from 63.2 to 24.8 MJ/m2 compared to neat EP. Total smoke production (TSP) also decreased by 55%, from 16.2 to 7.3 m2. Furthermore, the char yield at 800 degrees C increased from 6.3% (neat EP) to 48.7% (EP/PAC40/ATH10), confirming improved thermal stability. The thermal conductivity of the EP/PAC40/ATH10 composite was 0.63 W/m K, more than double that of neat EP (0.21 W/m K). These results indicate that the combined use of PAC and ATH enhances the flame retardancy, smoke suppression, and heat dissipation of EP composites, providing a promising solution for fire-safe epoxy applications.

Accurate evaluation of thermal conductivity in polymeric materials is crucial for the development of advanced thermal management systems in electronics. In this study, a total of five epoxy resins imine-based epoxy (IEP), azine-based epoxy (AEP), ketone-based epoxy (KEP), double imine-based epoxy (DIEP), and acetylene-based epoxy (ACEP) were synthesized. The thermal conductivity of the cured materials under various conditions was then evaluated using the transient plane source (TPS) method. Their liquid crystalline (LC) behavior was confirmed by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), revealing nematic and smectic phases for azine-based epoxies (AEP) and imine-based epoxies (IEP), respectively. Determination of the optimal curing agent and curing temperature was achieved by analyzing the exothermic peaks obtained from dynamic DSC scans of various epoxy resin–curing agent combinations. The curing agent whose exothermic behavior overlapped with the LC temperature range of the epoxy resin was selected to prepare the cured materials. To ensure reliability, the thermal conductivity value was determined using the stabilized region of the residual graph from the TPS measurement, where the deviation of the temperature difference was at a minimum. When cured in the LC state, the thermal conductivity values were 0.36 W/m·K for IEP/diaminodiphenylmethane (DDM) and 0.35 W/m·K for AEP/DDM. Accurate thermal conductivity of LC epoxy resins was achieved by excluding unstable data regions, highlighting the importance of accurate measurement for understanding molecular ordering effects.

Water-resistant vitrimers are essential for practical applications frequently exposed to moisture, where conventional dynamic covalent networks often suffer from hydrolytic degradation. In this study, we report a waterresistant bio-based vitrimer film (WR-VF) constructed via dynamic boric ester crosslinked networks, incorporating citric acid as a multifunctional crosslinking agent. The WR-VF is synthesized from tannic acid, boric acid, glycerol, polyvinyl alcohol (PVA), and citric acid, using ethanol as the solvent to enhance hydrolytic stability. FTIR analysis confirms the formation of boric ester linkages and a dense hydrogen bonding network, which significantly limits water penetration and contributes to excellent long-term water resistance. After 25 days of water immersion, the WR-VF retains its structural integrity, with a tensile strength of 4.02 MPa and 336 % elongation, exhibiting less than 3 % performance loss. The film demonstrates outstanding elastic recovery, achieving over 92 % shape recovery after 100 % strain and maintaining performance over repeated cycles. Moreover, above the vitrimer transition temperature (Tv), the WR-VF recovers 95 % of its original tensile strength after reprocessing. It also shows chemical recyclability in ethanol at 80 degrees C, allowing the film to be re-cast with preserved properties. These results highlight the potential of citric acid-mediated boric ester networks in developing sustainable, water-resistant vitrimers for moisture-sensitive and eco-conscious applications.

As the use of carbon fiber (CF)-reinforced composites increases, recycling has become essential for both environmental sustainability and economic feasibility due to the high energy cost of CF production. This study systematically compared recycled CFs (r-CFs) obtained via pyrolysis, supercritical fluid (SCF), superheated steam (SHS), and chemical oxidation, analyzing surface morphology, chemical functionality, mechanical properties, and interfacial adhesion with polymer resins. Results showed that chemical oxidation effectively introduced oxygen functional groups while minimizing structural damage, preserving the mechanical and electrical properties of r-CFs better than high-temperature methods. Notably, it significantly enhanced interfacial adhesion with epoxy resin. These findings contribute to sustainable recycling strategies for CFRP waste.

This study introduces the possibility of using polyaniline as a thermally conductive filler in the manufacturing process of composites using epoxy. Compared to conventional thermally conductive fillers, polyaniline is a material with a simple synthesis process and is cost-effective. In this experiment, among various types of polyaniline, polyaniline in the form of an emeraldine salt (ES) doped with protons and polyaniline in the form of a dedoped neutral emeraldine base (EB) were used as the thermally conductive filler. ES doped with protons show higher electrical and thermal conductivity than EB due to the conductive polymer characteristics in which the thermal conductivity increases as the electrical conductivity increases. We put both fillers into the widely commercially available diglycidyl ether of bisphenol A (DGEBA) epoxy composite, and analyzed the effect of the thermal conductivity of the filler increased by doping on the thermal conductivity of the composite, and analyzed the possibility of use as a thermally conductive filler. The epoxy resin without filler was measured to have the thermal conductivity of 0.21 W/m K, the thermal conductivity of the composite reinforced with EB filler was measured to be 0.27 W/m K, and the thermal conductivity of the composite reinforced with ES filler was measured to be 0.29 W/m K. The results confirmed that the input of polyaniline as a thermally conductive filler could improve the thermal conductivity of the composite, and also confirmed that the proton-doped ES filler showed higher thermal conductivity than the neutral EB filler. Through this study, we highlight the possibility that polyaniline can be used as a promising thermally conductive filler for various composite materials.

Vitrimers, as dynamic covalent network polymers, represent a groundbreaking advancement in materials science. They excel in their applications, such as advanced thermal-conductivity composite materials, providing a sustainable alternative to traditional polymers. The incorporation of vitrimers into composite fillers enhances alignment and heat passway broadly, resulting in superior thermal conductivity compared to conventional thermosetting polymers. Their dynamic exchange reactions enable straightforward reprocessing, fostering the easy reuse of damaged composite materials and opening possibilities for recycling both matrix and filler components. We review an overview of the present advancements in utilizing vitrimers for highly thermally conductive composite materials.

This study aimed to address the environmental concerns associated with petrochemical-derived bisphenol-A, commonly used in epoxy resin synthesis, by developing an eco-friendly alternative utilizing bio-based ascorbic acid, or vitamin C. The epoxy compound was synthesized by leveraging the hydroxyl group inherent in ascorbic acid through a reaction with epichlorohydrin. Optimal curing conditions were determined via dynamic scan and isotherm analysis using Differential Scanning Calorimetry (DSC) for the newly synthesized epoxy resin in combination with isophorone diamine (IPDA) as the curing agent. The cured product, obtained under the identified optimal curing conditions, exhibited a soft hardened form with a tensile strength of 7.5 MPa and an elongation of 6

To achieve the best physico-chemical properties of polymer composites, the concentration of fillers should be maximized in many cases. However, at extremely high concentrations of fillers, the discontinuity of the polymer matrix results in poor mechanical properties. To overcome this problem, we propose an efficient protocol to improve the mechanical strength significantly, even at an extremely high concentration of microscale fillers (graphite flakes, 95 wt%). Since the mechanical strength of the polymer composite strongly depends on both the homogeneous distribution of the polymer matrix around microscale fillers and the adhesion between them, we increased the mechanical strength of the composite by the preparation of a hybrid filler decorated with polymer nanoparticles. The decorated polymer nanoparticles eventually turned to the matrix during hot-pressing process like a mortar between bricks. Systematic studies on the mechanical strength as well as electrical and thermal conductivities of the composites revealed that both the precisely controlled size of the polymer nanoparticles and even distribution of them on the hybrid fillers were critical variables to enhance the material 's properties above. The newly developed polymer composites with superior physical properties exhibited good electromagnetic interference shielding (EMI shielding effectiveness >80 dB in X-band, thickness similar to 1.5 mm), making them suitable as electric heaters.

We synthesized a novel curcumin-based bioepoxy resin by introducing epichlorohydrin (ECH) into the hydroxyl groups of curcumin and analyzed it using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The epoxy equivalent weight (EEW) was determined based on a reaction with sodium hydroxide (NaOH) through titration, and the actual curing process was conducted after exploring the optimal conditions using an amine-based curing agent through dynamic scanning in differential scanning calorimetry (DSC) and isotherm analysis. The cured epoxy resin had a tensile strength, Young's modulus, and glass transition temperature (Tg) of 33 MPa, 1.4 GPa, and 86 °C, respectively. Interestingly, the diunsaturated ketone contained in the epoxy resin showed on-demand chemical cleavability, in that it had been decomposed into an aldehyde and ketone only after having been converted to a hydroxyl ketone through an oxidation reaction. The results of this study can significantly contribute to improving the eco-friendliness and recyclability of epoxy resins used in fields requiring long-term stability and chemical resistance.

We report novel research results demonstrating the production of polymer nanocomposites with high thermal conductivity. The use of diluents, a conventionally used method to reduce viscosity and increase processability, had clear limitations that could not be used for solid epoxy, but in this study, the melting point of the epoxy itself was reduced through the introduction of the eutectic system, allowing the solid epoxy to be converted into a liquid phase. By utilizing eutectic liquid (EL) derived from ketone-containing epoxy resin (DBPE) and diphenylamine (DPA), we achieved maximal filler content. Unlike DBPE's solid form at 135 degrees C, EL displayed liquidity with a viscosity of 50 Pa center dot s at 50 degrees C, enabling curing with isophorone diamine (IPDA) below DBPE's melting point. While DBPE/IPDA yielded a tensile strength of 7.2 MPa due to uneven mixing, EL/IPDA reached 44.3 MPa, marking a 520 % improvement. EL's viscosity dropped dramatically, reaching 0.06 Pa center dot s at 98 degrees C. The EL/IPDA mixture's viscosity at 98 degrees C was 150 Pa center dot s, allowing up to 80 wt% hexagonal boron nitride (h-BN) filler. This led to a thermal conductivity of 16 W/m center dot K, 20 wt% higher than DGEBA's 60 wt% filling rate. Notably, EL/h-BN composites achieved 16 times the thermal conductivity of DGEBA/h-BN composites, which is 1 W/m center dot K. Lowering the melting point and viscosity expanded curing agent choices, enhanced tensile strength, increased filler content, and heightened thermal conductivity, showcasing EL's remarkable potential.

Here we report a novel chemical recycling of carbon fiber-reinforced plastic (CFRP) using meta-chloroperoxybenzoic acid (mCPBA) as the representative oxidizing agent. The optimal decomposition conditions for the epoxy (EP) resin in CFRP were investigated by varying mCPBA concentration and reaction time. The CFRP decomposed completely within 6 h using a 1.5 M mCPBA solution at 40 °C. Tensile strength of recovered CF (r-CF) measured 4.4 GPa, 93.6% of virgin CF (v-CF), and electrical conductivity reached 590 S/cm, 95% of v-CF. Furthermore, the interfacial shear strength (IFSS) of the recovered carbon fibers (r-CF) using EP resin and polyamide 6 (PA6) was analyzed. For EP resin, the IFSS of r-CF was 88 MPa, a 26 % increase compared to v-CF. In the case of PA6 resin, IFSS values were 80 MPa for r-CF, a 17% improvement over v-CF. The study highlights superior mechanical properties and favorable IFSS of r-CF, positioning them as promising for composite regeneration. Remarkably, this method operated at relatively low temperatures compared to existing technologies, with energy consumption recorded at 35 MJ/kg, establishing it as the most energy-efficient recycling method available.

Increasing environmental concerns have driven the pursuit of sustainable alternatives to petrochemical-based plastics in polymer chemistry. In this study, we demonstrated a method by which sugar, the most chemically produced biomass, can be used as a thermosetting resin. The sucrose was successfully oxidized, synthesized, and then incorporated into a resin. Sodium periodate (NaIO4) was used to convert sucrose into chemical raw materials. The resulting polymer, prepared via the imine reaction, exhibited a glass transition temperature T-g of 96 degrees C, as determined by differential scanning calorimetry. Additionally, the thermosetting resin exhibited a tensile strength of 7 MPa, a modulus of 515 MPa, and a T-g of 100 degrees C. We obtained reaction rate constants of 0.7 x 10(-3) h(-1) and 3.2 x 10(-1) h(-1) using THF and citric acid solutions, respectively. Furthermore, we reused the resin from the decomposed organic matter and confirmed that the resynthesized overall, our findings suggest the potential for green recycling by converting commonly used sugars into nature-derived raw materials, leading to the development of eco-friendly polymer synthesis.

Biovitrimer pads with high flame retardancy and high thermal conductivity were developed using tannic acid (TA), phosphoric acid (PA), and poly(vinyl alcohol) (PVA). For the first time, it was discovered that this type of thermal pad is formed through dynamic bonding of P-O-C covalent bonds. The vitrimer transition temperature (T v), which indicates dynamic covalent bonding, was controlled within the 74-91 degrees C range by adjusting the TA, PA, and PVA composition ratio. Below T v, the vitrimer exhibited excellent elastic recovery properties, with a recovery rate of over 90% when subjected to 100% strain. The material demonstrated a tensile strength of 8 MPa and 430% elongation at break. Interestingly, samples deformed at 100 degrees C (above T v) and then rapidly cooled showed a shape memory effect, returning to their original form when reheated above T v. Thanks to the phosphoric acid in the vitrimer, these materials achieved high limiting oxygen index values exceeding 55% and the highest V-0 rating in the UL-94 test, demonstrating excellent flame retardancy not seen in existing vitrimers. Combining biovitrimer and hexagonal boron nitride (h-BN) produced a composite film with a thermal conductivity of up to 3.8 W/mK, proving its effectiveness as a heat dissipation pad. Additionally, the vitrimer's properties allowed for the complete recovery of both h-BN and biovitrimer through recycling. A closed-loop recycling process demonstrated that a composite film with the same heat dissipation performance could be remanufactured using reclaimed biovitrimer and h-BN.

Vitrimers are being actively studied as sustainable plastics. To that end, robust vitrimer films fabricated from a ternary aqueous solution of tannic acid (TA), boric acid (BA), and polyvinyl alcohol (PVA) are reported herein. The trimeric vitrimer films include B-O-C dynamic covalent bonds. The optimal vitrimer film exhibits excellent crosslinking density (0.0471 mol/cm(3)), tensile strength (77 MPa), and modulus (3.2 GPa). A carbon-fiber-reinforced vitrimer (CFRV) was prepared with a vitrimer film and carbon fiber at temperatures above T v. The CFRV (tensile strength, 570 MPa; modulus, 21 GPa) can be used as a structural composite material. Additionally, it retains the unique recyclability and reprocessability of the vitrimer. The solution-cast film can be reproduced from the vitrimer solution prepared during recycling, and a CFRV similar to the original can be recreated by remolding the recovered carbon fiber with the reproduced vitrimer film. The synthesized biobased high-strength vitrimer films can facilitate the development of sustainable carbon-fiber-composite materials.

Epoxy, a typical thermosetting resin, exhibits excellent mechanical properties, thermal stability, and chemical resistance. However, it can cause environmental pollution when discarded prior to decomposition. In this study, a novel oxime epoxy based on 1,4-benzoquinone dioxime was developed. It decomposes quickly under mild conditions and without requiring organic solvents, thus is environmentally friendly. The optimal curing temperature for benzoquinone oxime epoxy (BOE) with a curing agent was 85? as determined by differential scanning calorimetry. In addition, the tensile strength and Young's modulus of the BOE/1,6-hexanediamine (HMDA) resin are 20 and 400 MPa, respectively, and T-g is 76?. Furthermore, thermogravimetric analysis revealed that the BOE resin was thermally stable. Interestingly, BOE/HMDA degraded in 8 h under mild conditions. This rapid degradation will facilitate the development of new chemically degradable epoxy molecules with embedded oximes and provide insights into solving the environmental problems caused by discarded epoxy resin.