High-performance Epoxy Composites Research Articles

Innovative upcycling cigarette filters into high-performance cellulose nanofiber-epoxy composites

This research introduces a novel upcycling method for transforming cigarette filters—an abundant and persistent environmental waste—into high-performance epoxy composites reinforced with cellulose nanofibers. The innovation lies in extracting cellulose acetate nanofibers from used cigarette butts via a multi-step purification and electrospinning process, followed by their conversion into regenerated cellulose nanofibers through alkaline hydrolysis. This dual-fiber approach allows us to fabricate four distinct epoxy composites, each reinforced by different nanofiber types: recycled cellulose acetate nanofibers, regenerated cellulose nanofibers from recycled cigarette filters, and their commercial counterparts. Notably, this is the first time regenerated nanofibers derived from waste cigarette filters have been utilized for epoxy composite reinforcement, demonstrating a sustainable, high-value use for a major pollutant. Comprehensive characterizations, including FTIR, XRD, SEM, and contact angle measurements, confirmed the successful regeneration of cellulose nanofibers, showing improved hydrophilicity, reduced crystallinity, and uniform nanofiber morphology with diameters between 200 and 300 nm. The innovation further extends to the mechanical performance of these composites: tensile tests revealed that those reinforced with regenerated cellulose nanofibers exhibited superior tensile strength (49.5–53.8 MPa), significantly outperforming both cellulose acetate nanofiber composites (40.1–42.6 MPa) and neat epoxy resin (31.4 MPa). This marked improvement is attributed to enhanced nanofiber dispersion and interfacial adhesion within the epoxy matrix, an essential advancement over traditional composites. In addition, thermal analysis showed that all composites maintained thermal stability in the 300–400 °C range, comparable to commercial alternatives. The regenerated nanofiber-reinforced composites also displayed enhanced optical transparency due to reduced light scattering, making them ideal candidates for applications requiring both mechanical strength and optical clarity. By pioneering the use of cigarette filter waste for fabricating advanced cellulose nanofiber composites, this study presents an eco-friendly approach to addressing environmental pollution while creating sustainable materials with superior mechanical, thermal, and optical properties.

Functional cellulose-derived epoxy cross-linked with BADGE resin to construct high-performance epoxy composites

The development of equipped bio-based epoxy materials has been gaining much attention recently. Nevertheless, finding the balance between the structure and properties of materials remains a significant challenge. In this work, cellulose-based epoxy (PHPCEP) with “soft” and “hard” cooperative structures was designed and demonstrated to endow bisphenol A diglycidyl ether (BADGE) with excellent toughness, heat resistance, mechanical strength, glass transition temperature, thermal stability, and solvent resistance. When 5 wt% PHPCEP was incorporated into BADGE composites, the resulting materials exhibited the maximum flexural strength (121.9 MPa) and tensile strength (71.4 MPa), a high glass transition temperature (148.3 °C), and 10 wt% PHPCEP/BADGE demonstrated the highest impact strength (70.5 kJ/m2). These figures are 18.8 %, 16.1 %, 21.5 %, and 254.3 % higher than the corresponding values of neat BADGE. The results of dynamic mechanical properties and heat degradation of the cured specimens also suggest that PHPCEP/BADGE materials have superior stiffness and toughness than neat BADGE, which could be attributed to the strong interaction between PHPCEP and BADGE, delivering better thermal stability for the composites compared to the pristine resin. Considering the remarkable effect, this work provides an effective way of highly efficient utilization of abundant cellulose and a high-performance additive for composite materials.

Bridging solvent-free polyamic acid and epoxy resin by Si-O-C hyperbranched polymer for enhanced compatibility, toughness and self-lubrication performance

Despite the great application potential of epoxy resin (EP) modified with polyamic acid (PAA), the large amount of high-boiling-point non-protonic polar solvents used to promote their compatibility cannot be completely eliminated, which affects the fabrication and application of epoxy composites in practical engineering. Herein, PAA was prepared by solvent-free ball milling method, and then the primary amine hyperbranched polysiloxane (HSiNH2) was prepared by “one-pot” method as the “bridging structure” to improve the compatibility between PAA and EP. Compared to neat EP, the flexural, impact and tensile shear strength of the epoxy composite are increased by 22.2 %, 30.0 % and 23.2 %, while the average friction coefficient and volume wear rate are reduced by 26.5% and 20.6% under the contents of PAA and HSiNH2 are 1.50 wt% and 2.0 wt%, respectively. Moreover, the material exhibits excellent thermal properties. By comprehensively analyzing the structure and properties of the epoxy composite, it is mainly ascribed to the fact that HSiNH2 with a large number of reactive groups acted as a “bridging structure” to enhance the compatibility of PAA and EP, which results in the epoxy composite having excellent mechanical, tribological and thermal properties. This research also lays the theoretical foundation for the development of high-performance epoxy composites in aerospace.

High performance epoxy composites modified by a ladder-like polysilsesquioxane

Developing transparent epoxy resins (EPs) with high mechanical properties, thermally stable, and superior dielectric properties is of vital importance for electronics and communication application. Here we synthesized a novel ladder-like polysilsesquioxane containing phenyl and amino groups (N-PPSQ) via a facile co-condensation process for EP modification. The N-PPSQ features a highly regular ladder-like structure with several reactive amino groups anchored, as confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nuclear magnetic resonance silicon spectroscopy (29Si NMR). Different EP/N-PPSQ composites with optimized additive contents were prepared. Compared to the pure EP, 10 wt% N-PPSQ addition helps to increase the impact strength of EP by a maximal 73 % while simultaneously improving the tensile and flexural properties. With maintained high transparency and enhanced hygrothermal stability, the EP/N-PPSQ composite shows lower dielectric constant and dielectric loss than pure EP. The work demos a fine solution to improving the toughness, dielectric properties and hygrothermal stability without sacrificing the mechanical and optical properties of EP.

Enhanced Thermal Conductivity of Epoxy Composites Fabricated with Boron Nitride and Multi-Walled Carbon Nanotubes

Preparation of polymer-based packaging materials with rapid heat dissipation capacity is crucial for ensuring high-power equipment’s service life. To achieve this, boron nitride (BN) and multi-walled carbon nanotubes (MWCNTs) were used in different ratios to prepare thermally conductive epoxy composites. These composites were created through a simple mixing and curing process, resulting in a heat transmission path. Then, BN and MWCNTs were separately functionalized with dopamine and acid to enhance their dispersibility and interfacial compatibility within the epoxy resin. This was done to further explore their influence on the formation of serial heat transfer pathways. The BN/MWCNTs/epoxy composites with a filler ratio of 15:1 and a total filler loading of 30 wt % exhibited a thermal conductivity of 0.92 W/mK, which is 118% higher than pure epoxy. These composites also displayed favorable mechanical properties and thermal stability. This study provides guidance for designing high-performance epoxy composites to meet modern electronic devices’ thermal management requirements.

High Performance Epoxy Composites Containing Nanofiller Modified by Plasma Bubbles.

The thermal conductivity of polymer materials is a fundamental parameter in the field of high-voltage electrical insulation. When the operating frequency and power for electrical equipment or electronic devices increase significantly, the internal heat will increase dramatically, and the accumulation of heat will further lead to insulation failure and serious damage of the whole system. The addition of filler with high thermal conductivity into polymer is a common solution. However, the interfacial thermal resistance between filler and bulk materials is the major obstacle to improve thermal conductivity. Herein, in order to reduce the interfacial thermal resistance, nanofillers are modified by plasma technology. The surface modification of nano-Al2O3 is carried out using plasma bubbles with three atmospheres (Ar, Ar+O2, air) as well as coupling agent. The situation of surface grafting before and after the modification is characterized using FTIR, XPS, and SEM. The effect of the mechanism of modification on the thermal conductivity and reaction pathway is investigated. The results showed that the thermal conductivity after plasma modification is increased significantly. Especially, the thermal conductivity is increased by 35% for the sample modified by Ar+O2 atmosphere. This results because more hydroxyl is introduced on the filler surface by the plasma bubbles, which enhance the interface compatibility between filler and epoxy. In addition, surface insulation performance for the modified samples also is enhanced by 14%. This is associated with the change of surface resistance and trap distribution. These results provide potential support for the development of fabrication for high performance epoxy composites.

Flame retardancy and wear resistance of epoxy composites modified by whisker-shaped nickel phyllosilicate and microencapsulated ammonium polyphosphate.

Whisker-shaped nickel phyllosilicate (NiPS) was synthesized using rod-like nickel-based metal-organic frameworks as the hard templates, and highly efficient flame retardant and wear resistant EP composites were prepared by synergizing with microencapsulated ammonium polyphosphate (MFAPP). The research results indicated that at a total addition amount of 8 wt% and a mass ratio of 2 : 5 for NiPS to MFAPP, the limiting oxygen index of the EP composite was 28.2%, which achieved the V-0 rating in the UL-94 standard. Meanwhile, the peak of heat release rate and total heat release was reduced by 33.9% and 22%, respectively, compared with pure EP. The synergistic system of NiPS and MFAPP promoted the formation of high-quality char layer, preventing the diffusion of heat, oxygen, and combustible gases effectively during combustion of the EP composite. Dry friction test showed that the wear rate of the EP composite was 0.847 × 10-5 mm3 N-1 m-1, which was 87.9% lower than pure EP, indicating a significant improvement in wear resistance. This study provided a promising method for the preparation of high performance epoxy composites with excellent flame retardancy and wear resistance.

Carbon nanotube-vertical edge rich graphene hybrid sponge as multifunctional reinforcements for high performance epoxy composites

Thermal management materials with excellent electromagnetic interference (EMI) shielding performance have attracted research interest in the field of modern electronic devices. Herein, vertical edge rich graphene (VG) was in-situ grafted on the carbon nanotube (CNT) sponge to create connective 3D hybridized carbon skeleton with covalent bonding, then CNT-VG/epoxy composites were constructed to meet the needs of multifunctional application. Impressively, mainly owing to the connectivity of 3D CNT sponge, the conduction ability of interfaces and the defect-rich structure of VG, the obtained CNT-VG/epoxy composites possessed an enhanced EMI shielding effectiveness of 46.9 dB with a thickness of 1 mm and an improved thermal conductivity of 2.23 W m−1 K−1 which contributes to superior thermal management capability. In addition, the excellent structural design also increases the flexural strength by 349.39% compared to pure epoxy resin, achieving a flexural strength of 275.32 MPa and a work of fracture of 9956.98 kJ m−3. The novel multifunctional CNT-VG/epoxy composites with enhanced mechanical property show a bright application prospect in next-generation electronic devices.

Interfacial engineering of epoxy/silica nanocomposites by amino-rich polyethyleneimine towards simultaneously enhanced rheological and thermal-mechanical performance for electronic packaging application

As electronic devices move toward miniaturization and high-degree integration, it becomes imperative to use nano-sized silica as a reinforcing filler for epoxy resin in modern electronics packaging industries. However, the use of silica nanoparticles (SNPs) brings about new challenges in filler dispersion and in the balance between the rheology and thermal mechanical performance of epoxy nanocomposites. This study presents a novel strategy aiming to address the above challenges by interface engineering with amino-rich branched polyethyleneimine (PEI) polymer molecules through a facile self-assembly process. This not only enables a considerable decrease (by 79.7%) in viscosity accompanied by a significant improvement in viscosity stability (only 2.7 times increase after 24 h) but also leads to a further CTE reduction of 4.8 ppm/°C (equivalent to the effects of around 10 wt% SNPs) relative to the SNPs. This work offers a new direction and efficient approach to develop high-performance epoxy composites for electrical packaging applications as well as provides some fresh insights into the interface-property relationships.

Facile construction of lamellar-like phosphorus-based triazole-zinc complex for high-performance epoxy resins

Epoxy resins (EP) possessing superior flame retardancy, mechanical properties and glass transition temperature are urgently needed to meet the ever-increasing requirement of high performance for the practical application of EP. Herein, lamellar-like phosphorus-based triazole-zinc complex (Zn-PT) was firstly constructed through coordination reaction in a facile condition to address the above issue. The results revealed that Zn-PT was well dispersed in epoxy matrix, and with 3 wt% Zn-PT, the tensile strength, flexural strength and modulus of epoxy composites were remarkably increased from 71, 112 and 2982 MPa of neat epoxy resin (EP) to 80, 162 and 3482 MPa respectively. The glass transition temperature was higher than EP. Besides, the limiting oxygen index (LOI) increased to 28.3%, and UL-94V-1 level was available. Meanwhile, the cone calorimeter test (CCT) results showed that epoxy composites displayed less heat release and smoke production. Generally, this work provides a feasible strategy to prepare high-performance epoxy composites, which has the potential to satisfy the requirement of epoxy in the practical application.

Thermal stability and gamma ray shielding properties of tungsten borides/epoxy micro-composites

Particle reinforced epoxy matrix composites have recently been intensively prepared and investigated in numerous publications as a promising alternative gamma ray shielding materials. In this work, a DDM (4,4′-diaminodiphenylmethene) hardener modified by AA (acrylic acid) was used to cure the epoxy resin (E51) at room temperature. To obtain high performance epoxy composites, 30% by weight of tungsten borides WB and WB2 microparticles treated with a KH-560 silane coupling agent were incorporated into the epoxy matrix (EP0) and the composites were coded as EP30WB and EP30WB2, respectively. SEM (scanning electron microscopy) analysis confirmed the good dispersion of these fillers within the polymeric matrix. The structure of the synthesized epoxy matrix and its related composites were characterized using the FTIR (Fourier transform infrared) analysis. According to the FTIR spectra, the epoxy matrix as well as the micro-composites were effectively cured in less than 4 h. This rapid curing process can be justified by the reaction of the epoxy and acrylamide groups as well as the strong reactivity of DDM with AA. The thermal stability of the samples was evaluated by DSC (differential scanning calorimetry) and TGA (thermal gravimetric analysis). DSC analysis revealed that EP30WB2 has a high exothermic peak (166.68 °C) compared to EP30WB (154.48 °C). In addition, the TGA analysis showed that T5% (temperature of 5% weight loss) increased from 207.01 °C for EP0 to 339.65 °C for EP30WB and 346.92 °C for EP30WB2. Meanwhile, the char yield (Yc) at 800 °C has increased from 23.85% for EP0 to 40.36% for EP30WB and 45.99% for EP30WB2, respectively. Moreover, using a Cs-137 radioactive source, the linear and mass attenuation coefficients (μ, μm), half-value layer (HVL), ten-value layer (TVL) and radiation protection efficiency (RPE) for the epoxy matrix EP0, EP30WB and EP30WB2 micro-composites were experimentally determined. The shielding efficiency for EP0 was 17% and it was improved to 32% and 35% by filling EP0 matrix with WB and WB2, respectively.

Combination of cardanol-derived flame retardant with SiO2@MOF particles for simultaneously enhancing the toughness, anti-flammability and smoke suppression of epoxy thermosets

In this work, an organic-inorganic flame retardant composite system was utilized by combining the renewable cardanol-based flame-retardant toughening agent (CF-PO(OPh)2) and the core-shell SiO2@MOF particles, then a series of high-performance epoxy composites with simultaneously enhanced mechanical properties, fire safety as well as smoke suppression effect were prepared with incorporating different ratio of the organic and inorganic flame retardant components. The epoxy composite containing 3% CF-PO(OPh)2 and 2% SiO2@UiO-66 (EP3) showed the most striking enhancements in the mechanical and flame retardant performances. The tensile strength and impact strength of EP3 was 48.8% and 25.3% higher than those of EP0, respectively. In view of flame retardant properties, EP3 showed maximum reductions in PHRR, SPR, CO, and CO2 productions which were 30.5%, 25.8%, 51.4%, and 43.7% lower than those of EP0, respectively. The excellent flame retardant and mechanical properties of epoxy composites resulted from the synergetic effect of cardanol-based phosphorus-containing CF-PO(OPh)2 and inorganic core-shell SiO2@UiO-66 particles.

Phosphoric acid derived efficient reclaimation of carbon fibre for re-manufacturing high performance epoxy composites reinforced by highly-aligned mat with optimized layup

This study presented an economic and closed-loop recycling approach of carbon fibre reinforced polymers (CFRP) comprising phosphoric acid derived efficient reclaimation of recycled CF (rCF) and re-manufacture of high performance epoxy (EP) composites reinforced by highly-aligned rCF mat. The integral rCF with clean surface and intact graphitization structure showed the high retention ratios of 97.1 and 99.5% in tensile strength and modulus, respectively, as well as highly-aligned arrangement of rCF mat with preferential alignment degree (PAD) of 83.5% much contributed to increasing its maximum volume fraction up to ~ 40% in composites. Thus, through fully utilizing the property anisotropy and structural designability of aligned rCF, mechanical and EMI shielding performance of rCF/EP composites were significantly enhanced via optimizing mat layup configurations.

Surface functionalization of carbon fabric towards high-performance epoxy composites via enhanced fiber–matrix interfacial strength and intergrowth charring behavior

Surface functionalization of carbon fabric towards high-performance epoxy composites via enhanced fiber–matrix interfacial strength and intergrowth charring behavior

A cast-in-place fabrication of high performance epoxy composites cured in an in-situ synthesized 3D foam of nanofibers

A cast-in-place process is usually adopted to prepare bicontinuous composites which display good mechanical properties and excellent comprehensive performance. But the construction of an intercommunicating porous skeleton seems to be cumbersome and low efficient. Here we report a three-dimensional nanofibers foam (3D NFF), which has been fabricated and applied to enhance epoxy resin composite. The 3D NFF skeletons with densities from 0.028 to 0.218 g/cm3 were fabricated by regulating the conditions for the nanofiber growth. The 3D NFFs were conveniently modified with a silane coupling agent to improve the interface interaction with the epoxy matrix. Compared to the pure epoxy, the compressive strength of the cast-in-place processed 3D NFFs/epoxy composite was improved by 436.8% at loading of 3.9 wt%, and the flexural strength was increased by 133.5% at loading of 5.3 wt%. While the compressive and flexural strength of the NFPs/epoxy composite prepared through traditional mixing method was increased by 173.6% at loading of 3.9 wt%, and 63.1% at loading of 5.3 wt%, respectively.

Preparation and Thermomechanical Properties of Ketone Mesogenic Liquid Crystalline Epoxy Resin Composites with Functionalized Boron Nitride.

In order to enhance the thermomechanical behaviors of epoxy molding compounds, the hexagonal boron nitride (h-BN) fillers were incorporated in a ketone mesogenic liquid crystalline epoxy (K–LCE) matrix to prepare a high-performance epoxy composites. The h-BN was modified by surface coupling agent 3-aminopropyltriethoxysilane (APTES). The grafting of silane molecules onto the surface of BN fillers improved the compatibility and homogeneous dispersion state of BN fillers in the K–LCE matrix with a strong interface interaction. The surface-modified BN fillers were characterized using Fourier transform infrared spectroscopy. The thermomechanical properties and morphologies of K–LCE/BN composites loading with different contents of modified BN fillers, ranging from 0.50 to 5.00 wt%, were investigated. These results show that modified BN fillers uniformly dispersed in K–LCE matrix, contributing to the enhancement in storage modulus, glass transition temperatures, impact strength and reduction in the coefficient of thermal expansion (CTE). The thermal stability and char yield of the K–LCE/BN composites were increased by increasing the amount of modified BN fillers and the thermal decomposition temperatures of composites were over 370 °C. The thermal conductivity of the K–LCE/BN composites was up to 0.6 W/m·K, for LC epoxy filled with 5.00-wt%-modified BN fillers. Furthermore, the K–LCE/BN composites have excellent thermal and mechanical properties compared to those of the DGEBA/BN composites.

Recyclable High Performance Epoxy Composites Based on Double Dynamic Carbon–Nitrogen and Disulfide Bonds

Recycling of the thermosetting resin is a big challenge due to the formation of cross-linked, three-dimensional network structures after curing. In this study, a simple mild and effective method wa...

Nano-BN encapsulated micro-AlN as fillers for epoxy composites with high thermal conductivity and sufficient dielectric breakdown strength

In this work, the nano boron nitride (BN) was modified by poly(dopamine) and micro aluminium nitride (AlN) was modified by y-(2,3-epoxypropoxy)propytrimethoxysilane. Then the nano-BN was anchored though the chemical bonding reaction onto the surface of micro-AlN. The epoxy composites with the BN encapsulated AlN hybrid filler were prepared, showing a enhanced thermal conductivity of 1.449 W/(m-k), which is 946% higher than that of EP, 0.153 W/(m-k). And the results of dielectric breakdown experiments in high voltage at high frequency show that the sufficient dielectric strength with breakdown time of 72.6s, which is 256% higher than that of EP, 28.33s. This work provides a facile method for preparing high-performance epoxy composites with high thermal conductivity and sufficient dielectric breakdown strength.

High performance epoxy composites prepared using recycled short carbon fiber with enhanced dispersibility and interfacial bonding through polydopamine surface-modification

The critical issue and challenge in reusing recycled carbon fiber (rCF) was to fully exerting its outstanding properties via an efficient and environmental-friendly way. In this study, the strengthening effects of polydopamine surface-modified recycled short CF (pDop-rSCF) on mechanical, thermo-mechanical, electrical and electromagnetic properties of epoxy (EP)-based composites were systematically evaluated. The dispersibility of pDop-rSCF in suspension used for fabricating nonwoven mat was quantitatively characterized with crowding factor N, dispersion coefficient β and fractal dimension D. Significant enhancements were achieved in tensile and flexural properties, interlaminar shear strength, storage modulus and electromagnetic interference shielding capability of EP composites reinforced with pDop-rSCF nonwoven mat, which was primarily ascribed to chemically strengthened interfacial bonding between pDop-rSCF and EP matrix and the increased connectivity among pDop-rSCFs with excellent dispersion.

Renewable vanillin-based flame retardant toughening agent with ultra-low phosphorus loading for the fabrication of high-performance epoxy thermoset

The poor impact toughness and flame retardant performance have greatly restricted the engineering application of epoxy thermoset. To obtain the high-performance epoxy composites, the renewable vanillin-based flame retardant toughening agent (PVSi) was synthesized and incorporated into epoxy. The use of PVSi macromolecules can significantly enhance the impact toughness of epoxy. With 5 wt% of PVSi, the impact strength of the epoxy was maximally raised by 189.69%, from 12.42 kJ/m2 of the neat EP to 35.98 kJ/m2 of EP/PVSi5 composites. The toughening effect of PVSi macromolecules on epoxy was closely linked to its structural features, such as the flexible phenylsiloxane, active imine and polar phosphaphenanthrene groups. Simultaneously, the EP/PVSi5 composites reached up to the V-0 rating in vertical burning test (UL-94) and 29.5% in limiting oxygen index (LOI), with only 0.27 wt% ultra-low phosphorus loading. Additionally, the suppressed heat release, the evidently reduced toxic pyrolytic volatiles, and the promoted charring capability of EP/PVSi composites can be obtained, with phosphaphenanthrene, phenylsiloxane and diaminodiphenylsulfone groups in PVSi macromolecules jointly playing a role. These results indicated the improved fire safety of epoxy. Furthermore, the free radical scavenging effect of P· and PO·, the fuel dilution effect of nonflammable NH3 and SO2, the catalytic charring effect of the pyrophosphoric acid and metaphosphoric acid, the charring-stability effect of phenylsiloxane group and the suppression effect of high-quality carbon layers were analyzed and summarized. It was expected that PVSi would pave the way for the development of more highly efficient flame retardant toughening agents and high-performance epoxy thermoset.