EP Matrix Research Articles

Multi-DOPO-based derivative for enhancing flame retardancy and mechanical properties of epoxy resin

Achieving a balance between flame retardancy and overall performance in epoxy resin (EP) continues to be a significant challenge. In this study, a new multi-DOPO-based reactive flame retardant (DZH) was synthesized successfully using a simple one-pot method and employed as a co-curing agent with DDM. The results indicated that the inclusion of DZH decreased the activation energy of the curing reaction system. Furthermore, the presence of DZH, with its remarkable charring ability, enhanced the formation of char residues under high-temperature conditions. Notably, the flame retardancy and mechanical properties of the EP/DZH system were significantly enhanced at certain additions. When added at only 5 wt% (phosphorus content: 0.525 wt%), the LOI value of the EP/DZH-5 increased from 24.4 % to 35.3 % for the EP matrix and achieved a V-0 rating in accordance with UL-94. Meanwhile, EP/DZH-5 exhibited a reduction of 44.1 % in pHRR and 24.3 % in SPR. The superior flame retardancy of the EP/DZH system was attributed to the dual flame-retardant mechanism exhibited in both the gaseous and condensed phases. In addition, the abundant presence of rigid phosphaphenanthrene groups and π-π interactions between benzene rings led to an improvement in the tensile strength and tensile modulus, which rose to 91.0 MPa and 1.76 GPa, respectively, from 79.5 MPa and 1.26 GPa of EP in the case of EP/DZH-3. The utilization of this flame retardant, based on multi-DOPO, offers a promising approach for the development of high-performance epoxy resins.

Preparation of a MOF flame retardant containing phosphazene ring and its effect on the flame retardant of epoxy resin

With the aim of effectively improve the flame retardant and smoke suppression performance of epoxy resin (EP), a novel metal-organic framework (Zn-MOF) containing phosphazene ring and Zn2+ was synthesized by solicitation method. The results showed that adding 9 wt% solvent removed Zn-MOF (SR-Zn-MOF) could reduce the peak heat release rate (PHRR), the peak smoke production rate (PSPR), the peak of CO production (PCOP) and CO2 production (CO2P) of epoxy resin composites by 58.9, 45.8, 48.6, and 51.9%, respectively. Based on the analysis of the pyrolysis process of Zn-MOF and the study of the condensed phase char residues, it is found that the organic ligands containing phosphazene ring in Zn-MOF are thermally decomposed in the condensed phase to form the containing phosphoric acid and pyrophosphate substances, which together with the generated ZnO can effectively promote the carbonization of EP matrix. At the same time, the organic ligands will pyrolysis generate a large number of non-flammable gases such as NH3 and CO2, which can promote the intumescent of the char layer, and effectively dilute the concentration of combustible fuel and O2 in the gas phase. Therefore, Zn-MOF have excellent flame retardant and smoke suppression effect on EP.

0D-2D nanohybrids based on binary transitional metal oxide decorated boron nitride enabled epoxy resin efficient flame retardant coupled with enhanced thermal conductivity at ultra-low additions

Epoxy resin (EP) possesses standout traits in adhesion, electrical insulation, as well as mechanical properties, thus it is frequently concerned in the field of electronic packaging. However, EP has shortcomings of poor flame retardancy and thermal conductivity, and it is easy to induce thermal runaway in long-term service. In this work, 0D-2D nanohybrids (BN@CoFeOx) were obtained through a facile coprecipitation-thermal oxidation method, where cobalt-iron metal oxides as decorations were in situ generated on the surface of boron nitride (BN) as the substrate. Then, EP/BN@CoFeOx nanocomposites were prepared by physical blending of BN@CoFeOx and EP, pouring and curing. BN@CoFeOx nanohybrids fulfilled homogeneous dispersion in EP and strong interfacial interactions with the EP matrix. Besides, BN@CoFeOx nanohybrids imparted EP with high flame-retardant efficiency and exceeding smoke suppression properties at low additions of only 2 wt%, reflected in a 44.7%, 42.7%, 54.8%, and 56.2% decrease of the peak heat release rate (pHRR), total heat release rate (THR), peak smoke production rate (pSPR), and total smoke production (TSP) values, respectively. Furthermore, the limiting oxygen index (LOI) value increased from 24.2% of EP to 34.3%, and the vertical combustion test (UL-94) results reached a V0 rating. Meanwhile, the introduction of BN@CoFeOx nanohybrids adjusted for the formation of highly graphitized carbon layers, and boosted the thermal stability of EP. When the addition of BN@CoFeOx nanohybrids was 0.5 wt%, the peak mass loss rate (Rmax) of EP/BN@CoFeOx nanocomposites dropped by 33.6%. In addition, on account of the phonon transfer within and between nanohybrids, combined with the thermal conduction path formed by nanohybrids, BN@CoFeOx accomplished the thermal conductivity enhancement of EP. Hence, the newly designed and prepared EP/BN@CoFeOx nanocomposites provide the possibility to dissipate heat accumulation and promote the flame-retardant performance of electronic products, and consequently reduce the occurrence of thermal runaway.

Dual nucleation sites induced by ZIF-67 towards mismatch of polyphosphazene hollow sub-micron polyhedrons and nanospheres in flame retardant epoxy matrix

Polyphosphazene has drawn an abundance of attention as a flame retardant due to its eco-friendliness and phosphorus-nitrogen synergistic effect. ZIF-67 and cobalt compounds derived from cobalt ions released by ZIF-67 were employed as dual templates for loading polyphosphazene. We skillfully designed a polyphosphazene hollow hybrid material via the polymerization of phosphazene accompanied by the etching of ZIF-67 and cobalt compounds by generated HCl. The hybrid material (CPPHS) was composed of cobalt-doped polyphosphazene hollow sub-micron polyhedrons (CP) and polyphosphazene hollow nanospheres (PHNS) with different dimensions and magnitudes of sizes. After adding 2.0 wt% CPPHS, the limiting oxygen index of epoxy resin increased to 27.6%, while the peak heat release rate and total smoke production decreased by 40.1% and 38.8%, respectively.The formation of a continuous and strongly extended dense char layer in the EP composites was fostered by the synergistic effect of Co-P-N flame retardant components, significantly decreasing the heat flow and combustible gas exchange rate and effectively hindering the combustion chain reaction. Furthermore, the unique dimensional mismatch structure of CPPHS enhanced its dispersion in the EP matrix, enabling the EP to have superior mechanical properties that match realistic application requirements, consequently expanding the variety of applications for fire-resistant EP composites.

Study of Heat Treatment Effect on Mechanical Properties of Epoxy Resin Reinforced with Fiber Glass.

In this paper, mechanical properties of the diglycidyl ether of bisphenol A epoxy resin (EP) reinforced with a 20% fiber glass (GF) with layered structure after high temperature aging are studied. Tensile and flexural stress-strain curves of the GF/EP composite after aging tests in the temperature range of 85-145 °C in air were measured. Tensile and flexural strength demonstrate gradual decrease with the increase in the aging temperature. The failure mechanism at the micro scale is studied by the scanning electron microscopy. A separation of the GFs and EP matrix and evident pullout of the GFs are observed. Degradation of the mechanical properties is explained by a cross-linking and chain scission of the initial molecular structure of the composite and decrease in the interfacial adhesion force between GFs and EP matrix caused by oxidation of the EP matrix and difference of the GF and EP coefficients of thermal expansion.

Well-aligned MXene@MoS2/Carbon nanofiber aerogels reinforced epoxy composites with splendid thermal and tribological performance

Epoxy resin (EP) composites are attracting intensive interest for aviation aircraft applications due to superior machinability and high corrosion resistance. However, the poor tribological performance of EP matrix greatly limits its wide application because of highly brittle and weak thermal properties. Herein, we constructed a vine-like MXene@MoS2/Carbon nanofiber aerogel (MMoCA) via directed freezing method and cellulose carbonization treatment. The obtained MMoCA exhibited long-range-aligned 3D porous lamellar structure and the MXene@MoS2 attached to carbon nanofiber surface presented good dispersion inside the aerogel. Such a novel aerogel bestowed the EP composites with outstanding thermal properties through constructing continuous oriented thermal diffusion channels inside the EP matrix. Meanwhile MMoCA reinforced EP composites (MMoCA-EP) showed great potential in tribological application, resulting from the rapid friction heat dissipation and high-quality transfer films during the friction process. This study has a significant guidance to develop high performance polymer composites in the frontier field of tribology.

Novel epoxy/cyclic olefin copolymer/carbon structural composites with electro‐activated self‐healing properties

AbstractMultifunctional self‐healing composites have great potential in several applications, i.e., from automotive to aerospace. This study examines the self‐healing behavior of carbon fiber reinforced composites by depositing jet‐spun cyclic olefin copolymer (COC) meshes on dry carbon fiber plies before lamination with epoxy resin (EP). Three different laminates were prepared, including neat EP/CF and two composites with 4 wt.% and 8 wt.% of COC in the form of a jet‐spun network as a healing agent. The introduction of COC mesh reduced flexural stress by 26% and interlaminar shear strength by 50%. Mode I interlaminar fracture toughness (GI) was evaluated and specimens were mended at 110°C by resistive heating generated by an electrical current flowing within the samples. The laminates containing 8 wt% COC reported a healing efficiency, evaluated as the ratio between the GI and as the ratio of the maximum load (PMAX) of virgin and healed samples, of 9.4% and 33.7%, respectively. Fractography analysis highlighted the poor adhesion between the COC mesh and EP matrix, and several COC microfibers were trapped inside the epoxy matrix, hindering their diffusion inside the crack zone, which limited the healing capability of the prepared laminates.

Biomimetic construction of hierarchical MXene@PDA@CoFeOx nanohybrids towards efficient fire-safe epoxy nanocomposites with enhanced thermal conductivity and mechanical properties

Developing high-performance MXene-based polymer nanocomposites through a biomimetic method has been a research hotspot. However, it is still an intractable challenge to achieve MXene-based polymer nanocomposites with efficient fire safety, excellent thermal conductivity, and enhanced mechanical properties. Here, inspired by the adhesion of mussels, the hierarchical MXene@PDA@CoFeOx nanohybrid was fabricated by a self-assembly strategy and then employed to prepare epoxy resin (EP) nanocomposites. It has been found that MXene@PDA@CoFeOx can display excellent dispersion and interfacial compatibility in EP matrix. Thermogravimetric analysis shows that only 2.0 wt% MXene@PDA@CoFeOx results in excellent thermal stability and char yield (31.29 wt%) of EP under a nitrogen atmosphere. Combustion tests show that the 2.0 wt% MXene@PDA@CoFeOx confers efficient fire safety to EP. Remarkably, the EP-2.0%MXene@PDA@CoFeOx can obtain an attractive UL-94 rating of V0. Meanwhile, the peak heat release rate (pHRR), smoke factor (SF), and peak CO production rate (pCO) of EP-2.0%MXene@PDA@CoFeOx are dramatically decreased by 33.38%, 55.41%, and 36.84% in comparison to those of virgin EP, respectively. The efficient fire safety of EP nanocomposites is mainly attributed to the barrier effect, dilution effect, and catalytic carbonization effect of hierarchical MXene@PDA@CoFeOx. Furthermore, the MXene@PDA@CoFeOx enables EP to boast enhanced thermal conductivity (improved by 69.14%), impact strength (improved by 13.38%), and flexural strength (improved by 17.60%). This work offers a feasible biomimetic method for fabricating hierarchical MXene@PDA@CoFeOx nanohybrids and preparing efficient fire-safe EP nanocomposites with excellent thermal conductivity and mechanical performance.

Novel phosphorus-free and core–shell structured ZIF-67 for simultaneously endowing epoxy resin with excellent fire safety, corrosion and UV resistance

Two novel and eco-friendly phosphorus-free ZIF-based core–shell nanomaterials were prepared and employed to enhance fire safety of epoxy resins (EPs), which interestingly possessed both anti-corrosion and UV resistance properties. ZIF-based nanomaterials were firstly constructed by growing zinc hydroxystannate (ZHS) on surface of zeolitic imidazolate framework-67 (ZIF-67) to generate core by a simple etching method (ZIF-67@ZHS), and the sol–gel technique was then used to form shells on the surfaces (ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2). After incorporation of the prepared nanomaterials into the EP, the introduced TiO2 and SiO2 shells effectively weakened the negative impact on the EP matrix because of abundant metallic elements exposed by the ZIF-67@ZHS core. In particular, the EP composite sample (EP/5ZIF-67@ZHS@SiO2) with the addition of 5 wt% ZIF-67@ZHS@SiO2 showed a better cone calorimeter combustion test result with a 32.0 % reduction in peak heat release rate (PHRR) compared to pure EP. Additionally, the EP composites containing 5 wt% ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2 demonstrated a significant reduction in the release of toxic gases, specifically the peak CO production (COP) decreased by 17.2 % and 34.5 % relative to pure EP, respectively. Besides, both EP/5ZIF-67@ZHS@TiO2 and EP/5ZIF-67@ZHS@SiO2 coatings showed an order of magnitude improvement in impedance modulus at 0.01 Hz compared to pure EP, with EP/5ZIF-67@ZHS@SiO2 exhibiting no significant decline over 15 days. In addition, all EP composites containing modified ZIF-67 showed a decrease in UV transmittance, especially the UV transmittance of EP/5ZIF-67@ZHS@TiO2 between 350 - 400 nm decreased to below 1.8 %. This preparation strategy exhibits prominent potentials in application as a multifunctional advanced epoxy composite.

Effects of different metal ions in phosphonitrile-modified organometallic complexes on flame retardancy of epoxy resin

Two organometallic (Zn and Fe) coordination compounds, modified by phosphonitrile, were prepared by solvothermal method. The introduction of the two organometallic coordination compounds significantly improved the flame retardancy, smoke suppression and thermal stability of epoxy resins (EP). Especially, zinc-containing coordination compounds exhibited higher efficiency than iron-containing ones in flame-retardant EP. LOI values of Zn-PDH/EP and Fe-PDH/EP were further enhanced and reached up to 29.8% and 28.9%, respectively. Organometallic coordination compounds modified by phosphonitrile mainly exerted the flame-retardant action in condense phase by the combined effect of the catalysis charring effect of metal ions and flame-retardant effect of phosphonitrile, and thus a high-temperature stable graphitized carbon layer with P- and N-containing cross-linking structures formed. This high-quality carbon layer was a vital factor in improving the heat/smoke suppression properties of EP thermosets. Further, due to the weaker catalytic char-forming effect of iron ions and the formation of fewer cross-linked structures, the strength and barrier properties of the Fe-PDH/EP char layer were relatively lower than those of Zn-PDH/EP. Consequently, Zn coordination compounds presented higher efficiency in suppressing heat/smoke release of EP matrix than Fe hybrids. Finally, the gas-phase function of organometallic coordination compounds should not be overlooked due to releasing phosphorus-oxygen free radicals and N-containing fragments during pyrolysis, exhibiting flame inhibition and dilution effect in gas phase, especially for 6%Zn-PDH/EP.

LDH@Boronate Polymer Core-Shell Nanoparticles: Nanostructure Design for Synergistically Enhancing the Flame Retardancy of Epoxy Resin.

As a promising nanofiller, layered double hydroxides (LDHs) can advance the fire safety of epoxy resin (EP), but so far, due to the problems of dispersion and low efficiency, it has still been a challenge to incorporate the flame retardancy and mechanical properties of EP nanocomposites effectively under the circumstance of a low additive amount. In this work, we take LDHs as the template, via the adsorption of a catechol group and the condensation polymerization between catechol groups and phenylboric acid groups, to prepare a core-shell structured nanoparticle LDH@BP, which contains rich flame-retardant elements. EP/LDH@BP nanocomposites were prepared by introducing LDH@BP into EP. The experimental results indicate that, compared with the original LDH, LDH@BP disperses uniformly in the EP matrix, and the flame retardancy and mechanical properties of EP/LDH@BP are significantly improved. At a relatively low content (5 wt%), EP/LDH@BP reached the rating of V-0 in the UL-94 test, LOI was increased to 29.1%, and peak heat release rate (PHRR) was reduced by 35.9% in cone calorimeter tests, which effectively inhibited the release of heat and toxic smoke during the combustion process of EP. Simultaneously, the mechanical properties of EP/LDH@BP have been improved satisfactorily. The above results derive from the reasonable architectural design of organic-inorganic nano-hybrid flame retardants and provide a novel method for the construction of efficient and balanced EP nanocomposite system with LDHs.

Facile Construction of Inorganic Phosphorus/Boron-Layered Double Hydroxide Complexes for Highly Efficient Fire-Safety Epoxy Resin

For inorganic flame retardants, facile fabrication and high-efficiency fire safety without compromising the mechanical property of the matrix are still significant challenges. Here, nanolayered double hydroxide containing boron constructed on the surface of ammonium polyphosphate (APP) complexes (B-LDH@APP) is prepared by a simple in situ coprecipitation technology to reduce the fire hazard and improves the mechanical performances of epoxy resin (EP). The as-obtained 4B-LDH@APP/EP achieves the UL-94 V-0 rating and presents superior flame-safety performance. With respect to the 4APP/EP, the fire growth rate (FIGRA), the peak heat release rate (pHRR), and the peak smoke production rate (pSPR) of 4B-LDH@APP/EP decrease by 77.8, 57.3, and 52.6%, respectively. This is mainly attributed to the excellent synergistic flame-retardant effect among boron, LDH, and APP, which can accelerate the generation of compact charring residual with a good microstructure during combustion of B-LDH@APP/EP composites. Furthermore, B-LDH@APP slightly affects the mechanical performances of the EP matrix due to the upgraded interfacial interaction.

In‐situ formation of macromolecule P/N/Si flame retardant for epoxy resin with low smoke toxicity and excellent flame‐retardancy

AbstractEpoxy resins (EP) have great chemical and physical properties, but their poor flame retardant properties have prevented their widespread use. To improve the flame retardancy properties of EP, an active P/N/Si flame retardant (KDC) containing a double bond was successfully synthesized in this work by using a typical aldehyde amine condensation reaction. This flame retardant not only can form a large molecule flame retardant in situ by double bond reaction and increase the tightness with EP matrix, but also has the advantage of P/N/Si three elements synergistic flame retardant, and at the same time play the flame retardant performance of each element, can achieve excellent flame retardant performance and low smoke and toxicity with low addition amount. Subsequently, the performance of the flame retardants was tested. When 7 wt% of KDC was added, the pHRR and TSR of the EP composites were reduced by 51.7% and 29.8%, respectively. More importantly, the addition of KDC inhibited the release of toxic fuels and smoke from EP, where the TSP values of EP/3‐KDC were 18.14% below those of neat EP and increased the residual amount of charcoal, while the inhibition of CO and CO2 release was particularly pronounced with the presence of KDC.

Effect of Layered Aminovanadic Oxalate Phosphate on Flame Retardancy of Epoxy Resin.

To alleviate the fire hazard of epoxy resin (EP), layered ammonium vanadium oxalate-phosphate (AVOPh) with the structural formula of (NH4)2[VO(HPO4)]2(C2O4)·5H2O is synthesized using the hydrothermal method and mixed into an EP matrix to prepare EP/AVOPh composites. The thermogravimetric analysis (TGA) results show that AVOPh exhibits a similar thermal decomposition temperature to EP, which is suitable for flame retardancy for EP. The incorporation of AVOPh nanosheets greatly improves the thermal stability and residual yield of EP/AVOPh composites at high temperatures. The residue of pure EP is 15.3% at 700 °C. In comparison, the residue of EP/AVOPh composites is increased to 23.0% with 8 wt% AVOPh loading. Simultaneously, EP/6 wt% AVOPh composites reach UL-94 V1 rating (t1 + t2 =16 s) and LOI value of 32.8%. The improved flame retardancy of EP/ AVOPh composites is also proven by the cone calorimeter test (CCT). The results of CCT of EP/8 wt% AVOPh composites show that the peak heat release rate (PHHR), total smoke production (TSP), peak of CO production (PCOP), and peak of CO2 production (PCO2P) decrease by 32.7%, 20.4%, 37.1%, and 33.3% compared with those of EP, respectively. This can be attributed to the lamellar barrier, gas phase quenching effect of phosphorus-containing volatiles, the catalytic charring effect of transition metal vanadium, and the synergistic decomposition of oxalic acid structure and charring effect of phosphorus phase, which can insulate heat and inhibit smoke release. Based on the experimental data, AVOPh is expected to serve as a new high-efficiency flame retardant for EP.

Multi-element organic-inorganic flame retardants for enhancing the flame retardancy, reducing smoke and toxicity of epoxy resins

Epoxy resins (EP) have been commonly used, but their poor flame retardant properties have prevented their widespread use. In order to improve the flame retardant properties of EP, an organic-inorganic composite flame retardant (HKDC) containing multi-element P/N/Si was successfully synthesized in this work using a typical aldehyde amine condensation reaction. This flame retardant utilizes the synergistic effect of multiple elements to simultaneously perform the flame retardant function of each element, and it can achieve excellent flame retardant effect by using low addition amount in EP. At the same time, this flame retardant can not only reduce the migration of molecules through the structure of inorganic substances, but also the C = C reaction in EP can form large molecules and increase the compactness with the EP matrix. The flame retardants were then quantified by measuring their flame retardant properties, combustion behavior and thermal stability. When the flame retardant HKDC is added, the flame retardant performance of EP is improved and the vertical combustion test achieves a V-0 rating. Most importantly, the addition of flame retardant HKDC effectively suppressed the toxic gas and smoke emissions of EP, with TSP values much lower than those of pure EP, and CO and CO2 emissions were suppressed.

Self-Healing and Flame-Retardant Modifications of Epoxy Resins by the Diels–Alder Release-Delivery Strategy for a High-Efficiency and Green Application

The sustainability of epoxy thermosets (EPs) and EP-based composites is always limited by the evolution of internal microcracks and flammability. Herein, inspired by the drug release-delivery system for disease treatment, these symptoms of EP are solved efficiently by a multifunctional Diels–Alder (DA) release-delivery system. First, this novel system is fabricated by the cyclization reaction between the furan diene-containing phosphorus derivative and the maleimide dienophile. The resultant DA system is linked to the epoxy resin by the grafting reaction, thus ensuring its uniform dispersion. Being faced with the formation of inner microcracks, the maleimide dienophiles were released from the DA adducts under the mediated action of temperature and then were delivered to the targeted microcracks under the chemical potential difference derived from the variation of free volume. Then, the released maleimide molecules re-connect with the furan groups that existed near the microcracks to complete the repairing of the EP matrix. The skeletal structure of the EP was well preserved throughout the restoration process. Satisfactory flexural strength (105.5 MPa) and excellent crack-healing efficiency (104.5%) can be obtained for the modified EP. After three constant strain cycles, the stress retention rate can be readily maintained (more than 75%). In addition, due to the phosphorus–nitrogen synergistic flame-retardant effect from the DA system, not only the limited oxygen index of the DA-modified EP matrix can be improved to 27.5% but the lower peak release rate and lower total heat release are also observed compared with the unmodified EP.

Glass-Fiber-Reinforced 3D h-BN Skeleton for Epoxy Resin Insulation: Increased Arc-Ablation Resistance and Mechanical Strength

Epoxy resin (EP) as an insulation material is widely used in aerospace, transportation, long-distance power transmission, and other fields requiring large electrical equipment. However, the concurrent arc-ablation resistance and mechanical strength of EP have long been a bottleneck for building electrical equipment and electronic devices suitable for extreme environments, whereas existing modification technologies generally fall well short of the requirement for practical engineering applications. Herein, authors use fully exfoliated hexagonal boron nitride (h-BN) nanosheet (BNNS) and epoxy-group-grafted glass fiber (eGF) as reinforcement material to construct a 3D eGF-BNNS ordered framework via an ice-crystal-induced orientation control process. The EP/3D eGF-BNNS composite, which serves as a thermally conductive framework, is prepared by vacuum-assisted impregnation. This approach considerably enhances the ability of EP to manage large thermal loads and endows the skeleton with stronger tearing strength and tighter interfacial adhesion with the EP matrix; thus, the thermal conductivity of the EP insulation is enhanced by a factor of 19.2, the arc-ablation resistance by a factor of 3.46, and the tensile strength by 85.5%. The improvement of these properties is of great significance for optimizing the insulation of high-voltage dc circuit breaker.

Superior flame retardancy and smoke suppression of epoxy resins with zinc ferrite@polyphosphazene nanocomposites

To impart epoxy resin (EP) with excellent flame retardancy and smoke suppression, we prepared a novel inorgianic-organic nanocomposite flame retardant, zinc [email protected] ([email protected]). The inorganic zinc ferrite plays a role in catalytic carbonization, improving char yields. The organic polyphosphazene helps zinc ferrite improve its compatibility and flame retardancy. Through synergistic effects, [email protected] exhibited excellent flame-retardant and smoke-suppression properties in the EP matrix. Compared to neat EP, the limiting oxygen index of the epoxy with 5 phr [email protected] increased from 24.6% to 32.1% and reached UL94 V-0 rating; the peak heat release rate, peak smoke production rate, and carbon monoxide production of EP composites also decreased by 37%, 50%, and 39%, respectively. Condensed and gas phase analysis indicated that [email protected] helps epoxy generate more dense, stable, rigid residues and less pyrolysis volatile products, improving flame retardancy compared to ZF and PZS alone. Besides, the storage modulus of the composite was increased.

SiO2/MOFs-based synergistic flame retardants provide enhanced fire safety for epoxy resins

To improve the inherent flammability of epoxy resin (EP), a new synergistic flame retardant (SiO2/PANI/ZIF-67) with silica, polyaniline (PANI) and zeolitic imidazolate framework-67 (ZIF-67) was synthesized successfully via an electrostatic interaction and chemical bonding technique. With the addition of 6% SiO2/PANI/ZIF-67, the limiting oxygen index (LOI) of as-obtained EP composite reaches up to 28.0%. The total heat release (THR), total smoke production (TSP) and total CO production (TCOP) of the composite are significantly decreased to 44.06%, 45.05% and 44.05% respectively. The synergistic role of SiO2, PANI and ZIF-67 induces formation of a dense SiO2-C layer, which greatly reduces emission of smoke gas and heat, and subsequently increases the fire safety of EP. Furthermore, the presence of organic-inorganic hybrid ZIF-67 on surface of flame retardant leads to its strong interface adhesion and well dispersibility in EP matrix. This work provides a simple route for designing and preparation of SiO2/MOFs-based synergistic flame retardants, which is of great significance to improve fire safety of epoxy resins.

The C-S Inverse and Its Applications

In this paper, we introduce a generalized core inverse (called the C-S inverse) and give some properties and characterizations of the inverse. By applying the C-S inverse, we introduce a binary relation (denoted “ {mathop le limits ^{textcircled {S}}} ”) and a partial order (called the C-S partial order and denoted “ {mathop le limits ^{textcircled {{c!s}}}} ”), study their properties and consider the relationship between them and some classical partial orders. At last, by applying the C-S inverse, we give some characterizations of the EP matrix and i-EP matrix.