Highest Limiting Oxygen Index Value Research Articles

Small change, big impact: Simply tailoring the substitution position towards significant improvement of flame retardancy

The use of conventional flame-retardant elements such as Cl, Br, P for carbon-based polymers usually leads to the deterioration of smoke and toxic gas release, and possesses serious environmental and ecological issues. Herein, we proposed a facile strategy to largely improve the flame-retardant efficiency of an eco-friendly flame-retardant method. By simply tailoring the substitution position of the functional polymerization monomer, the corresponding copolymer exhibited extremely high flame retardancy, including a 59% lower peak heat release rate (pHRR), a 48% lower smoke density, a high limiting oxygen index (LOI) of 30%, and passed the UL-94 V-0 rating without dripping. More importantly, the para-substitution copolymer showed a much higher flame-retardant efficiency than the meta-substitution copolymer, for which the monomer content needed for UL-94 V-0 rating, high LOI value, and low smoke and toxic gas release largely decreased by 25%. The detailed mechanism and the different performance between the two copolymers were comprehensively investigated. The results first confirmed the “end-group-capturing” mechanism, then revealed that the different flame-retardant efficiency was owing to the different thermal rearrangement capability of the two functional monomers. The molecular-level mechanism revealed here provided a novel thinking for designing flame-retardant polymers.

INFLUENCE OF CARBON FIBER ON THE COMBUSTION BEHAVIOR, THERMAL STABILITY AND MECHANICAL PROPERTIES OF ETHYLENE-VINYL ACETATE COPOLYMER (EVA) AND 9,10-DIHYDRO-9-OXA-10-PHOSPHAPHENANTHRENE-10-OXIDE (DOPO) COMPOSITES

Ethylene-vinyl acetate copolymer (EVA) is widely used due to its good processability, low density, and low temperature resistance. However, it burns easily and has several disadvantages, such as a high heat release rate and melt dripping, and it emits large amounts of smog and toxic harmful gases. These disadvantages greatly limit the application of EVA in the wire and cable field. In this study, a series of carbon fiber (CF)/9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)/EVA composites are prepared through melt compounding to improve the flame retardancy and mechanical properties of EVA. The flame retardancy, thermal stability, and mechanical properties of the composites are studied through microscale combustion calorimeter experiments, cone calorimeter tests, thermogravimetric analysis, digital camera, and tensile measurements. Results indicate that among the six samples, the EVA-5 composite with 4.0 wt% CF, 16.0 wt% DOPO, and 80 wt% EVA has the highest limiting oxygen index value (25.1%) and reaches the V-1 level of the Underwriters Laboratory-94 test. Compare with that of pure EVA, the peak heat release rate of the EVA-5 composite has reduced by 30.2% and 47.7%. In addition, the total heat release of EVA-5 reduces by 17.0% and 34.8% relative to that of pure EVA. Data of thermogravimetric analysis show that the thermal stability of CF/DOPO/EVA improves with the increase in CF loading. Moreover, the tensile strength and elongation-at-break values of EVA-5 are 14.30 MPa and 1142.87%, respectively, indicating that this material can maintain good mechanical properties. CF not only enhances the tensile properties of EVA but also acts as a skeleton during burning. This action could increase the strength of the carbon layer and enhance the flame-retardant effect of DOPO. CF and DOPO have an enhanced synergistic effect that could improve the flame retardancy, thermal stability, and mechanical properties of EVA composites. This work provides a theoretical basis for the preparation and production of CF/DOPO/EVA composites with good comprehensive performance. Keywords: thylene-vinyl acetate copolymer; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; carbon fiber; flame retardant; synergistic effects

Coordination driven layer‐by‐layer deposition technology used for fabrication of flame retardant polyamide 66 fabric

AbstractPhytic acid (IP6) as the major phosphorus‐containing component of certain plants, such as cereal, oil plant, and bean possesses strong capability of coordinating with metal ion to form complex salt. In this study, low concentration IP6 was utilized in combination with Al3+ ion to in situ form insoluble Al3+‐IP6 complex salt on the surface of the fabric through coordination driven layer‐by‐layer deposition technology without high temperature cure step, which is an attempt to provide a facile bio‐based flame retardant finishing to polyamide (PA) 66 fabric. Surface structure of the treated PA fabric has been analyzed via ATR‐FTIR and SEM characterization. Effect of BLs' number on the flame retardancy and burning behavior of the treated sample has been examined by the limiting oxygen index (LOI) test, the vertical burning test, microcalorimetry, and thermogravimetric analysis. The results show that 20LBL PA fabric has the highest LOI value, highest residual char yield, and lowest THR value in all the samples and no melt dripping behavior could be detected during combustion of 20LBL PA fabric. Moreover, the insolubility of Al3+‐IP6 salt from the surface could promote the durability of the treated fabric after laundering procedure using water single. This is the first time to use coordination driven layer‐by‐layer deposition technology in the fabric's flame retardant finishing.

Simple and green synthesis of calcium alginate/AgCl nanocomposites with low-smoke flame-retardant and antimicrobial properties.

Fire hazards and infectious diseases result in great threats to public safety and human health, thus developing multi-functional materials to deal with these issues is critical and yet has remained challenging to date. In this work, we report a facile and eco-friendly synthetic approach for the preparation of calcium alginate/silver chloride (CA/AgCl) nanocomposites with dual functions of excellent flame-retardant and antibacterial activity. Multi characterization techniques and antibacterial assays were performed to investigate the flame-retardant and antibacterial properties of the CA/AgCl nanocomposites. The obtained results show that the CA/AgCl nanocomposites exhibited much higher limiting oxygen index value (> 60%) than that of CA (48%) with a UL-94 rating of V-0. Moreover, CA/AgCl particularly displayed an efficiently smoke-suppressive feature by achieving a total smoke release value of 2.7 m2/m2, which was reduced by 91%, compared to CA. The antibacterial rates of the CA/AgCl nanocomposites against E. coli and S. aureus were measured to be 99.67% and 99.77%, respectively, while CA showed quite weak antibacterial rates. In addition, the flame-retardant and antibacterial mechanisms were analyzed and proposed based on the experimental data. This study provides a novel nanocomposite material with both flame-retardant and antibacterial properties which show promising application prospects in the fields of decorative materials and textile industry.

Effects of Maleic Anhydride Grafted Polypropylene on the Physical, Mechanical and Flammability Properties of Wood-flour/Polypropylene/Ammonium Polyphosphate Composites

In this study, maleic anhydride grafted polypropylene (MAPP) was incorporated as coupling agent in the wood-flour/polypropylene/ammonium polyphosphate composites (flame-retardant WPCs). The effects of MAPP content (5 wt.%, 10 wt.% and 15 wt.%) on the physical, mechanical and flammability properties of flame-retardant WPCs were investigated. The water soaking tests showed that the incorporation of MAPP could reduce the hygroscopicity of flame-retardant WPCs. The mechanical properties of WPCs were evaluated by three-point bending tests, unnotched Izod impact strength tests, and dynamic mechanical analysis. The results showed that the flame-retardant WPC containing 10 wt.% MAPP (WPC/APP/MAPP-10 %) performed the best flexural properties, the highest impact strength, E′ value, and tan δ at room temperature. The limiting oxygen index (LOI) tests and cone calorimetry tests showed that the incorporation of 10 wt.% MAPP endowed the flame-retardant WPC with the highest LOI value, the lowest peak-heat release rate, total heat release, CO/CO2 weight ratio and total smoke release. Moreover, the characterization of the WPCs combustion residues performed that WPC/APP/MAPP-10 % had the most complete carbonaceous structure with the highest graphitization degree after combustion. In general, the addition of 10 wt.% MAPP could impart the flame-retardant WPC with the optimum physical-mechanical properties and flame-retardant performance.

A novel efficient nonflammable coating containing g-C3N4 and intumescent flame retardant fabricated via layer-by-layer assembly on cotton fiber

Flame retardant is essential for cotton fabric because of the restrictions in applications caused by poor flammability. Herein, a novel flame-retardant coating assembled on the surface of cotton fabric consists of polyethyleneimine/g-C3N4 and polyethyleneimine/phytic acid as the underlying insulating coating and the upper intumescent coating, respectively. Different amounts of the composite coatings were deposited onto the fabric by the layer-by-layer self-assembled technique. The char residue of TGA over 20 wt% has indicated the significantly enhanced performance of the thermal stability of all the coated samples and the achievement of the samples with composite coatings in a self-extinguished level proving through vertical combustion test. The samples prepared with binary hybrid coatings exhibited a high limiting oxygen index value of 30.5%. From the MCC test, the peak heat release rate and total heat release of (P/G + P/PA)4+4 showed a significant decrease of 76.9% and 77.1%, respectively. All these results demonstrated that the composite coatings endowed the cotton fabric with outstanding thermal stability and flame retardancy.

Synthesis and characterization of flame-retardant rigid polyurethane foams derived from gutter oil biodiesel

In this study, gutter oil biodiesel-based polyols (GOBP) and a reactive-type flame retardant named diethyl bis(2-hydroxyethyl)-aminomethylphosphonate (BHAPE) were both synthesized. Subsequently, gutter oil biodiesel-based flame-retardant rigid polyurethane foams (BPUFs) were prepared with GOBP, BHAPE, aluminum hydroxide (an additive-type flame retardant) and polymeric diphenylmethane diisocyanate. The properties of the BPUFs, including density, thermal conductivity, compressive properties, chemical component, morphology, thermal stability, limiting oxygen index, cone calorimetry testing, char residues stability were characterized. Among them, BPUF-AB owning 6.97 wt% of GOBP, 18.59 wt% of BHAPE and 39.77 wt% of aluminum hydroxide obtained a lower density of 0.097 g/cm3, a lower thermal conduction of 0.048 W/(m * k) and the highest compressive strength of 187 ± 13 kPa. Fire testing revealed a highest limiting oxygen index value of 30.1% and passed the UL-94 standard test. Cone calorimetry testing revealed that the peak heat release rate and peak smoke production release of BPUF-AB were reduced by 51.08% and 57.10%, respectively. Meanwhile, the total heat release rate and total smoke production were respectively decreased by 36.88% and 40.79%. The results indicate that BPUFs derived from gutter oil biodiesel are prosperously potential biomaterials with good thermal stability for fire insulation porous materials in future architecture applications.

A phosphaphenanthrene-containing vanillin derivative as co-curing agent for flame-retardant and antibacterial epoxy thermoset

A phosphaphenanthrene-containing vanillin-derived compound (VDG) was synthesized by a one-pot nucleophilic addition reaction from vanillin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and 3,5‐diamino‐1,2,4‐triazole. The molecular structure of VDG was characterized by Fourier transform infrared (FTIR), and 1H, 13C, and 31P nuclear magnetic resonance (NMR) spectrometer. Various loadings of VDG were incorporated into diglycidyl ether of bisphenol A (DGEBA) as a co-curing agent together with 4, 4′-diaminodiphenylmethane (DDM) to produce an epoxy thermoset. The thermomechanical, thermal and fire-retardant properties of EP thermosets were evaluated by dynamic mechanical analyzer (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94, and cone calorimetry. The results showed that a linear decrease in glass transition temperature with increasing loading of VDG owing to the declined cross-linking density. The cured DGEBA/DDM system with 2.0 wt% of VDG exhibited super anti-flammability in terms of a high LOI value of 37.0% and UL-94 V-0 rating, whereas the cured DGEBA/DDM and DGEBA/DDM with 2.0 wt% of DOPO systems showed no rating in UL-94 test. In addition, cone calorimetry test showed that the cured DGEBA/DDM system with 2.0 wt% of VDG exhibited a reduction of up to 47.5% and 34% for peak heat release rate and total heat release, respectively, compared to the cured DGEBA/DDM system. The enhanced flame-retardant property was attributed to the formation of the compact and continual structure of char layer residue with good thermo-oxidative stability. In addition to good anti-flammability, the cured DGEBA/DDM/VDG thermoset showed antibacterial property against E. coli, with an inhibition zone diameter of 10 mm. Thus, this bio-based co-curing agent could impart flame-retardant and antibacterial performance to epoxy for developing high performance functional thermosetting materials.

In‐situ synthesis and adhesion method to prepare phosphorous–nitrogen compounds flame‐retardant wood pulp paper with high efficiency and durability

SummaryIn the present work, flame‐retardant wood pulp paper (WPP) with high water resistance was fabricated through in‐situ synthesis and adhesion of flame retardant on the lignocellulose fibers. Through a simple solution spraying method, melamine (Me) and polyphosphoric acid solution were adequately permeated into interior lignocellulose fibers of WPP in turn and then reacted to produce water‐insoluble phosphorous–nitrogen melamine polyphosphate (MPP). The finally sprayed melamine formaldehyde prepolymer played the roles of flame‐retardant coating, adhesive agent, and water‐proofing layer, thus bonding MPP particles to the lignocellulose fibers firmly. This low‐cost and efficient treatment endowed WPP with excellent flame retardance and satisfactory durability. It showed that the modified WPP had a high limiting oxygen index value of 37.3%, and achieved B‐0 rating in vertical burning test, as well as greatly lowered the peak heat release rate and the total heat release. The flame‐retardant mechanisms of the modified WPP were analyzed and discussed. Moreover, the flame retardance kept well after 72 hours of water resistance test, showing good combination between the flame‐retardant particles and the lignocellulose fibers.

Synergistic effects of organically modified montmorillonite in combination with metal oxides on the fire safety enhancement of intumescent flame‐retarded epoxy resins

AbstractSynergistic effects of organically modified montmorillonite (OMMT) in combination with different metal oxides (Bi2O3, Sb2O3, and MoO3) on the fire safety enhancement of the intumescent flame‐retarded epoxy resins (EPs) were systematically evaluated. The results from X‐ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that the OMMT and metal oxides acquire a uniform distribution in the EP matrix, and OMMT platelets exhibit a fully exfoliated state. The flammability and thermogravimetry (TG) tests show that the intumescent flame retardant (IFR)‐OMMT‐metal oxide ternary system can endow EPs with the higher synergistic efficiencies on the enhancement of flame retardancy, smoke suppression properties, and charring ability compared to those of IFR or IFR‐OMMT system, and the synergistic efficiency is the following order: IFR/OMMT/Sb2O3 > IFR/OMMT/MoO3 > IFR/OMMT/Bi2O3. In particular, the sample, filled with 1.5 wt% OMMT, 1.5 wt% Sb2O3, and 27 wt% IFR, passes the UL94 V‐0 rating and acquires the highest limiting oxygen index value of 28.5% among the samples. The IFR‐OMMT‐metal oxide ternary system exerts a better synergistic effect on the generation of crosslinking and aromatic structures that supply the excellent charring effect and barrier effect for the EPs, and the synergistic efficiency of IFR‐OMMT‐metal oxide ternary system is varied with the types of metal oxides.

Heat-Resistant Carbon Fiber Reinforced Plastics Based on a Copolymer of Bisphthalonitriles and Bisbenzonitrile

New phthalonitrile resins that provide processing properties at the level of epoxy resins and composites obtained from them are discussed. The processing parameters of the resins are improved due to the discovery of reactive diluents based on bisbenzonitriles. By introducing these comonomers into the resin composition the melt viscosity is reduced to less than 100 MPa s at a temperature of 120°C, which allows one to obtain carbon fibers by modern injection techniques. The curing programs of the composite are selected in order to attain the maximum compressive strength (852 MPa). Carbon fiber reinforced plastics postcured at 375°C retain up to 90% of their mechanical properties at 400°C (τ12 = 60–80 MPa). It is first shown that prepregs can be produced from phthalonitrile resins using the melt technology and composites from them can be obtained by hot pressing. Carbon fibers possess high limiting oxygen index values (LOI > 80%). Thus, phthalonitrile resins and prepregs are developed for non-autoclave processing of carbon and glass composites suitable for operation at elevated temperatures.

Surface engineering of magnesium hydroxide via bioinspired iron-loaded polydopamine as green and efficient strategy to epoxy composites with improved flame retardancy and reduced smoke release

Functionalized magnesium hydroxide (MDH@Fe-PDA) by polydopamine (PDA) and iron chloride (FeCl3) were designed by one-pot method, aiming at improving flame retardancy and reducing smoke release of epoxy resin. The structure of MDH@Fe-PDA was confirmed via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). MDH and MDH@Fe-PDA with different ratio were introduced into epoxy resin (EP) as flame retardant additives. The enhanced flame retardancy and smoke suppression of EP composites were evaluated by limiting oxygen index (LOI), UL-94 test and cone calorimetry. The resultant EP composites exhibited remarkably reduced flammability, reflected by high LOI value of 29.3%, V-0 rating, as well as a 57% reduction of peak heat release rate for 7 wt% MDH@Fe-PDA loading. In addition, EP/MDH/MDH@Fe-PDA composites decreased the evolution of volatiles significantly. The char structure of EP composites revealed that char with a more intact and continuous structure. A probable mechanism was proposed which involved catalytic charring behavior at the interface and intensive protection by char and strong radical scavenging activity. Notably, this work provided an attractive method to organo-modified MDH, and enriched its practical applications of MDH as functional fillers to polymers.

Phosphorus-based flame retardant poly (butylene terephthalate): Synthesis, flame retardancy and thermal behavior

The synthesis of a flame retardant formulation based on poly (butylene terephthalate) (FRPBT) and 3- (hydroxyphenyl phosphinyl) propanoic acid (HPPA) as phosphorous-based flame retardant, was performed in a laboratory reactor. The synergistic effect of antimony trioxide (Sb2O3) and titanium dioxide (TiO2), as co-additives in combination with HPPA in FRPBT samples, was studied concerning the intrinsic viscosity (IV) and flame retardancy. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize the produced polymers. The synthesized samples were analyzed by gel permeation chromatography (GPC) to elucidate the molecular weights and their distributions. Thermal properties, thermal stability, and mechanical properties were evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing, respectively. The flame retardancy of FRPBT was examined through cone calorimeter measurements, limiting oxygen index (LOI), and UL-941 tests. The characterization results for PBT and FRPBT showed that the modification of PBT with low levels of HPPA comonomer (3 mol%) increased LOI to 31% and improved UL-94 to V-1 rating. By insertion of HPPA into the copolyester chains, the crystallinity and melting point temperature (Tm) of the polymers plus their mechanical properties were lowered. The results suggest that presence of TiO2 and Sb2O3 along with HPPA exhibits flame retardancy synergistic effects in FRPBT and increase LOI to 33% and 34.8% for PBHT and PBHS, respectively, in comparison to neat PBT (22.5%). TGA and cone calorimeter results also confirmed the same synergistic effects. A reduction was observed in the maximum mass loss rate (Rmax) and maximum decompositions temperature (Tmax) in TGA thermograms for FRPBTs in presence of 3 mol % HPPA alone and along with 3–5 mol% of co-additives, compared to PBT. Also, the results of cone calorimeter test showed that the heat release rate (HRR), peak heat release rate (PHRR) and total heat release rate (THR) of the FRPBT samples were clearly reduced. These showed that using HPPA and HPPA/co-additive compounds promoted and improved the thermal degrading and flame retardation behavior of PBT. Also, co-additives in the range of 3–5 mol% provided excellent flame retardancy in FRPBT using minimum amounts of HPPA led to high LOI values and a V-0 rating in UL-94.

Cardanol derived P, Si and N based precursors to develop flame retardant phenolic foam

A novel eco-friendly halogen-free cardanol-based flame retardant with P, Si, and N on the chain backbone (PSNCFR) was synthesized and incorporated into phenolic foams (PFs). PSNCFR was comprehensively investigated via Fourier transform infrared spectroscopy and nuclear magnetic resonance. PSNCFR endowed PFs with flame retardancy, contributed to generating a composite char defense against flames, and efficiently prevented smoking from PFs. PSNCFR introduction improved the flexural strength of the PFs to approximately 155% of that of pristine PF. PSNCFR-modified PFs displayed a high limiting oxygen index value of 41.9%. The results of cone calorimeter show that the mean heat release rate, mean effective heat of combustion, and total heat release of the PSNCFR-modified PFs reduced by 26.92%, 35.71%, and 31.25%, respectively. In particular, the total smoke production of the PSNCFR-modified PFs decreased by 64.55%, indicating excellent smoke inhibition. As for the mechanism, the condensation and gas phases during pyrolysis were responsible for the synergistic flame retardancy in the modified PFs. The findings demonstrate that PSNCFR can be used in PF preparation to overcome their drawbacks of internal brittleness and flammability.

Green Highly Clay-Filled Polyethylene Composites as Coating Materials for Cable Industry-A New Application Route of Non-Organophilised Natural Montmorillonites in Polymeric Materials.

In order to develop flame retardant and relatively green cable coating materials, polyethylene (PE) was melt blended with 5, 7.5, or 10 wt. % of a natural calcium montmorillonite (C–Ca) pre-dispersed in EBA (ethylene-butyl acrylate copolymer), EVA (ethylene-vinyl acetate copolymer), or mEVA (EVA modified with maleic anhydride). For comparison, an organophilised montmorillonite (CW9) was tested. The main study of composites containing EBA/C–Ca, EVA/C–Ca, and mEVA/CW9 pre-dispersions revealed that both clays were not fully exfoliated in the matrix, however, C–Ca (7.5 wt. %) markedly increased limited oxygen index (LOI) from 18% O2 (PE) up to 22.0% O2. An insignificantly higher LOI value (22.2% O2) was noted for a sample with 10 wt. % of CW9. The fillers did not affect hardness, but spectacularly increased Young’s modulus of the compression-moulded samples (tensile strength and elongation at break values were reduced). Thermal features of the matrix were not unpredictably changed by the clays. Generally, all the tests revealed that PE filled with the chemically untreated natural C–Ca reached similar or better mechanical and thermal features than materials containing the ammonium salt-modified montmorillonite.

Novel soluble and heat-resistant polyamides derived from 4-(4-diphenylphosphino) phenyl-2,6-bis(4-aminophenyl)pyridine and various aromatic dicarboxylic acids

New diamine, 4-(4-diphenylphosphino)phenyl-2,6-bis(4-aminophenyl)pyridine, was prepared, and the related polyamides (PAs) bearing 2,6-diphenylpyridyl units and pendant diphenylphosphinophenyl groups were synthesized by direct polycondensation of this diamine and various aromatic diacids in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The resulting PAs with inherent viscosities of 0.78–1.06 dL g−1 are readily soluble in polar aprotic solvents such as NMP, N, N-dimethylacetamide, and dimethylsulfoxide as well as less polar solvents such as m-cresol and pyridine. All the PAs are amorphous and could be solution-cast into transparent, flexible, and tough films, which have tensile strengths of 68.2–88.8 MPa, tensile moduli of 1.9–2.4 GPa, and elongations at break of 5.4–10.3%. These polymer films also exhibit high optical transparence with the UV cutoff wavelength in the 361–412 nm range. These PAs display glass transition temperatures of 316–332°C, 10% mass loss temperatures of 524–553°C, and more than 48% residues at 800°C in nitrogen, respectively. Their high char yields and good limited oxygen index values ranging from 39 to 44 indicate the prepared PAs show good thermal stability and flame-retardant property.

Reduced fire hazards of expandable polystyrene building materials via intumescent flame-retardant coatings

Despite great advances, fire safety is a permanent challenge in expanded polystyrene (EPS) foam specially used as the thermal insulating external wall in buildings and constructions. Herein, an effective flame-retardant architecture consisting of phenolic epoxy resin (PER), ammonium polyphosphate (APP) and tannic acid functionalized graphene (TGE) was successfully fabricated and coated on the surface of EPS foam plate (EPS/ATG) to achieve excellent flame retardancy and thermally insulating properties. This surface coating is equivalent to protective “shield” for expanded polystyrene foam plate. The PER/APP/TGE paintcoat with a ratio of 20:20:0.65 imparted superior fire safety to EPS foam, exhibiting a high limiting oxygen index value of 35.50%, and a UL-94 V-0 classification was achieved with only 300 um of flame-retardant layer thickness. Cone calorimeter test results showed that EPS/ATG20 foam plate was more efficient in decreasing the peak heat release rate by 53.8% and prolonging ignition time by 75.7 times in comparison with the EPS foam plate. Thermal conductivity of the EPS/ATG20 foam plate just increased from 0.048 W/m K of EPS foam plate to 0.053 W/m K. The PER/APP/TGE paintcoat not only endowed excellent flame retardancy to EPS/ATG foam plates, but maintained desirable thermal insulation properties.

Synthesis of a novel nonflammable eugenol-based phosphazene epoxy resin with unique burned intumescent char

Developing bioresourced epoxy resin with excellent flame retardancy is challenging for satisfying environmental and fire hazard requirements. Herein, a novel monomer with six functional epoxy groups was successfully synthesized by combining eugenol with hexachlorocyclotriphosphazene. Using aliphatic diamine as a curing agent, a novel epoxy of EHPE-D230 was prepared, and its properties were systematically evaluated. Compared with commercial epoxy resin (E51-D230), EHEP-D230 possessed a higher tensile strength (56.7 to 64.2 MPa) and better thermal resistance (Tα = 85 to 119 °C). Moreover, EHEP-D230 exhibited a high limiting oxygen index value of 31%, and it passed the UL94 V-0 test without any after-flame time. Cone calorimeter test indicated that the peak value of the heat release rate, total heat release, and total smoke production for EHEP-D230 reduced significantly by 66%, 65%, and 78%, respectively, compared with those of E51-D230. The EHEP-D230 residual char exhibited a compact and continuous exterior structure and a honeycomb-like hollow vesicle interior structure. This unique intumescent char endowed EHEP-D230 with excellent flame retardancy and smoke suppression, rendering it a potential candidate for fire-resistant applications.

New poly(aryl ether ketone)s containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups

4-(4-Diphenylphosphino)phenyl-2,6-bis(4-hydroxyphenyl)pyridine, as a new bisphenol monomer, was prepared from 4-(diphenylphosphino)benzaldehyde and 4-hydroxyacetophenone and used in the preparation of several aromatic poly(ether ketone)s (PEKs) containing 2,6-diphenylpyridyl units and diphenylphosphinophenyl pendant groups via a nucleophilic aromatic substitution polycondensation with difluorinated aromatic ketones. The polycondensation proceeded quantitatively in tetramethylene sulfone in the presence of anhydrous potassium carbonate and afforded the polymers with high molecular weights. The resulting PEKs are amorphous and exhibit high glass transition temperatures of 209–255°C and 5% weight loss temperatures of 536–554°C with char yields of 57–62% at 800°C in nitrogen. Their high char yields and good limited oxygen index values ranging from 39 to 43 indicated these polymers exhibited good thermal stability and flame-retardant property. All new PEKs were soluble in common organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and chloroform and could form tough, flexible, and strong films with tensile strengths of 74.6–86.8 MPa, tensile moduli of 2.9–3.6 GPa, and elongations at break of 5–9%.

Synergistic Fire Hazard Effect of a Multifunctional Flame Retardant in Building Insulation Expandable Polystyrene through a Simple Surface-Coating Method.

This work reports a strategy based on γ-aminopropyltriethoxysilane (KH550) and graphene oxide (GO)-functionalized 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to fabricate P–N–Si integrated flame retardant [KDOPO-modified GO (DGO)] through mild Mannich and Silanization reactions to overcome the challenge of single gas-phase fire retardancy of DOPO. DGO-based phenolic epoxy resin (DGO/PER) is manufactured and coated on the surface of expandable polystyrene (EPS) foam plates to achieve fire safety, which is used as the thermally insulating external wall in buildings and constructions. The DGO/PER paintcoat imparts high fire safety to the EPS foam plate, exhibiting a high limiting oxygen index value of 29%, and a UL-94 V-0 classification is achieved with only 300 μm of layer thickness compared with the DOPO/PER paintcoat. Meanwhile, all combustion parameters such as peak heat release rate, heat release rate, total heat release, smoke release rate, total smoke rate, and ignition time present excellent promotions for EPS@DGO compared with EPS@DOPO. These dramatically reduced fire hazards are mainly attributed to the synergistic effects of DGO. Meanwhile, the DGO/PER flame-retardant paintcoat cannot deteriorate the thermal insulation performance of the EPS foam plate.