Maximum Smoke Density Research Articles

Fabrication of Functionalized Graphene Oxide-Aluminum Hypophosphite Nanohybrids for Enhanced Fire Safety Performance in Polystyrene.

To enhance the fire safety performance in polystyrene (PS), a novel organic-inorganic hybrid material (FGO-AHP) was successfully prepared by the combination of functionalized graphene oxide (FGO) and aluminum hypophosphite (AHP) via a chemical deposition method. The resulting FGO-AHP nanohybrids were incorporated into PS via a masterbatch-melt blending to produce PS/FGO-AHP nanocomposites. Scanning electron microscope images confirm the homogeneous dispersion and exfoliation state of FGO-AHP in the PS matrix. Incorporating FGO-AHP significantly improves the thermal behavior and fire safety performance of PS. By incorporating 5 wt% FGO-AHP, the maximum mass loss rate (MMLR) in air, total heat release (THR), and maximum smoke density value (Dsmax) of PS nanocomposite achieve a reduction of 53.1%, 23.4%, and 50.9%, respectively, as compared to the pure PS. In addition, thermogravimetry-Fourier transform infrared (TG-FTIR) results indicate that introducing FGO-AHP notably inhibits the evolution of volatile products from PS decomposition. Further, scanning electron microscopy (SEM), FTIR, and Raman spectroscopy were employed to investigate the char residue of PS nanocomposite samples, elaborating the flame-retardant mechanism in PS/FGO-AHP nanocomposites.

High rubber elasticity and thermal conductivity in plasticized polyvinyl chloride film with flame retardancy and smoke suppression properties

AbstractFor hydrogenated nitrile‐butadiene rubber (HNBR) modified polyvinyl chloride (PVC), magnesium hydroxide and antimony trioxide are frequently employed as flame retardants. Fume silica is thought to be useful reinforced agent for rubber as well as efficient flame retardant for polymer‐based composites. The plasticized PVC and HNBR blend in this work were combined with three fillers mentioned above to create rubber‐plastic composites that performed well overall, with a notable improvement in combustion. The limiting oxygen index of the composites increased from 23.7% to 33.8% with no droplets falling during combustion, the smoke density rating decreased from 23.8% to 7.9%, and the maximum smoke density dropped from 95.5% to 15.5%. The cone calorimetry test findings revealed that the three fillers simultaneously prevented the emission of smoke and heat from combustion. High thermal conductivity is typically linked to excellent flame retardancy. The thermal conductivity of composites rose from 0.193 to 0.583 W m−1 K−1 with the addition of fillers. Furthermore, the low glass transition temperature and permanent set of improved composites reflect its softness and rubber elasticity. Thermogravimetric analysis was used to examine the thermal stability of the composites in nitrogen and air, and the results indicated the addition of fillers improved the thermal stability.

Highly effective flame-retardant coatings consisting of urea-formaldehyde resin/aluminium hydroxide/boric acid for polystyrene foam: Properties and mechanisms investigation

The flame-retardant properties of expanded polystyrene (EPS) foam were enhanced by constructing a flame-retardant coating on its surface using melamine modified urea-formaldehyde resin (MUF), H3BO3, and Al(OH)3 as raw materials. A coating consisting of an equal proportion of H3BO3 and Al(OH)3 demonstrated superior mechanical properties, flame-retardant properties, and smoke suppression ability. Additionally, this coating increased the compressive strength of EPS material by 43.30 %, raised the carbon residue from 0.14 % to 32.4 %, elevated the limiting oxygen index to 37.4 %, and achieved a vertical combustion rating of V-0 according to UL-94 standards. These improvements were accompanied by a reduction in peak heat release rate by 59.36 %, total smoke production by 51.99 %, maximum smoke density by 80.13 %, and smoke density rating by 89.52 %. Furthermore, the coated material exhibited satisfactory water resistance, thermal insulation, and transparency. Simulation results show that the MUF/H3BO3/Al(OH)3 coating system generated various metal and non-metal compounds during combustion along with NOx, COx, and H2O gases. The beneficial flame-retardant effect of the coating can be attributed to the hybrid flame-retardant effect of H3BO3 and Al(OH)3 in both the gas and condensed phases.

Development of single-component epoxy resin with superb thermal stability, flame retardancy, smoke suppression, and latency via Cu-based phosphorus/imidazole-containing complex

To address the growing need for fire-safe single-component epoxy resin (EP) systems, this study introduced a phosphorus-containing copper complex (Cu-DA) as a multifunctional latent curing agent. The Cu-DA complex, synthesized by coordinating copper (II) chloride and a phosphorus-based imidazole, significantly improved the latency, thermal stability, and fire resistance of single-component EP. The obtained EP/Cu-DA-2 mixture with 15.3 wt% Cu-DA showed a 43-day shelf life and a rapid gel time of 22 min at 150 °C, highlighting its superb latency and fast curing. After curing, the resultant thermoset had a high glass transition temperature of 160.9 °C and increased crosslinking density, indicating superior thermal stability. The EP/Cu-DA-3 system with 17.4 wt% Cu-DA achieved a high limiting oxygen index (LOI) of 37.8 % and a UL-94 V-0 rating, reflecting its satisfactory flame retardancy. Furthermore, compared to the control EP system, the total smoke production (TSP) and maximum smoke density (MSD) of EP/Cu-DA-3 were reduced by approximately 28.4 % and 25.8 %, respectively, demonstrating significantly enhanced smoke suppression. The research offers a scalable strategy for developing single-component EP systems with rapid curing, high fire resistance, and great smoke suppression, meeting the demands of industrial applications.

High fire-safety epoxy thermosets with a macromolecular phosphorus-nitrogen containing flame retardant at a low loading

In this article, a macromolecular phosphorus-nitrogen containing flame retardant defined as PDPSB was incorporated into epoxy resins (EP). The fire safety, flame-retardant mechanism and mechanical properties of EP/PDPSB thermosets were systematically investigated. The EP-5 sheets containing 5 wt% PDPSB passed V-0 level in the vertical burning tests (UL-94) with a high limiting oxygen index (LOI) value of 30.9%. The results of cone calorimeter tests (CCT) revealed that both the emission of heat and smoke for EP/PDPSB thermosets was substantially suppressed. Compared to pure EP, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of EP-5 were dropped by 19.4%, 31.5% and 33.0%, respectively. Remarkably, the char residue mass of EP-5 was enhanced by 87.7%. The maximum smoke density (Ds, max) was slashed by 18.9%. Furthermore, the tensile, flexural and charpy impact strength of EP-5 were maintained to 97.3%, 95.1% and 86.9%, respectively. The investigation of flame-retardant mechanism demonstrated PDPSB exerted flame retardant effect both in condensed and gaseous phase by the scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectra (XPS), laser Raman spectra (LRS) and thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR). As PDPSB was a one-component multifunctional additive renowned for its exceptional efficiency, it was anticipated to facilitate the advancement of high-performance epoxy thermosets via researching on EP/PDPSB thermosets.

Effect of magnesium hydroxide fly ash compounded flame retardant on the properties of polyvinyl chloride

Abstract This study investigated the effects of compound flame retardants on polyvinyl chloride (PVC) film. Four F-M/PVC composite film materials (F0.1M0.1/PVC, F0.1M0.2/PVC, F0.1M0.3/PVC, and F0.1M0.4/PVC) were obtained by blending different ratios of fly ash (FA) and magnesium hydroxide (MH(OH)2, MH) compounded flame retardants (F-M) with PVC. The mechanical properties, thermal stability, and smoke density of the composite film materials were examined. The results showed that the loss of mechanical properties of F0.1M0.2/PVC composites was small. TGA analysis showed that the thermal stability of the four F-M/PVC composites was improved. The degradation temperature of pure PVC at T50 was 286.5°C, and that of F0.1M0.2/PVC composites was 335.38°C. Smoke density analysis showed that the maximum smoke density of pure PVC was 6.310, and the maximum smoke density of the composite material (F0.1M0.4/PVC) was reduced to 5.960, which had a better smoke suppression effect. For the comprehensive utilization of Salt Lake magnesium resources, the development of PVC composite film materials to provide the experimental basis has a strong practical value.

Unlocking anti-aging potential: Flame retardants thrive without added antioxidants

A synergistic flame retardant with a core-shell structure utilizes the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative as the outer shell and ammonium polyphosphate (APP) as the inner core. Three derivatives of DOPO (DOPO-GY, DOPO-DH and DOPO-GD) are synthesized by reacting DOPO with glyoxal, paraformaldehyde and diethanolamine, and glutaraldehyde, respectively. DOPO-GY@APP, DOPO-DH@APP and DOPO-GD@APP exhibit good radical scavenging activities. The oxidation induction time for EVA/DOPO-GY@APP is exceptionally high at 19.04 min, in contrast to EVA alone, which has an induction time of only 5.51 min. Simultaneously, after aging at 180 °C and 165 °C for 7 days, the retention rates of elongation at break for EVA/DOPO-GY@APP are 34.67 % and 55.50 %, respectively. These findings demonstrate the long-term anti-aging properties of EVA/DOPO-GY@APP without the need for additional antioxidants. Moreover, EVA/DOPO-GY@APP, EVA/DOPO-DH@APP and EVA/DOPO-GD@APP all achieve V-0 rating with 25 % addition of flame retardant. In comparison to pure EVA, their peak heat release rates and maximum smoke density decrease by 52 % and 47 %, 43 % and 54 %, and 51 % and 44 %, respectively. Additionally, compared to EVA/APP, their mechanical properties have been improved. Therefore, these microencapsulated flame retardants with DOPO derivatives as the shell effectively enhance the mechanical properties and fire safety of EVA composites.

Tailoring cross-linking temperature via hydrogen bonding and steric hindrance towards high-performance fire-Safe Polymer

Constructing thermally cross-linkable structures into thermoplastic polymers has emerged as a compelling strategy to enhance flame retardancy. However, the cross-linking reactions are hard to control, leading unexpected deterioration of processability and mechanical properties. Here, we report a novel strategy to modulate cross-linking reactions utilizing intramolecular hydrogen bonding and steric hindrance effects. Taking aromatic Schiff base (SA) as an example, novel monomers SAP and SAPN were designed and synthesized by incorporating phenolic and naphthalene units. As expected, the resultant copolymer PET-co-SAPNn exhibited a 120 °C higher cross-linking temperature compared with that of PET-co-SAn, powering them with great processability. Robust mechanical properties were obtained owing to the enhanced polymerization stability and intramolecular hydrogen bonding of SAPN, as evidenced by the tensile strength of 86.0 MPa for PET-co-SAPN15, 1.6 times to that of pure PET. Additionally, PET-co-SAPNn exhibits the highest fire safety, whose peak heat release rate (pHRR) and maximum smoke density (Dm) decreased by 49% and 53%, attributing to enhanced char-forming ability from the cross-linking and the phenolic and naphthalene units in SAPN. Considering these adequate improvements, this study provides a novel strategy for designing “self-cross-linking” flame-retardant polymers with improved processability and fire-safety.

Cage Nanofillers' Influence on Fire Hazard and Toxic Gases Emitted during Thermal Decomposition of Polyurethane Foam.

Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH3, CO and CO2. According to the literature review, complex studies on the fire hazard of a system of POSS-phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS-phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

Multifunctional Additive: A novel regulate strategy for improving mechanical property, aging life and fire safety of EVA composites

A multifunctional additive is carefully designed for crosslinked ethylene–vinyl acetate copolymer (XLEVA) composites to improve their mechanical properties, aging resistance and fire safety. In this study, first, a layer of silica was microencapsulated on magnesium hydroxide to give a large amount of hydroxyl group on the magnesium hydroxide surface; second, the primary antioxidant 3-(3, 5-di-tert-butyl-4 hydroxyphenyl) propionicacid was grafted on SiMH surface to prepare antioxidant microencapsulated flame retardants (MCMH). Compared with the pure XLEVA, the peak heat release rate and the maximum smoke density of flame retardant XLEVA/MCMH are decreased by 89.46% and 53.6%, respectively. Moreover, these oxidation induction time values of XLEVA/MH/AO and XLEVA/SiMH/AO decreased sharply after extracted for 1d. However, the OIT value of XLEVA/MCMH was basically unchanged after extracted for 5d. After aging at 165 °C for 14 days and γ-ray irradiation dose of 500 kGy, the retention of elongation at break could reach 71.8% and 86.6%, showing excellent aging resistance. These results show that MCMH has a good synergistic effect for enhancing the flame retardant, mechanical property as well as aging resistance of XLEVA composites. The “Killing three birds with one stone” strategy provides an excellent solution for obtaining high-performance XLEVA cable materials.

A novel strategy for preparing ethylene‐vinyl acetate composites with high effective flame retardant and smoke suppression performance by incorporating piperazine pyrophosphate and Ce‐MOF

AbstractCerium‐containing metal organic framework defined as Ce‐MOF was prepared and then combined with piperazine pyrophosphate (PAPP) for preparing flame retardant ethylene vinyl acetate (EVA) copolymer composites. The samples of EVA/PAPP/Ce‐MOF achieved UL‐94 V‐0 rating with the limiting oxygen index (LOI) value of 31.3% when 17 wt% PAPP/Ce‐MOF with the mass fraction of 97:3 was introduced. Under the same loading amount of PAPP, the EVA/PAPP only obtained UL‐94 V‐1 rating with the LOI value of 26.9%. Cone calorimeter test confirmed that the total heat release and total smoke production of EVA/PAPP/Ce‐MOF significantly reduced from 132.8 MJ m−2 and 11.5 m2 for EVA/PAPP to 98.8 MJ m−2 and 7.3 m2, with a reduction of 25.6% and 36.5%, respectively. Besides, the maximum smoke density decreased from 488.8 and 375.9 for EVA and EVA/PAPP to 177.5 for EVA/PAPP/Ce‐MOF. It indicated that the addition of Ce‐MOF and PAPP effectively exerted synergistic flame retardant and smoke inhibition effect for EVA. Moreover, the addition of Ce‐MOF enhanced the compatibility of PAPP with EVA matrix, and water resistance of EVA/PAPP/Ce‐MOF was higher than that of EVA/PAPP. The x‐ray photoelectron spectroscopy texts of residual char of EVA composites indicated that the cerium ion complexed with phosphoric acid and polyphosphate generated by the thermal decomposition of PAPP and then more phosphorus elements remained in condensed phase. As a result, the sufficient, crosslinking and dense char layer with excellent intensity was formed, and the heat, combustible gas and smoke were efficiently inhibited. Consequently, the EVA materials were endowed excellent fire safety as well as low heat and smoke release.

Influence of hollow glass microsphere on flame retardancy of ethylene-vinyl acetate/9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composites

To improve combustion resistance properties of EVA resin, a series of flame-retardant EVA composites were prepared by melt blending 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with hollow glass microspheres (HGM), abbreviated as EVA/HGM/DOPO. Attributable to the capture of free radicals by DOPO, the promotion of carbonation by HGM and the synergistic effects between HGM and DOPO, EVA/HGM/DOPO composites (4.0 wt% DOPO) exhibit better flame retardant performance, thermal stability, and smoke suppression performance. The limited oxygen index (LOI) results show that 4.0 wt% DOPO is replaced by HGM (EVA-5), the LOI value can be increased to the maximum value of 24.2%, and the vertical combustion reaches the V-2 level. Moreover, the peak of heat release rate (PHRR) value of sample EVA-5 was reduced by 26.5% and 42.8% in the microscale combustion calorimeter (MCC) and cone calorimeter test (CCT) compared to the pure EVA, respectively. The digital photographs and mass loss curves also give positive evidence of the synergistic condensed phase flame-retardant effects between HGM and DOPO. Particularly, the maximum smoke density (Ds, max) of EVA-5 composite is the lowest. The thermogravimetry analysis (TGA) results revealed that HGM/DOPO/EVA samples show higher thermal stability at high temperatures than EVA samples. Furthermore, the addition of HGM improved Young’s modulus compared to EVA. These results suggested the synergetic effect of DOPO and HGM additions, the high efficiency of the proposed strategy and the wide application prospect of the produced EVA flame retardant composite materials.

Reprocessable, malleable and intrinsically fire-safe epoxy resin with catalyst-free mixed carboxylate/phosphonate transesterification

Fire hazard and waste crisis are two challenges for thermosets, particularly for epoxy resins (EPs) possessing the largest market share therein; yet it is beset with difficulties to solve the challenges simultaneously. Herein, a commercialized phosphorus-containing diol named diethyl bis(2-hydroxyethyl)aminomethylphosphonate (DAP) with “trinity” structures containing phosphonate ester, primary hydroxyls and tertiary amine was applied in an epoxy-anhydride curing system to achieve the catalyst-free mixed transesterification within the adaptable carboxylate/phosphonate networks. The phosphonate structure in DAP was covalently bonded into the epoxy vitrimers (EVs), endowing the EVs with intrinsic fire safety. In detail, the peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP) and maximum smoke density (Ds max) values were considerably reduced by 62.0%, 73.6%, 78.9% and 70.8%, respectively. Meanwhile, owing to the self-catalytic tertiary amine and highly reactive primary hydroxyls from DAP, the mixed transesterification within the adaptable carboxylate/phosphonate networks was accelerated, endowing facile reprocessibility and malleability of the vitrimers, which were further degraded into low-mass molecules by simple alcoholysis. Killing two birds with one stone, this work provided a promising and feasible way to make sustainable and fire-safe thermosetting polymers with comprehensive properties.

Intumescent closed-cell porous molecular engineering towards high flame retardancy and ultra-low smoke release epoxy resin

Wide applications of high-flammable epoxy resin (EP) bring potential fire risks with huge heat and smoke hazards. Although effective strategies for flame retardancy and heat suppression have been developed, there are still few measures for reducing smoke release synchronously. Herein, 2-aminobenzimidazole modified ammonium polyphosphate intumescent flame-retardant co-curing agent (ABMZ-APP), possessing excellent char-forming performance, is designed and endows EP/ABMZ-APP thermosets with excellent flame retardancy, heat suppressing, and smoke suppressing performance. It is worth mentioning that the total smoke production (TSP), and maximum smoke density (DSmax) of EP with 20 wt% ABMZ-APP decrease by 73.2%, and 67.6%, respectively. Deep investigation illustrates EP/ABMZ-APP suppresses the smoke by obstructing soot-precursor transfer through the special porous char structure, rather than altering the chemical changes in nucleation and growth processes of mature soot. Meanwhile, the closed-cell porous char layers, acting as physical barriers, obstruct the heat/fuels transfer simultaneously which is beneficial for suppressing sustained burning.

The impact of halogen free phosphorus, inorganic and nitrogen flame retardants on the toxicity and density of smoke from 10 common polymers

AbstractThe toxicity and density of smoke from 10 commonly used commercial polymer types was studied using the European railway standard EN 45545‐2. This test method was chosen because it reflects the current state‐of‐the‐art in assessing the hazards of smoke in bench‐scale test scenarios (not because of a specific link to railway applications). The study involves 72 commercially relevant formulations provided by 12 industrial companies. Polymers studied include PE, PP, PC, PA6, PA66, u‐PVC, p‐PVC, PU, PIR, and epoxy resins. Reference samples as well as samples containing halogenated and Phosphorus, Inorganic or Nitrogen based Flame Retardants (PIN FRs) were tested according to the French tubular furnace method (NF X 70‐100) to evaluate their smoke toxicity at 600°C and according to ISO 5659‐2 at 50 kW m−2 with Annex C of EN 45545‐2 to evaluate their smoke density as well as toxicity at 4 and 8 min. This study highlights that the measured toxicity and calculated Conventional Indexes of Toxicity (CITNLP, CIT4 min, CIT8 min), as well as maximum smoke density (DsMAX) show generally no significant increase in the presence of PIN FRs in comparison to the neat polymers. The use of intumescent FRs or hydroxide based FRs generally allows considerable smoke reduction with little impact on smoke toxicity. Bromine based‐FRs were found to be detrimental to both hazards in most matrices studied here.

Single-component flame-retardant and smoke-suppressive epoxy resins enabled by an aluminum/phosphorus/imidazole-containing complex

To simplify the manufacture and address the intrinsic flammability of epoxy resin (EP) products, the single-component, fire-safe EP systems are increasingly in demand. However, current design strategy is difficult to achieve the simultaneous improvement in storage stability, flame retardancy and smoke suppression. Herein, a phosphorus/imidazole-containing, aluminum-based complex (ADIM) was synthesized, and applied as a latent curing agent for EP. The shelf life of EP/ADIM system reached 30 days, and its gel time at 150 °C was only 42 min, indicative of great thermal latency and fast curing rate. EP/ADIM thermoset showed superior flame retardancy, as confirmed by a limiting oxygen index (LOI) of 35.0% and a UL-94 V-0 classification. In addition, the total smoke production and maximum smoke density of EP/ADIM thermoset were 38.7% and 22.3% lower than those of EP thermoset cured by imidazole (EP/IM), demonstrating obviously-enhanced smoke suppression. ADIM inhibited the heat release and smoke generation of the EP matrix via radical capturing and catalytic charring. Moreover, EP/ADIM thermoset exhibited comparable thermal resistance and mechanical properties to EP/IM thermoset. Hence, this work offers an integrated design strategy for creating high-performance, fire-safe, single-component EP with well-preserved mechanical and thermal properties.

High-performance, intrinsically fire-safe, single-component epoxy resins and carbon fiber reinforced epoxy composites based on two phosphorus-derived imidazoliums

Carbon fiber reinforced polymer (CFRP) composite is a kind of lightweight material with excellent comprehensive properties, but low production efficiency and inherent flammability have become two crucial limitations for its further application. Herein, two phosphorus-derived imidazoliums (CEPM-1 and CEPM-2) were synthesized by aqueous self-assembly, and applied to flame-retardant, one-component epoxy resins (EPs). Moreover, the well-designed EPs (EP/CEPM-1–25 and EP/CEPM-2–20) were used as resin matrixes for CFRP. Both EPs featured superior latency and modest-temperature fast curing, especially EP/CEPM-1-25, which had a long shelf life of 30 days and can gel within 20 min at 150 °C. The limiting oxygen index (LOI) and UL-94 classification of EP/CEPM-1-25 were 33.0% and V-0, indicative of superior flame retardancy. The total smoke production and maximum smoke density of EP/CEPM-1-25 displayed 37.7 and 72.1% reductions relative to those of the control EP sample cured by imidazole, demonstrating improved smoke suppression. EP/CEPM-2-20 also displayed satisfactory fire safety, but slightly inferior to EP/CEPM-1-25. As expected, the CFRP composites based on EP/CEPM-1-25 and EP/CEPM-2-20 showed high LOIs (42.5 and 39.0%) and UL-94 V-0 classification due to the inhibition of P-containing groups in CEPM-1 and CEPM-2 on the wick effect. Therefore, this work proposes a facile and ‘green’ methodology to create high-performance, intrinsically fire-safe single-component EPs and CFRP composites.

Design of novel double-layer wrapped ammonium polyphosphate and its application in aging-resistant and flame retardant crosslinked polyethylene composites

In this study, double-layer wrapped ammonium polyphosphate (APP) is designed to enhance the mechanical properties, resistance and flame retardancy of crosslinked polyethylene (XLPE) composites. APP was wrapped with silica and then grafted with hindered phenol antioxidant 3-(3,5-di-tert-butyl-4 hydroxyphenyl) (AO) to prepare double-layer wrapped flame retardants (MCAPP). Due to the excellent compatibility between the MCAPP and XLPE matrix, the tensile strength and elongation at break of XLPE/MCAPP/CFA (XLPE-4) were improved. Moreover, the retention rate of elongation at break for the XLPE-4 composite reached 61.1%, significantly higher than that of XLPE-1 (2.6%) at 135 °C after aging for 14 d. This demonstrates that MCAPP could improve the aging resistance of XLPE cable composites. Compared with XLPE-1, the maximum smoke density and the peak heat release rate were reduced by 54.9% and 89.7%, respectively. Thus, the double-layer wrapping antioxidant strategy provides an excellent approach to obtain high-performance XLPE composites.

Phytic Acid-Iron/Laponite Coatings for Enhanced Flame Retardancy, Antidripping and Mechanical Properties of Flexible Polyurethane Foam.

The use of flexible polyurethane foam (FPUF) is severely limited due to its flammability and dripping, which can easily cause major fire hazards. Therefore, choosing an appropriate flame retardant to solve this problem is an urgent need. A coating was prepared on the FPUF surface by dipping with phytic acid (PA), Fe2(SO4)3·xH2O, and laponite (LAP). The influence of PA-Fe/LAP coating on FPUF flame-retardant performance was explored by thermal stability, flame retardancy, combustion behavior, and smoke density analysis. FPUF/PA-Fe/LAP has a good performance in the small fire test, which can pass the UL-94 V-0 rating and the limiting oxygen index reaches 24.5%. Meanwhile, the peak heat release rate values and maximum smoke density of FPUF/PA-Fe/LAP are reduced by 38.7% and 38.5% compared with those of neat FPUF. After applying PA-Fe/LAP coating, the value of fire growth rate index decreases from 10.5 kW/(m2·s) to 5.1 kW/(m2·s), dramatically reducing the fire risk. Encouragingly, the effect of PA-Fe/LAP coating on cyclic compression and permanent deformation is small, which is close to that of neat FPUF. This work provides an effective strategy for making a flame-retardant FPUF with antidripping and keeping mechanical properties.

NiTi-layered double hydroxide nanosheets toward high-efficiency flame retardancy and smoke suppression for silicone foam

There is a need for further enhancing fire safety of silicone foam (SiF) due to its popularization and application in aircraft and the latest generation of high-speed train. We prepared a novel NiTi-layered double hydroxide nanosheets (NiTi-LDH) by a co-precipitation method, which was used as highly effective flame-retardant and smoke-suppressor for SiF. FTIR and X-ray photoelectron spectrometerwere conducted to analyze the chemical structure of NiTi-LDH. The microstructure and crystal phase of NiTi-LDH were determined by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy. The results of atomic force microscope and Brunauer-Emmett-Teller analyses demonstrated that NiTi-LDH possessed an ultra-thin structure with an average thickness of 1.93 ± 0.02 nm and large specific surface areas (194.4 m2 g−1). After being evaluated by vertical flame testing (UL-94), limiting oxygen index (LOI), and cone calorimeter test, only 1.0 phr NiTi-LDH made SiF pass UL-94 V-0 rating with an increased LOI (28.7–30.3%), and greatly inhibited smoke release compared to untreated silicone foam. Meanwhile, both the maximum smoke density and smoke density rank of SiF/NiTi-LDH-1.0 are lower than those of SiF. To further understand the flame retardant action of NiTi-LDH, we used thermogravimetric analysis (TGA), XRD and FTIR to investigate its thermal decomposition behavior, the evolutions of chemical/crastal structures during heating. X-ray energy dispersive spectroscopy coupled with SEM (SEM-EDS) and TGA-FTIR were adopted to analyze the char residue and gaseous products. NiTi-LDH exhibited possible catalytic actions for high efficiency smoke suppression and flame retardancy based on char-forming and flammable volatiles inhibition in both the condensed and gaseous phase.