Smoke Suppression Performance Research Articles

Improvement of the flame retardance of epoxy resin composites reinforced with cyclodextrin phosphate melamine salt

AbstractEpoxy resin is widely applied in civil aircraft, automobile and electronics products because of its good processing, adhesion, and mechanical properties, but its application is limited due to its easy combustion. Therefore, it is worthwhile to carry out flame‐retardant treatment for epoxy resin. In this study, a new bio‐based three‐source integrated intumescent flame‐retardant cyclodextrin phosphate melamine salt (CDPM) was synthesized from β‐cyclodextrin, phosphoric acid, and melamine, and it was employed as an additive flame retardant to fabricate CDPM/epoxy resin (CDPM/EP) composites. Thermogravimetric analysis results manifested that CDPM slightly improved the thermal stability of CDPM/EP composites. The CDPM/EP composite containing 10 wt.% CDPM acquired a limiting oxygen index of 32.9% and passed UL94 V‐0 rating. Moreover, the peak heat release rate, total heat release, and total smoke production, were respectively decreased by 46.4%, 55.5%, and 61.8% in contrast with neat epoxy resin. These results demonstrated that CDPM/EP could exert excellent flame retardance and smoke suppression performance. Scanning electron microscope and Raman results confirmed that CDPM facilitated the formation of residual char. Moreover, thermogravimetric/infrared results showed that CDPM/EP produced plenty of phosphorus‐containing free radicals and nonflammable NH3 during pyrolysis process, which played a good flame retardance effect in gas phase. This study provides a new approach for the design and development of low‐cost intumescent bio‐based flame retardant for epoxy resin.Highlights Novel three‐source intumescent bio‐based flame‐retardant CDPM was successfully synthesized. CDPM was incorporated into epoxy resin as an additive flame retardant. Only 10 wt.% CDPM provided 55.5% and 61.8% reductions of total heat release and total smoke production, respectively. CDPM/EP composites exhibited an excellent flame retardancy and smoke suppression properties. The outstanding promoting carbonization effect of CDPM in condensed phase contributes to reduce the release of heat and smoke.

Core-shell flame retardants based on Chitosan@MMT coated ammonia polyphosphate for enhancing flame retardancy of polyurethane

In this manuscript, the core-shell flame retardants based on chitosan@MMT coated ammonia polyphosphate (APP@CS@MMT) was prepared and then incorporated into the TPU matrix. Through analyzing the effects of the flame retardant on the property reinforcements, it’s found that TPU/APP@CS@MMT composites have the excellent flame retardant and smoke suppression performance. The pHRR, THR, pSPR and TSP of TPU/APP@CS@MMT composites were remarkably decreased by 62.58%, 71.56%, 90.43%, 83.22%, and 93.60%, respectively. Furthermore, the mass of residual chars increased significantly from 0.85% for pure TPU to 21.95% for TPU/APP@CS@MMT composites. The TPU/APP@CS@MMT composites can improve both the flame-retardant and smoke suppression performances of TPU. Through the thermogravimetric test, cone calorimetry test, and char structure analysis, the flame retardant mechanism of the TPU/ APP@CS@MMT composites was also investigated. The APP@CS@MMT mainly plays its flame retardant role in the condensed phase. This work also provides a green and facile methodology for creating flame retardant TPU and helps broaden the TPU’s practical application in industry.

Biomass intumescent flame retardant polyacrylonitrile composite: flame retardancy, smoke suppression and recycling

A fully biomass intumescent flame retardant (IFR) system was fabricated by combining the reaction product ([email protected]) of phytic acid (PA) and hydrolyzed silk (HS) with potato starch (PS), which was then blended with polyacrylonitrile (PAN) to obtain flame retardant PAN (FR-PAN). The tensile strength and elongation at break for PAN-10%[email protected]/5%PS sample increased by 18.8% and 86.3%. The peak heat release rate (PHRR) and peak smoke production rate (PSPR) decreased by 54.8% and 79.3% respectively, exhibiting excellent flame retardant and smoke suppression performance. Furthermore, the PAN-10%[email protected]/5%PS sample was carbonized to prepare FR-PAN Char (FRPC), which was then used for cellulose and polyvinyl alcohol (PVA) modification. The maximum thermal decomposition rate and PHRR of modified cellulose and PVA were significantly reduced, showing the improved fire safety. This work not only prepared an eco-friendly fully biomass flame retardant PAN composite, but also realized the successful recycling of waste flame retardant PAN materials.

Research on fire retardant lignin phenolic carbon foam with preferable smoke suppression performance

In this work, a lignin phenolic carbon foam (LCF) with preferable smoke suppression performance was fabricated by substitute 10 wt.% and 30 wt.% phenol with modified lignin in the traditional process. The result showed that the LCF600s (LCFs carbonized at 600℃) with different lignin percentages showed better smoke suppression performance than the traditional phenolic carbon foam (CF600). The peak smoke production rate (pSPR) and total smoke release (TSR) of LCF600s decreased by 6.90%∼48.28% and 80.91%∼96.28%, and the peak CO production rate and CO yield decreased by 41.17%∼70.59% and 53.80%∼77.79%, respectively. Besides, LCF1-10-600 and LCF2-30-600 displayed the best smoke suppression performance (0020, 0.0015 m2/s of pSPR and 0.61, 2.76 m2/m2 of TSR, respectively). Since the introduced modified lignin significantly increased the amount of benzene rings in the forms, the degree of graphitization of the resulted carbon foams greatly improved, leading to better smoke suppression performance. Furthermore, the added lignin facilitated the preservation of the carbon layer, resulting in reducing smoke production consequently.

Recycling construction wastes to fabricate particle boards with admirable flame retardancy, smoke suppression and mechanical performance

Construction wastes (CWs) were utilized in this work as the feedstock for manufacturing wasted-based particle boards (WPBs). Results revealed that phytic acid (PA), as a natural and sustainable fire retardant, imparts the WPBs excellent flame retardancy and smoke suppression. The hydrogen bonds network formed among PA, waste particles, and adhesive improves the stress transferring of WPBs when subjected to load, thus elevating the modulus of elasticity and inner bonding strength of PA-treated WPBs. We believe that the as-proposed recycling methods promote the value-added utilization of CWs, and it is also beneficial for realizing the recycling of timber architectures.

In-situ synthesis of copper phytate-hierarchically porous MOF-199 hybrid in wood towards multifunctional flame-retardant wood composite

The modern society pays growing attention on global environmental issues, public safety, and individual health, which highlights the necessity of exploring sustainable, energy-saving, flame-retardant, and anti-mildew materials for building applications. Herein, by in-situ preparing copper phytate-hierarchically porous MOF-199 hybrid (PCuM) in natural wood (W) via simple phytate induced defect engineering strategy, we reported a multifunctional low fire-hazard wood composite (PCuM-W). The phytate anion not only acted as a modulator to generate hierarchical porosity in MOF-199, but also offered high flame retardancy due to its six phosphorus groups. The copper phytate anchored on the cell wall exhibited charring and graphitizing effects and enhanced the flame retardancy and smoke suppression performance of wood. By pyrolysis, a hierarchically porous MOF-199-derived carbon formed and offered a considerably enhanced catalytic activity towards the conversion of CO. With a weight percent gain of only 13.5%, the fire growth index, total smoke production, and maximum CO production rate of PCuM-W were 74.2%, 85.4%, and 33.3% lower than that of W, respectively, showing outstanding fire-hazard-reducing efficiency that surpassed most of its counterparts. Furthermore, due to the hierarchical porosity and antimicrobial property of PCuM, PCuM-W showed excellent moisture-buffering ability and mildew resistance. This work brings guidelines for fabricating hierarchically porous MOFs to realize multifunctional materials via phytate induced defect engineering.

Construction of layered double hydroxide composites derived from tungsten tailing particles for simultaneously enhancing fire protection and anti-ageing properties of intumescent fire-resistant coatings applied in wood surface

Tungsten tailing is a great deal of solid waste produced in the production process of tungsten metal, for which there is no simple and effective treatment method in the world. The success synthesis of layered double hydroxide composites (TTF-LDH) by co-precipitation method from tungsten tailing is a feasible way to solve this problem. The structure and properties of TTF-LDH were confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The obtained TTF-LDH was in combination with intumescent flame retardants (IFR) to achieve a series of intumescent fire resistance coatings. The effects of TTF-LDH on the fire protection, smoke suppression and anti-ageing performances of coatings were evaluated by fire resistance test, smoke density test, cone calorimeter test and accelerated ageing test, while the flame-retardant mechanism of TTF-LDH in coatings was revealed. The results illustrate that an appropriate amount of TTF-LDH can remarkably enhance smoke suppression and fire-resistant abilities of coatings, among which the coating containing 3 wt % TTF-LDH (IFRC-LDH3) exhibits the optimal synergistic effect, revealing a smoke density rating value of 17.3%, a total heat release of 7.0 MJ/m2 and an equilibrium backside temperature of 146.2 °C at 900 s. Meanwhile, the addition of TTF-LDH can strengthen the char formation and thermal stability abilities of the coatings, and the residual weight of IFRC-LDH3 rises to 35.7% at 800 °C, as supported by thermogravimetric (TG) analysis. The results of accelerated ageing test demonstrate that the presence of TTF-LDH can strengthen structural stability of coating, decrease migration and decomposition of IFR, thus giving the coating better integrity and durability of fire-resistant and smoke suppression properties.

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.

Preparation of Organic-Inorganic Phosphorus-Nitrogen-Based Flame Retardants and Their Application to Plywood.

The combustibility of wood can be improved by physical and chemical means, thus expanding the use of wood products. In this study, two novel phosphorus-nitrogen flame retardants (UCPR and MCPR) were developed, and the intercalated modified layered double hydroxides (LDH) thereof were designated as UCPR-LDH and MCPR-LDH. By impregnating poplar veneer with UCPR-LDH and MCPR-LDH solutions, the study investigated the effects of different concentrations (1%, 5%, 10%), processes (vacuum-pressure impregnation, room temperature impregnation, normal-pressure impregnation), and impregnation times (2 h, 3 h, 24 h, 48 h) on the weight-gain rate of veneer. The optimal process was then selected for preparing formaldehyde-free three-layer plywood. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) were used to characterize the UCPR and MCPR. Meanwhile, gel-permeation chromatography (GPC) demonstrated that the molecular weight of the synthesized flame retardants increased as their molecular distribution became more uniform. The impregnation process was performed at normal temperature and pressure for 48 h at a 5% flame retardant concentration. Results from cone calorimetry indicate that the UCPR-LDH plywood exhibits a peak heat release rate that is 30.43% lower than that of the control group, demonstrating superior thermal barrier performance. The smoke emission of the MCPR-LDH plywood was reduced by 33.62% compared to the control group, indicating superior smoke suppression performance. This method presents a viable approach for synthesizing organic-inorganic flame retardants.

A highly thermostable flame retardant for poly(ethylene terephthalate) and its fabric with satisfactory comprehensive flame retardancy

The charring enhancement of polymers at high temperatures is essential for improving their anti-dripping, flame inhibition and smoke suppression performance. In this work, a highly thermostable and charring phosphorus-nitrogen (P/N)-based flame retardant (HMCP), which can boost the char-forming of poly(ethylene terephthalate) (PET) was synthesized. Amazingly, melt-dripping of PET was completely suppressed as 4 wt% of HMCP was added. For PET composite with 8 wt% of HMCP (PET/HMCP8), its limiting oxygen index increased to 33.6% and the flame self-extinguished within 5 s. Besides, the after-flame time and total smoke production of PET/HMCP8 were reduced by 96.1% and 39.5% respectively compared with pure PET. The enhanced fire safety of PET/HMCP composites was attributed to the barrier effect and the dilution effect produced by the synergism of P/N-based heterocycle and benzimidazole groups. Additionally, PET fabric woven with the filaments prepared by the melt spinning of PET/HBCP4 presented pleasing fire safety and mechanical properties.

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.

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.

Synthesis of solid reactive organophosphorus‐nitrogen flame retardant and its application in epoxy resin

AbstractA solid reactive organophosphorus‐nitrogen flame retardant 4N‐BDP was devised and synthesized in order to address the flaws of the widely used organophosphorus flame retardants BDP as well as the issue of flame retardant modification of epoxy resin (EP). A series of flame‐retardant EP composites were prepared by adding 4N‐BDP and BDP to EP in a specific proportion. The flame‐retardant properties of the two were compared, and the flame‐retardant mechanism of 4N‐BDP was deeply analyzed. The results of the UL‐94 test revealed that sample 4N‐BDP‐6 obtained the greatest V‐0 level, while BDP‐6 had no level, when the addition ratio of flame retardant was 8.03%. In the cone calorimeter test, the peak smoke production rate (pSPR) and total smoke production (TSP) of BDP‐6 were not significantly different from those of pure EP. In contrast, TSP and pSPR of 4N‐BDP‐6 decreased by 39.50% and 50.00% respectively compared with EP. Compared with BDP, 4N‐BDP shows better flame retardancy and smoke suppression performance, which can significantly improve the fire resistance of EP. The flame‐retardant mechanism of 4N‐BDP was resolved by scanning electron microscopy, XPS, and thermogravimetric analysis/infrared spectrometry. 4N‐BDP can increase the residual carbon rate of the composites, improve the residual carbon strength, play an excellent condensed phase flame retardant effect, and avoid further decomposition of the materials. In the gas phase, the decomposition of 4N‐BDP produces PO·, PO2· and NH3, which play a good quenching effect and dilution effect. The escape of NH3 will leave bubbles in the residual carbon, making the residual carbon more fluffy, further improving the ability of heat insulation and oxygen insulation, and enhancing the flame retardant effect of the condensed phase. In general, the flame‐retardant mechanism of 4N‐BDP is a synergistic combination of condensed phase and gas phase flame retardant mechanism. This work provides a new approach to improve the defects of organophosphorus flame retardant BDP commonly used in the market and enhance the fire resistance of EP.

Application of the PAPP/MCA/APP intumescent flame retardant system in polypropylene

AbstractAmmonium polyphosphate (APP), piperazine pyrophosphate (PAPP), and melamine cyanurate (MCA) were used as raw materials to develop an intumescent flame retardant system (IFRS) for polypropylene (PP). The synergistic flame retardancy among APP, PAPP, and MCA was explored. The effect of the proportion of APP, PAPP, and MCA on the IFRS flame‐retardant performance was studied. For the range of samples tested, the IFRS with the proportion of PAPP, MCA, and APP at 4:1:7.5 showed the best flame retardancy. When the addition of PAPP/MCA/APP IFRS in PP was 20%, the prepared flame‐retardant PP composite (PP‐PMA‐3) passed UL‐94 V‐0 rating. Moreover, the PP‐PMA‐3 total heat release (THR) decreased by 46.4% compared with PP‐0. Meanwhile, PAPP/MCA/APP IFRS showed good smoke suppression performance because the total smoke production (TSP) of PP‐PMA‐3 decreased by 65.0% compared with PP‐0. In addition, the high flame retardancy and the flame‐retardant mechanism of the prepared IFRS was explained.

Synergistic effect of zinc borate and microencapsulated black phosphorus nanosheets for improved flame retardancy and smoke-suppression performance of epoxy resin

To improve the air stability and smoke-suppression ability of black phosphorus nanosheets (BPNs), a simple strategy was proposed. Through microencapsulation of BPNs with pentaerythritol triacrylate (PETA), BPNs@PETA was synthesized. The ZB-BPNs@PETA was obtained through combining zinc borate (ZB) with BPNs@PETA at the ratio of 1:1. The ambient and thermal stability of BPNs was improved after modification due to the protection of PETA shell. The maximum rate of thermal degradation of BPNs for BPNs@PETA and ZB-BPNs@PETA was reduced by 36.87% and 72.38%, respectively, compared with that of BPNs. The results confirmed that PETA and ZB can delay the pyrolysis of BPNs greatly. With the addition of 2.0wt% ZB-BPNs@PETA, the fire safety and thermal stability of EP nanocomposite was improved. EP/ZB-BPNs@PETA 2.0 can pass the UL-94 V-0 rating, and the limited oxygen index value was increased to 32.2% from 25.0%. The values of peak of heat release, total heal release, smoke production rate and total smoke production were reduced by 43.53%, 22.05%, 30.17% and 14.14%, respectively. Additionally, the results of TG-IR showed that ZB-BPNs@PETA can reduce the peak value of absorption intensity of CO by 34.11%, compared with that of EP. From the results of XRD, the presence of Zn3(PO4)2, BPO4 and B2O3 verified the synergistic effect of ZB and BPNs@PETA during combustion. In short, the catalytic dehydration carbonization effect of BPNs improved by PETA and ZB, can largely account for the decrease in fire hazard of EP composites. This work offered a new way to simultaneously improve the smoke-suppression ability and flame-retardant efficiency of BPNs.

Remarkable effects of silicone rubber on flame retardant property and mechanical properties of crosslinked high‐density polyethylene/bio‐based magnesium phosphate flame retardant (MHPA) composite

AbstractIn this paper, a new bio‐based flame retardant MHPA was prepared by the reaction of magnesium hydroxide (MH) and phytic acid (PA). Then the crosslinked high‐density polyethylene (HDPE) flame‐retardant composite was prepared by adding it and silicone rubber (SR) into HDPE and using electron beam irradiation. The test results of limiting oxygen index (LOI) and cone calorimeter test (CCT) show that the combination of MHPA and SR can increase the flame retardancy and smoke suppression performance of HDPE. The LOI of HDPE composite with 10 parts of SR is 28.3%, and its pHRR, THR and TSP values are reduced to 454.1 kW/m2, 99.7 MJ/m2 and 8.3 m2, respectively, which is because MHPA and SR jointly promote the formation of continuous and high‐density carbon slag in the combustion process of HDPE and inhibit the penetration of flame. In addition, the HDPE composite with 10 parts of SR has significant tensile strength, elongation breaking strength and tear strength, because SR can produce continuous stable structure with HDPE after irradiation and crosslinking. Therefore, this study verified that MHPA and SR together can effectively improve the flame retardancy, smoke suppression and mechanical properties of HDPE composite.

Study on Flame Retardancy Behavior of Epoxy Resin with Phosphaphenanthrene Triazine Compound and Organic Zinc Complexes Based on Phosphonitrile

A novel flame retardant phosphorus-containing organozinc complex (Zn-PDH) was prepared using zinc and iron as the metal center and 4-aminopyridine, with low steric hindrance, as the organic ligand, then using phosphazene to modify the organometallic complex (Zn-4APD). The flame retardant properties and mechanism of Zn-PDH/Tris-(3-DOPO-1-propyl)-triazinetrione (TAD) in epoxy resin (EP) were investigated. Flame inhibition behavior was studied by the vertical combustion test (UL94), while limiting oxygen index (LOI) measurement and flame retardant properties were studied by the cone calorimeter test (CONE). The flame retardant modes of action were explored by using the thermogravimetry-Fourier transform infrared (TG-FTIR) test, X-ray photoelectron spectrometer (XPS), and Raman spectroscopy (LRS). When TAD and Zn-PDH were added to the epoxy resin in the ratio of 3:1, the system achieved a balance between the gas-phase and condense-phase actions of the flame retardant effects, and the 3%TAD/1%Zn-PDH/EP composite system achieved not only good flame inhibition but also obtained good smoke and heat suppression performance, showing a comprehensive flame retardant performance. The gas phase and Zn-PDH mostly promoted charring with a barrier and protective effect in the condensed phase. As for the mechanism, TAD released the phosphorus-containing radicals and phenoxy radicals during decomposition and mainly exerted a gas-phase quenching effect. While in the condense phase, Zn-PDH promoted the decomposition of the polymer matrix to produce more aromatic structures and rapidly formed a complete and dense carbon layer rich in P-O-C crosslinked structures at high temperatures. Meanwhile, more N entered the gas phase in the form of inert gas, which diluted the concentration of the combustible fuel and helped to inhibit the combustion reaction.

Bismuth stannate nanoparticles for enhancing fire safety of flexible polyvinyl chloride: Preparation, evaluation, and mechanism

To replace traditional toxic Sb2O3 flame retardants, Bi2Sn2O7 (BSO) nanoparticles were prepared by a co-precipitation method and used as flame retardants of flexible polyvinyl chloride (PVC) for the first time. Structural characterization revealed that as-prepared BSO nanoparticles had a cubic phase with an average diameter of 20 nm. Under 3 wt% loading, the PVC/BSO composite gained a limiting oxygen index of 29%, very close to 29.5% of PVC/Sb2O3. In particular, the PVC/BSO composites passed the UL-94V-0 rating, while PVC/Sb2O3 failed. The PVC/BSO composite also showed better heat and smoke suppression performance than Sb2O3, with a 27.4% decrease in peak heat release rate and a 39.9% decrease in total smoke production, compared with the PVC matrix. The excellent performance is attributed to following two reasons: In the gas phase, similar to Sb, Bi can form BiCl3, which dilutes the combustion gas and captures hydroxyl radicals; In the condensed phase, Sn in BSO helps form more protective char residue with the least pores and the highest degree graphitization. In addition, the tensile strength and elongation at break of PVC/BSO were also slightly superior to those of PVC/Sb2O3. In conclusion, BSO nanoparticles will be a promising substitute for toxic Sb2O3 flame retardants.

Preparation and Properties of Smoke Suppressive Silicone Oil Modified by Dicyandiamide

In order to improve the smoke suppression of silicone oil, relatively high nitrogen content silicone oil was synthesized by the reaction of dicyandiamide (DCD) and epoxy-terminated silicone oil (ETSO) and named DCDSO. The molecular structure of DCDSO was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). The flame ignition and cone calorimetry test (CCT) were used to investigate the smoke suppression effect of DCDSO. The results showed that the introduction of DCD significantly improved the smoke suppression performance of DCDSO. When the molar ratio of the epoxy group in ETSO and the primary amino group in DCD was 1:1.3, the flame height and the total smoke production were significantly reduced. Thermogravimetric analysis (TGA), thermogravimetric infrared analysis (TG-IR) and thermal field emission scanning electron microscopy (SEM) were used to explore the mechanism of smoke suppression. The mechanism of smoke suppression is that the introduction of DCD reduces the rearrangement decomposition, promotes the free radical oxidation decomposition and the formation of condensed phase, and thus reduces the generation and release of smoke.

Fabrication of flame-retardant and smoke-suppressant rigid polyurethane foam modified by hydrolyzed keratin

Abstract Rigid polyurethane foam (RPUF) has been fabricated and modified by hydrolyzed keratin to improve its flame retardancy and smoke suppression. Then, the limiting oxygen index (LOI), cone calorimeter (CONE), thermogravimetric analyzer and scanning electron microscope (SEM) were used to characterize the modified RPUFs. It was found that the LOI of the modified RPUFs increased with the presence of hydrolyzed keratin. In addition, the peak heat release rate (PHRR) and total heat release (THR) of the modified RPUF tended to decrease. The HRR of RPUF-HK5 reduced 28.8 kW/m2 compared with RPUF-0, and the THR of RPUF-HK5 was 0.74 MJ/m2 lower than that of RPUF-0. RPUF-HK5 had the most obvious smoke suppression effect. Compared with RPUF-0, the smoke density (Ds) and light transmittance (T) of RPUF-HK5 decreased by 8.88 and increased by 11.26%, respectively. The current research results showed that hydrolyzed keratin can improve the flame-retardant and smoke-suppression performances of RPUFs and that 5 wt% hydrolyzed keratin was the most suitable ratio for the modified RPUF.