Fire Growth Index Research Articles

A silicone diphenylsulfonate for improving the flame retardancy of polycarbonate

AbstractSilicone diphenylsulfonate (SDPSF) was synthesized via nucleophilic substitution reaction between dihydroxyalkyl‐terminated silicone oil and benzene sulfonyl chloride, and its chemical structure was confirmed by Fourier transform infrared (FTIR) and 1H NMR. The effect of SDPSF on the flame retardancy, thermal stability, combustion behavior, and mechanical properties of PC/SDPSF blends were investigated. The PC/2 wt% SDPSF blend achieved the UL‐94 (3 mm) V‐0 rating and limiting oxygen index value of 30.3% together with the lowest values of the total heat release (32.2 MJ/M2), peak heat release rate (239.5 kW/M2), CO production (0.48 kg/kg), and fire growth index (1.09 kW/s·m2). It demonstrated that the SDPSF improved evidently the flame retardancy and fire safety of the polycarbonate (PC) matrix. The blend also gave a slightly reduced tensile strength (60.0 MPa) and notched impact strength (57.0 kJ/m2). The TG‐FTIR spectra of the pyrolysis gases demonstrated that the SDPSF promoted the decomposition of PC matrix on advance to release much more nonflammable gases in the early combustion process, meanwhile, the analysis of the char residues confirmed that the SDPSF facilitated the formation of compact and continuous layers with higher graphitization degree to isolate the transfer of heat and combustible volatiles.

Group aggregation effect of polyphenolic phosphaphenanthrene macromolecule on enhancing fire safety and toughness of epoxy thermoset

Polyphenolic phosphaphenanthrene macromolecule (PDBA) was synthesized from 2,2’-di(phosphaphenanthrene-propyl)-bisphenol A (DDBA), via phenol-formaldehyde condensation. With molecular-scale group aggregation feature, PDBA macromolecule exhibits obviously higher efficiency than its starting monomer DDBA in improving the anti-impact, anti-ignition, and self-extinguishing performance of epoxy thermoset (EP). 3%PDBA/EP exhibited a 77.2% higher impact strength than that of neat EP, passed UL94 V-0 rating with a limited oxygen index of 32.8%, and achieved 25.3% lower peak of heat release rate, 16.0% lower fire growth index, and 18.6% higher fire performance index, compared with neat EP. PDBA macromolecule also performs better in reducing thermal-decomposition mass loss rate, improving char residue quality, inhibiting combustion intensity, and maintaining anti-heat deformation performance of epoxy thermoset, compared with equivalent-addition DDBA monomer. With aggregated phosphaphenanthrene and phenolic groups, PDBA macromolecule not only impels epoxy thermoset to undergo toughness fracture with larger quantity of impact energy consumption, but also promotes burning thermoset forming more dense and intact charring residue with better barrier effect. Polyphenolic phosphaphenanthrene macromolecule with group aggregation feature exhibits its superiority in manufacturing advanced fire safety polymer materials with superior comprehensive performance.

Photothermal and fire-safe epoxy/black phosphorene composites: Molecular structure analysis of sutured char

To overcome the high flammability of polymers and endow them with photothermal capability, we fabricate the targeted nanofiller black phosphorus (BP) based SL-EBP-CoP for epoxy. Interestingly, the good ability of photothermal for EP/SL-EBP-CoP2.0 nanocomposite changes with irradiation power can be linearly quantified (r2 > 0.94). Secondly, EP/SL-EBP-CoP2.0 separately reduces peak heat release rate (HRR), total HRR and peak carbon monoxide (CO) production by 59.88%, 39.26% and 36.41% compared with EP, along with the lowest fire growth index. The significantly reduced hazard of heat and CO is attributed to the combined effects of 2D BP, catalysis of CoP and the structure of sutured char. Finally, the pyrolysis of BP-based flame retardants produces P4, P3 and P2 with an abundance of 77.10%, 6.75% and 14.70%. Moreover, flame retardant composites are highly dependent on the final char. This work demonstrates that phosphorus and P-O-P (POx) are nodes and bonding units in the char, POx bonds to the hydrocarbon fragments through P-O-C bonds. Particularly, pyrolysis molecules of suture and rupture of char (CnH2n+2PO4, m/z = 168, 139 and 124) are first discovered. This work booms the path and lays the foundations for the photothermal and fire safety of BP nanocomposites.

A strategy to improve the compatibility of carboxyl methyl cellulose with silica fume‐based geopolymer inorganic siliceous coatings for flame‐retarding plywood

AbstractTo seek an effective strategy for improving the compatibility of carboxyl methyl cellulose (CMC) with silica fume‐based geopolymer composite flame‐retarding coatings, a novel silica aerogel (SA) doped inorganic siliceous hybrid coating is fabricated by sol–gel. Results show that an appropriate dosage (0.5 wt%) of SA ameliorates their compatibility thus imparting an enhanced flame resistance, evidenced by the lowest value of fire growth index (0.22 kW·m−2·s−1) decreased by 55% and the average effective heat of combustion (4.16 kW·kg−1) decreased by 31%, the raised flame retardancy index of 5.54 from 1 compared with the control. Because the SA improves the compatibility between the CMC and siliceous colloidal sol, due to its high reactivity, electrostatic repulsion involved in SiO(OH)3−, and high porosity, leading to an enhanced crosslinking during film‐forming of the hybrid coatings. Meanwhile, the reduction between CMC and silica occurs with a swelling fire shield, evidenced by the generated silicon involved in the as‐formed amorphous siliceous residues. Therefore, it proposed a new strategy for optimizing the compatibility of organic–inorganic hybrid fireproof coatings, revealing an efficient design of CMC/inorganic siliceous flame retardants, high‐value recycling technology of solid waste, low‐carbon, and sustainable materials.

Preparation of a cobalt metal-organic framework (Co-MOF) and its application as a polypropylene flame retardant by compounding with melamine polyphosphate

A cobalt metal-organic framework (Co-MOF) was successfully prepared, and its combination with melamine polyphosphate (MPP) was studied to enhance the fire retardant properties of polypropylene (PP) composites. The morphology, composition, and structure of PP/MPP/Co-MOF composites were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The maximum limiting oxygen index of the PP/MPP/Co-MOF composite was 26.8%, which is 49% higher than that of pure PP and its combustion grade reached the V-0 level. When 2 wt% Co-MOF was added, the carbon residue of the composite reached 19.6 wt%, peak heat release rate was significantly reduced, smoke emission was suppressed, fire growth index was significantly reduced, and the fire risk of the composite was effectively reduced. Analysis of the carbon residue showed that aggregated carbon spheres were present on the carbon residue surface of the composite material supplemented with Co-MOF. The generation of carbon spheres effectively prevented the heat exchange and release of combustible gas during the combustion of the composite material, significantly improving the flame retardancy and stability of the material. As a new material, MOF has great innovation and necessity in researching polymer flame retardant. Moreover, the latest composite materials synthesized in this paper contribute to environmental safety to a great extent.

Evaluate the effect of graphene and milled glass fibre on the thermal, flame and dielectric properties of silicone elastomer filled with aluminium hydroxide

In this work, the thermal stability, thermal conductivity, dielectric frequency response, smoke factor (SF), fire performance index (FPI), and fire growth index (FGI) of silicone elastomer composites were studied and compared. TGA/DTG results indicated that the addition of graphene nanoplatelets (GNP)/milled E-glass fibres (MGF) improved the thermal stability of silicone composites by increasing the Tmax2, T20% and T30%, whereas thermal conductivity was improved by 93%–115% compared to RTV1 and 12%–24% compared to RTV2. Based on the GNP/MGF loadings, a low relative permittivity and low dielectric loss were observed. Furthermore, GNP/MGF filled silicone composites exhibited high FPI and low FGI, and microstructure analysis revealed a compact bottom char layer with no crevices on the surface. The most promising silicone composites were RTV4 and RTV5, which had higher thermal stability, improved thermal conductivity, excellent FPI and FGI values, and excellent dielectric properties, making them more suitable for electrical outdoor insulation exposed to fires.

Effect of immersion time on the combustion characteristics of oil‐impregnated transformer insulating paperboard

AbstractTransformer insulating paperboard is an insulating material commonly used in the oil‐filled equipment in substations, which is usually immersed in the transformer oil. In this study, the effects of immersion time on the combustion characteristics of oil‐impregnated transformer insulating paperboard are studied using the thermogravimetric, UL94 vertical flammability, and cone calorimeter experiments. The experimental results show that the total oil content increases with increasing immersion time and reaches the saturation state in 240 h, with a saturation content of 14.7% ± 0.5%. However, the distribution of oil content inside the paperboard is uneven. At the saturation state, the surface oil content is 35.5%, being about 3 times of the core oil content. The results of UL94 vertical flammability experiments show that the flame spread rate increases with increasing immersion time and is controlled by the total oil content. In the cone calorimeter experiments, the time to ignition is significantly reduced compared to the clean paperboard. Unlike the flame spread rate, the ignition time is controlled by the surface oil content and barely varies with immersion time. The critical heat flux of oil‐impregnated transformer insulating paperboard is found as 3.9 kW/m2, being only 1/3 of clean paperboard. With increasing immersion time, the peak heat release rate increases, while the total heat release, fire growth index, and effective heat of combustion present linear correlations with the total oil content. The CO yield increases with increasing immersion time, and the released CO mainly comes from the combustion of transformer oil.

Organic-inorganic hybrid engineering MXene derivatives for fire resistant epoxy resins with superior smoke suppression

It is a challenge to integrate organic and inorganic materials to build organic–inorganic hybrid, high-efficiency flame retardants with synergistic effects of both to diminish the fire risks of polymer composites. In this work, an organic–inorganic hybrid strategy was used to prepare leaf-like MXene-based flame retardants (MXene@Bi-MOF) by in situ growth of bimetallic metal–organic frameworks (Bi-MOF) on the surface of MXene and the hybrids were incorporated into epoxy resins to explore their flame retardancy and smoke suppression effects. Specifically, the introduction of MXene@Bi-MOF hybrids not only achieved homogeneous dispersion in EP matrix, but also improved the thermal properties of EP composites, with a 27.7% lower maximum mass loss rate (Rmax) than that of pure EP. In addition, EP composites containing 2 wt% MXene@Bi-MOF exhibited improved fire safety, reduced heat release and inhibited smoke production, as evidenced by a 28.8%, 45.3%, 36.5%, 30.7% and 55.3% drop in peak heat release rate (PHRR), peak smoke production rate (PSPR), total heat release (THR), peak CO production rate (PCO) and smoke factor (SF) value, respectively, as well as growing char yields and lower fire growth index (FGI) value, compared to those of pristine EP. The synergistic action of MXene and Bi-MOF, mainly including the blocking effect of MXene lamellar structure, catalytic carbonization effects as well as catalytic attenuation of the transition metal oxides and gas phase dilution from Bi-MOF, was primarily responsible for the improved fire safety of EP composites.

ADOPO‐anchored benzothiadiazole derivative toward efficiently P/N/S synergistic flame retarding of epoxy thermoset

AbstractFlame‐retarded epoxy thermosets are highly desirable for electronics‐related basic materials in the new‐generation information applications. Herein, a DOPO‐anchored benzothiadiazole flame retardant, namelyDOPO‐BTD, is designed and synthesized for P/N/S synergistic flame‐retarded epoxy thermosets.DOPO‐BTDpossesses good thermal stability and excellent compatibility with the epoxy matrix. As reflected by UL 94 test, theDOPO‐BTDcoated EP passes the V0 rating and achieves a higher LOI value of 34.6% at ultralow P content of 0.39 wt%. The investigation of theDOPO‐BTD‐triggered P/N/S synergistic flame‐retarded effect by thermal images further validated the flame retarded efficacy and dramatic inhibition of the flame. Meanwhile, the incorporation of 4.8 wt%DOPO‐BTDinto the epoxy matrix, the PHRR, THR, SPR, TSP, and COP are significantly decreased by 37.97%, 27.44%, 25.49%, 19.83%, and 31.70%, respectively. Additionally, the fire growth index (FGI) is sharply dropped 26.06%. Moreover, the TGIR and TGMS results convince the flame‐retarded mechanism ofDOPO‐BTDthrough the combination of the gas‐phase and condensed‐phase pathways. The P/N/S synergisticDOPO‐BTDcan serve as a promising flame retardant for efficiently fabricating the flame‐retarded epoxy thermosets, and this study sheds light on the development of multiple elements synergistic flame‐retardants for functional polymers with great application potential.

Preparation of flame-retardant HDPE composites with synergistic strategy by the combination of phosphorus-containing modifier and magnesium oxychloride cement

Magnesium oxychloride cement (MOC), as an inorganic gel material with 5Mg(OH)2·MgCl2·8H2O as its main component, has higher heat absorption and water yield during thermal decomposition than that of magnesium hydroxide (MH). It can also be used in flame-retardant polymer materials like MH. The flame retardancy of HDPE/MOC composites increases with the addition of MOC. Compared with pure HDPE, when the MOC filling amount is 60 wt%, the total heat release and total smoke production decrease by 50.6% and 50.8% respectively, and the total heat release per mass for HDPE decreases from 53 kJ/g to 32.2 kJ/g. Phosphoric acid (PA) shows a good synergistic flame-retardant effect with MOC while improving the water resistance of MOC. After adding 1 wt% PA, the peak heat release rate and peak smoke production rate of HDPE/MOC/PA (50/49/1) decrease by 30% and 25.6% respectively, and the fire growth index (FGI) decreases by 24.6%. Phosphorus-containing coupling agent (isopropyl tri(dioctylpyrophosphate) titanate) can improve the size distribution of MOC, and also has synergistic flame-retardant effect with MOC in HDPE/MOC composites.

An insight into pyrolysis and flame retardant mechanism of unsaturated polyester resin with different valance states of phosphorus structures

This work analyzes the effect of different valence states in phosphorus structures on thermal stability, pyrolysis kinetics and flame retardancy of unsaturated polyester resin (UPR). Then, the corresponding mechanisms are systematically analyzed. The poly(ethylene phenylphosphonate) (PBEG) and poly(ethylene phenoxyphosphate) (POEG) were synthesized, and the combustion behaviors of UPR, such as pyrolysis, ignition, heat suppression and charring capacity were studied. The phosphorus structures with +5 valence states in POEG was more conducive to formation of carbon layers than that of +3 valence states in PBEG. The better charring capacity made pyrolysis activation energy (Ek) of UPR/POEG different from UPR/PBEG in F-W-O and DAEM fitting methods. The Ek of UPR/POEG was larger than pure UPR at high mass conversions, but Ek of UPR/PBEG was less than pure UPR during entire pyrolysis process, due to different phosphorus-containing pyrolysis products. For PBEG, more phosphorus-containing species existed in gaseous phase to capture H· radicals; By contrast, POEG left more products in condensed phase, promoting the formation of thermally stable carbon layers. Different phosphorus-containing products also affected flame retardancy of UPR. UPR reached UL-94 V0 with only 15 wt% of PBEG, where peak heat release rate (PHRR), total heat release (THR), fire growth index (FGI) were obviously reduced. However, flame retardant efficiency of POEG were lower than PBEG. This indicates that +3 phosphorus valance of PBEG is more helpful to improve flame retardancy of UPR, and the essential reasons have been systematically analyzed. Meanwhile, the selection of high-efficiency flame retardant systems for UPR materials can be based on gaseous-phase mechanism and supplemented by condensed-phase mechanism.

Phosphorus/nitrogen compound and zinc hydroxystannate‐modified graphene oxide for efficient flame retardancy and smoke suppression of epoxy resin

AbstractDespite many important industrial applications, epoxy resin (EP) suffers from high flammability and toxicity emission. To circumvent the problem, phosphorus/nitrogen compound and zinc hydroxystannate‐modified graphene oxide is successfully fabricated. The functionalized graphene (FGO) exhibits high thermal stability and excellent dispersity in the EP matrix. The storage modulus of EP/FGO2 increases to 2713 MPa from 2176 MPa. Meanwhile, the results show a significant reduction in fire, smoke, and toxicity hazards. Compared with pure EP, incorporating only 2.0 wt% FGO2 into EP, smoke production rate, the peak heat release rate, and peak carbon monoxide production are dramatically reduced by 40.1%, 40.3%, and 37.7%, respectively. Especially, the fire growth index of EP/FGO2 is reduced by 36.0%. Moreover, the limiting oxygen index value of EP/FGO2 enhances to 28.5% and its UL‐94 achieves V‐1 rating. These superior fire safety properties are due to the catalytic, barrier effect of the FGO, the compact char blocks the diffusion of smoke and heat during combustion. This work provides an efficient strategy to prepare a promising graphene‐based flame retardant to improve the fire safety and mechanical property of EP.

Effect of expansion temperature on the properties of expanded graphite and modified linear low density polyethylene

Abstract To study the influence of expansion temperature on the properties of expanded graphite (EBG), EBG300, EBG600, and EBG900 were prepared by heating expandable graphite (EG) at 300, 600, and 900 °C, respectively. Furthermore, the influence of these EBGs on the combustion performance and physical-mechanical properties of linear low density polyethylene (LLDPE) were investigated. The expansion volumes of EBG300, EBG600, and EBG900 increase with the rise of temperature, and a four-stage ordered structure of “graphite worm” gradually forms. The thermal stability increases gradually for EBG300, EBG600, and EBG900. On the contrary, the thermal conductivity decreases in sequence. However, the incorporation of EBG900 promotes the formation of a continuous network structure and makes the modified LLDPE to present the best heat transmission. The addition of 30 wt% of these EBGs significantly improves LLDPE’s flame retardancy and high-temperature thermal stability. The total heat release, the peak value of heat release rate, and the fire growth index of 70LLDPE/30EBG300 reduce by 69, 91, and 87% respectively, while the effective fire performance index improves seven times. The addition of these additives reduces the tensile strength and elongation at break, the larger the EBG size, the more obvious the effect.

Nano-ZnO modified geopolymer composite coatings for flame-retarding plywood

Herein the nano-ZnO/melamine polyphosphate (MPP) co-doped silica fume-based geopolymer composite coatings is fabricated for flame-retarding plywood. Its flame-retarding mechanism is investigated by microstructural characterizations and pyrolysis kinetics. The results show that an appropriate dosage of nano-ZnO (0.47 wt%) enhances flame retardancy, evidenced by the fire performance index increased to 2.98 s·m2·kW−1 from 1.10, the fire growth index (FGI) decreased from 0.48 to 0.23 kW·m−2·s−1, the flame retardant index (FRI) climbs from 1 to 2.79. Because the doped ZnO initiates the formation of ceramic-like Si/C/P residues, the as-formed ZnP4O11 is determined through the reactions between MPP and nano-ZnO. The ceramic-like reactions make the pyrolysis Eα rise from 204.30 to 255.61 kJ·mol−1 at 800 ∼ 1000 °C, according to the as-identified three-stage deceleration function (F3) of pyrolysis kinetics, resulting in the resilient and interpenetrating residues with a formaldehyde adsorption rate of 56%. It seeks effective recycling of metallurgical solid waste for preparing ecological flame-retarding coatings, proposing an efficient approach for quantitatively probing the Si/C/P residues.

Pyrolysis and combustion characteristics of typical waste thermal insulation materials

Thermal insulation materials are important for building energy conservation, but their wastes have increased sharply. Furthermore, pyrolysis and combustion are increasingly utilized to dispose of solid wastes and convert them into value-added fuels. To better understand the pyrolysis and combustion characteristics of these materials, typical thermal insulation materials (expanded polystyrene (EPS) and extruded polystyrene (XPS)) were investigated by employing thermogravimetry and differential scanning calorimetry as well as cone calorimetry experiments. Pyrolysis behavior, kinetic parameters, pyrolysis index, thermodynamic parameters, endothermic properties and combustion parameters were estimated comprehensively. The results showed that EPS had better pyrolysis properties, while XPS had better combustion characteristics. Activation energies of EPS and XPS were 158.82 kJ/mol and 200.70 kJ/mol, respectively. Additionally, EPS had a higher pyrolysis stability index and comprehensive pyrolysis index, meaning a more intense reaction. Moreover, thermodynamic parameters indicated that the devolatilization products could be obtained easily from the two materials, and EPS and XPS could be converted into fuels. For the combustion, XPS had a smaller fire performance index and a larger fire growth index. These results can guide the reactor design and optimization for better converting polymer wastes into fuels and managing wastes.

Engineering two nitrogen-containing polyhedral oligomeric silsesquioxanes (N-POSSs) to enhance the fire safety of epoxy resin endowed with superior thermal stability

Despite remarkable advances in developing flame retardants and smoke suppressants for epoxy resin (EP), engineering nitrogen-containing polyhedral oligomeric silsesquioxane (N-POSS) to impart superior fire safety properties to EP has remained an intractable challenge. In this work, two nitrogen-containing polyhedral oligomeric silsesquioxanes (N-POSSs), namely, aminoethyl-aminopropyl-hepta-phenyl polyhedral oligomeric silsesquioxane (AEAP-POSS) and aminopropyl-hepta-phenyl polyhedral oligomeric silsesquioxane (AP-POSS), were synthesized through the “corner-capping” reaction. The molecular structures of N-POSSs were fully characterized by FTIR, 1H NMR, 29Si NMR and MALDI-TOF MS, and the synthesized AEAP-POSS and AP-POSS were introduced into EP to solve the shortcomings of flammability. TGA results showed that the incorporation of 4 wt% N-POSS nanoparticles distinctly improved the char residue at 800 °C, which significantly enhanced the thermal stability of the EP composites. When 4 wt% of AP-POSS was introduced into EP, reductions in the peak of heat release rate (p-HRR), fire growth index (FGI), peak of smoke production rate (p-SPR), and the peak of CO production rate (p-COP) reached to 60.6%, 70.2%, 52.3% and 60.4%, respectively. Subsequently, TG-FTIR and XPS were utilized to investigate the flame retardancy and smoke suppression mechanism. Our work presented a considerable advancement for the facile fabrication of flame retardants based on nitrogen-containing polyhedral oligomeric silsesquioxane compounds.

Novel design of MOFs-based hierarchical nanoarchitecture: Towards reducing fire hazards of epoxy resin

The inherent inflammability of epoxy resin (EP) has seriously limited its further application. The structural design of flame retardants has huge potential for boosting the fire safety properties of polymer materials. Herein, a novel MOFs-based hierarchical nanoarchitecture (ZIF-8@PA@SiO2) was constructed, composed of ZIF-8 nanoparticles, as well as in-situ grown phytic acid (PA) and silica. The results indicated that not only was ZIF-8@PA@SiO2 uniformly dispersed in the EP matrix, but it also formed a good interface bond, which was beneficial to boosting the thermal and fire safety properties of EP composites. The incorporation of ZIF-8@PA@SiO2 markedly decreased the maximum weight loss rate (MLRmax) and increased char residues. Compared with neat EP, the limiting oxygen index (LOI) value of EP/5% ZIF-8@PA@SiO2 increased from 23.4% to 28.8%. Furthermore, the peak heat release rate (PHRR), fire growth index (FGI), peak smoke production rate (PSPR), peak CO production rate (PCOPR) and smoke factor (SF) were decreased by 38.3%, 41.6%, 45.5%, 42.9% and 69.3%, respectively. The TG-FTIR results provided strong evidence for suppressed emissions of CO, aromatic, hydrocarbons and carbonyl, further corroborating the impeded heat release and the hindered fire toxicity, which were primarily ascribed to the barrier effect, free-radical scavenging and dilution effect of the multi-integrated P/N/Si-containing MOFs-based hierarchical nanoarchitecture.

Improving the flame retardancy of epoxy resin with ZIF‐67@GO‐PA nanohybrid as filler

AbstractDespite many important industrial applications, epoxy resin (EP) suffers from high flammability. To solve the problem, functionalized graphene oxide with Co‐MOF and phytic acid (ZIF‐67@GO‐PA) was successfully prepared. Subsequently, 2 wt% of ZIF‐67@GO‐PA nano‐hybrids were added into EP. Base on the fire test results, the limiting oxygen index value of EP/ZIF‐67@GO‐PA enhances to 29.4% and its UL‐94 achieves V‐0 rating. Moreover, compared with pure EP, the peak heat release rate and total release rate are dramatically decreased by 57.4% and 25.7%, respectively. In addition, the fire growth index was reduced by 64.0%. These superior fire safety properties are due to the catalytic effect of metal oxide and phosphorous compounds produced during the combustion of ZIF‐67@GO‐PA, and the barrier effect of the graphene oxide. Because the denser char blocks the diffusion of heat during combustion, the fire hazard of EP composites is reduced.

INVESTIGATION THE FIRE HAZARD OF PLYWOODS USING A CONE CALORIMETER

A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.

Photo‐aging deterioration of hybrid intumescent flame retarding coatings simultaneously modified by silicon aerogel, β‐cyclodextrin, and nano‐ZnO

AbstractPhoto‐aging has been manifested as the main threat to the service performance of organic coatings, but the deterioration of intumescent flame retarding coatings (IFRC) is scarcely reported. Therefore, the finish IFRC is benignly designed by simultaneously incorporating silicon aerogel, β‐cyclodextrin, and nano‐ZnO, its deterioration mechanism under photo‐aging (composed of xenon lamp radiation and water spraying) is quantitatively investigated. The results show that the photo‐aging facilitates the declined flame retardancy, as measured by the rising fire growth index from 1.07 to 2.43 kW m−2·s−1 and the reduced fire performance index from 0.493 to 0.196 s·m2·kW−1 with the flame retardancy index of 0.18 for S30d, as well as the diminished smoke suppression. Because the cleavage of C═N bonding occurs for the IFRC subjected to photo‐aging, presenting the serious yellowing of the IFRC surface with enhanced hydrophilicity. Meanwhile, the light‐humidity cycles of photo‐aging lead to the transformation from glassy residue to crystalline SiP2O7 during firing, presenting the disorder and fluffy char for S30d. Thirdly, the photo‐aging makes the pyrolysis Eα of 370 ~ 320°C drop from 177.9 to 120.2 kJ·mol−1 by the modified Coats‐Redfern integral method. It probes the photo‐aging deterioration mechanism of organic–inorganic hybrid IFRCs.