Reduced Heat Release Research Articles

Synergistic Effects of Diatoms on Intumescent Flame Retardant High Impact Polystyrene System.

In this work, aiming to improve the flame retardancy performance of high impact polystyrene (HIPS), HIPS compounds were synthesized with the addition of intumescent flame retardant (IFR: mass ratio of APP and PER was 3:1) and diatoms into HIPS matrix by melt blending method. It was found the IFR/diatoms system exhibited high flame retardant efficiency and catalytic carbonization effect to HIPS matrix in the burning process. The LOI value of HIPS-2 compound with the addition of 28 wt% IFR and 2 wt% diatoms was increased to 29.0% and passed V-0 rating. The value of PHRR for HIPS-2 compound is about 460.58 kW/m2 compared with 937.22 kW/m2 of pure HIPS and the value of THR for HIPS-2 compound is about 32.9 MJ/m2 compared with 62.7 MJ/m2 of pure HIPS, suggesting that the addition of IFR/diatoms system can decrease the values of PHRR and THR, which shows the synergistic effect between IFR and diatoms on reducing heat release. The 21.9% reduction in Av-EHC and 41.4% reduction in TSP seen on introducing an IFR/diatoms system indicates effective smoke suppression, which potentially would significantly reduce the death rate in real fire accidents. The TG-IR results indicated that the IFR/diatoms flame retardant system functioned in the gas phase to suppress the flame. The SEM images showed the char residue produced was more compact and continuous, which suggests that the IFR/diatoms flame retardant system exhibits barrier and catalytic effects to block heat transferring and promote char forming. The tensile strength and impact strength of HIPS-2 compound were 22.95 MPa and 2.63 KJ/m2, respectively. The tensile strength and impact strength were increased by 34.13% and 19.55% compared with that of pure HIPS.

Polyelectrolyte as highly efficient flame retardant to epoxy: Synthesis, characterization and mechanism

To balance the flame retardancy and mechanical properties of epoxy (EP) resin, a polyelectrolyte complex (PPA-PEI, P content of 9.27%) was facilely prepared in aqueous solution by the neutralization reaction between polyethyleneimine (PEI) and phenyl phosphonic acid (PPA). Just 4 wt% PPA-PEI could endow the relating EP composite with satisfied flame retardancy (limited oxygen index (LOI) of 29.0%, UL-94 V-0 rating). It also shows significant reduction in total heat release (THR), peak heat release (PHRR), total smoke production (TSP) of 52.5%, 52.3%, and 22.7%, respectively. Analyzed from the char morphologies and chemical structures, it can be induced that the good flame retardancy is mainly attributed to the highly yielded char residue with well swelled and multicellular structures possessing good barrier and thermal insulation properties. Meanwhile, the dilution and free radical scavenging effects also work well in the gaseous phase. Before the PPA-PEI molecules start to collapse into cluster seriously to worsen the dispersability within EP matrix, EP/4 wt%PPA-PEI can maintain similar tensile strength and glass transition temperature (Tg), and display improved Yong's and storage modulus compared with neat EP. Accordingly, this presented work provides a low-cost and promising approach for preparing flame-retardant EP/PEC composites with excellent comprehensive performance.

Melamine tannin nanosheet loading on black phosphorus towards enhancing its thermal safety, catalytic smoke and toxicity suppression performances

Black phosphorus (BP) was limited in practical application due to its instability in the air and low compatibility with polymers. In addition, the lack of smoke suppression of BP made it difficult to reduce the harm of smoke and toxic gas in fire. The functional BP nanosheets (BP-TA@MA-Co) were prepared by combining the smoke suppression mechanism of cobalt ions with the oxidation resistance mechanism of melamine tannin nanosheets. Excellent fire safety was clearly demonstrated by the effective combination of BP-TA@MA-Co and epoxy (EP), with 63.5% reduction in total heat release (THR), 18.1% reduction in total smoke production (TSP) and 19.5% reduction in total carbon monoxide. Therefore, this study provided a feasible solution for loading high-valence metal compounds on the surface of BP and a unique thinking for the preparation of EP composites with high comprehensive performances.

Bioinspired multilayer multiscale architectures into PDMS for simultaneously enhancing the thermal conductivity and flame retardancy

Combing high thermal conductivity and excellent flame retardancy is crucial for the development of thermal management composites. Herein, we report a bioinspired multilayer multiscale architecture comprising nanoscale MXene as the protective layer 1, atomic Cu2+ coordination molecular scale dendritic PEI as the protective layer 2 and encapsulated flammable PDMS as a matrix. Upon exposure to flame, the two layers can hinder polymer combustion, wherein MXene nanosheets and PEI-Cu serve as a barrier and thermally conductive layers, as well as catalytic and adsorption layers, respectively. As a result, the as-prepared PDMS composites exhibit a high out-of-plane thermal conductivity of ∼0.60 W m−1k−1, a reduced heat release rate and extremely low smoke (CO and CO2) generation at low filler loadings, suggesting excellent smoke suppression and toxicity reduction. This study provides a new strategy for the development of polymer composites with high thermal management capabilities and excellent flame retardancy.

Efficient flame retardancy, good thermal stability, mechanical enhancement, and transparency of DOPO-conjugated structure compound on epoxy resin

A novel multifunctional flame retardant EAD with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and conjugated structure was successfully synthesized via addition reaction of PH bond and alkynyl group. The structure was characterized by Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance (NMR) spectra. Thermogravimetric analysis (TGA) showed that EAD possessed high thermal stability with 290 ℃ Tonset and 20.4% char yield at 700 ℃ due to the presence of rigid structure and crosslinking reaction. When incorporating 2 wt% EAD into epoxy resin, the results from TGA indicated that the modified sample had good thermal stability with a Tonset value of 354 ℃ and char-forming performance with 22.9% char yield at 700 ℃, as well as glass transition temperature without any deterioration was obtained. Compared with pure epoxy, the same EAD content with only 0.186 wt% phosphorus loading improved effectively the flame retardancy, reflected by the increased limiting oxygen index (LOI) value of 31.0% and V-0 rating in UL-94 vertical burning test. Results from cone calorimeter test (CCT) further confirmed the positive effect on the fire retardancy, which was expressed as the heat release reduction and smoke suppression. The high-efficient flame retardancy was investigated by analyzing the pyrolysis behavior and char residue, which demonstrated the multiple actions of EAD in gas and condensed phases. The low addition of EAD also brought out the reinforcing and toughening effect for epoxy resin. Moreover, the modified epoxy samples with no more than 2 wt% EAD presented good transparency and UV-shielding performance.

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.

Fire Behavior and Failure Model of Multilayered Wood Flour/HDPE/Polycarbonate Composites with a Sandwich Structure.

The flame retardancy of wood–polymer composites significantly affects their potential applications. Thus, multilayered wood flour/high-density polyethylene (HDPE)/polycarbonate (PC) composites were prepared via thermocompression to improve the fire retardancy of wood–polymer composites in this paper. Thermal degradation behavior, flame retardancy, and flexural strengths of the resulting composites were investigated using a thermogravimetric analysis, cone calorimetry, and mechanical testing machine, respectively. Results revealed that the boric acid treatment reduced the heat release rate and total heat release of the wood flour/HDPE composites and increased their mass of residues. However, boric acid reduced the flexural strength of the resulting composites. The combustion test indicated that PC cap layers suppressed the combustion of the resulting composites via the formation of carbon layers. Adding PC layers reduced heat release and increased the flexural strength of the resulting composites. Finally, the failure mode of the multilayered wood flour/HDPE/PC composites in the three-point flexural test was simulated by finite element analysis.

Facile Construction of Polypyrrole Microencapsulated Melamine-Coated Ammonium Polyphosphate to Simultaneously Reduce Flammability and Smoke Release of Epoxy Resin.

A unique mono-component intumescent flame retardant, named PPy-MAPP, of which melamine-coated ammonium polyphosphate (MAPP) was microencapsulated by polypyrrole (PPy), was synthesized and carefully characterized. The obtained PPy-MAPP was applied to epoxy resin (EP) for obtaining flame-retarded EP composites. The results show that PPy-MAPP imparts better flame retardancy and smoke suppression properties to EP compared to the same addition of MAPP. The EP composite with 15 wt% PPy-MAPP easily passes the UL94 V-0 rating and achieves an LOI value of 42.4%, accompanied by a 61.9% reduction in total heat release (THR) and a 73.9% reduction in total smoke production (TSP) when compared with pure EP. The char residue analysis shows that PPy-MAPP can promote a generation of more phosphorus-rich structures in the condensed phase that improve the integrity and intumescence of char against fire. The mechanical test indicates that PPy-MAPP has a less negative effect on the tensile strength and elastic modulus of epoxy resin due to the good compatibility between PPy-MAPP and the EP matrix, as supported by differential scanning calorimetry (DSC) analyses. In this paper, these attractive features of PPy-MAPP provide a new strategy to prepare satisfactory flame retardant and super flame retarding EP composites.

Simultaneous improvements of the fire safety, mechanical properties and water resistance of vinyl ester resin composites by introducing microencapsulated ammonium polyphosphate by polytriazole

Achieving a good balance between mechanical properties and flame retardancy of vinyl ester resin (VER) remains a challenge for traditional inorganic retardants. Herein, a reactive coating shell was constructed on the surface of ammonium polyphosphate (APP) through click chemical reaction. The microencapsulated APP (MAPP) was introduced into and reacted with VER matrix. The coating and the reaction between the filler and the matrix bring a dual effect on comprehensive properties. 10 wt% addition of MAPP not only endow material with better fire safety including a limiting oxygen index of 27.1%, 44% reduction of total heat release, and 38% reduction of total smoke production, but also enhance the flexural and notched Izod impact strength compared with pure VER. The composite exhibits enhanced water resistance, as evidenced by relatively less reduction of flexural strength after immersing in boiling water for 6 h. The dual function enhancement strategy can provide new ideas to prepare composites with balanced flame retardancy, water resistance and mechanical properties.

Rigid polyurethane foam composites based on iron tailing: Thermal stability, flame retardancy and fire toxicity

In order to explore the potential utilization value of iron tailings, the typical solid waste-iron tailings was introduced into rigid polyurethane foam (RPUF) as a flame retardant filler in this paper. The flame retardant performance, combustion performance, gas-phase products and char residue’s related properties of RPUF/ITS composites were systematically investigated by limiting oxygen index, thermogravimetric (TG), cone calorimetry (CCT) and thermogravimetric-infrared spectrometry (TG-FTIR). The results showed that ITS improved the overall thermal stability of the composites, and the T-5%, T-50%, Tmax1, Tmax2 and char residue rates were all higher than those of the pure samples. The CCT indicated that ITS had a certain effect on smoke suppression and heat release reduction. The peak heat release rate of RPUF-6 was reduced by 22.75% compared with that of the pure sample, and the total smoke release of RPUF-2 was reduced by 25.36%. Smoke factor (SF), fire growth rate index and fire performance index indicated that ITS reduced the fire risk of RPUF/ITS composites. TG-FTIR showed that ITS inhibited the decomposition of RPUF/ITS composites, and the release intensity of hydrocarbons, CO2, isocyanate compound, CO, aromatic compounds and esters decreased significantly. TG, MCC, scanning electron microscope and Raman implied that ITS promoted the formation of a dense char layer in RPUF and improved the heat resistance of the char layer.

Interfacial architecting of organic–inorganic hybrid toward mechanically reinforced, fire-resistant and smoke-suppressed polyurethane composites

Polyurethane (PU) composites integrated with outstanding fire retardancy, smoke suppression as well as ameliorated mechanical property is attractive, but remains a challenge. Here, we demonstrate the interfacial architecting of organic–inorganic hybrid (ACAPP) by reacting renewable chitooligosaccharide (COS) with ammonium polyphosphate (APP) and ammonium octamolybdate (AOM) via a one-pot, facile and eco-friendly approach. The ACAPP with multiple hydroxyl groups shows good compatibility and strong interfacial adhesion force with PU matrix due to the abundant covalent cross-linking points and hydrogen bonds networks. The incorporation of 15 wt% ACAPP enables the resultant PU composite to achieve a V-0 rating, a limiting oxygen index of 26.1%, 31.1% and 44.8% reduction in total heat release and total smoke production, respectively, far outdistancing conventional APP. The suppressed fire hazards mainly benefits from the synergy catalytic carbonization effect of ACAPP in condensed phase. Moreover, ACAPP reinforces the tensile strength of PU whilst retaining the decent ultimate elongation. This work may offer a referable exemplification for constructing green flame-retardant to balance high fire safety and mechanical properties.

Microfibrous cyclodextrin boosts flame retardancy of poly(lactic acid) II - phosphorous silane treatment further enhances the effectivity

Recently, the flame retardant effectiveness of a 2-hydroxypropyl-β-cyclodextrin (CD) type bio-based carbonising agent has been evinced to noticeably increase when used in a microfibrous form, as obtained by electrospinning method. In the present research, the flame retardant performance of the electrospun CD was further enhanced by reactive surface modification with a phosphorous silane (PSil) compound. Surface-treated and untreated CD-based carbonising agents were compared, both in powder and in microfibrous form, besides ammonium polyphosphate (APP) to form an intumescent flame retardant system for poly(lactic acid) (PLA). The Limiting Oxygen Index (LOI) of the flame-retarded PLA composites increased outstandingly, from 25.0% (corresponding to the 15 wt% APP containing PLA) to as high as 37.5%, as a result of adding only 3 wt% of PSil-treated microfibrous CD to the system. Also, the main combustion characteristics improved; compared to neat PLA, about 50% reduction in the peak heat release rate (pHRR) and 25% reduction in total heat release (THR) were achieved, accompanied by an increased amount of char residue after combustion. The beneficial effect of the PSil-treated CD microfibre relies mainly on its enhanced physical and chemical interaction with APP and its increased charring ability and thermal stability, which contribute to the formation of a fire protecting char of increased structural integrity.

Flammability and thermal stability of thermoplastic-based composites filled with natural carbon

This investigation characterized flammability and thermal stability for a novel sustainable composite engineered for use in building applications. Flammability and thermal stability of coal plastic composites composed of coal (40–60 wt.%) and high-density polyethylene were compared to commercial wood–plastic composites. Pyrolysis thermogravimetric analysis results indicated that coal plastic composites possessed a single-step decomposition and higher char residue, while wood–plastic composites had two-step decomposition, with the first peak occurring at much lower temperatures. Thermogravimetric analyses in air suggest coal plastic composites, compared to wood–plastic composites and neat high-density polyethylene, were more thermally stable. Flash ignition temperatures for coal plastic composites were higher than high-density polyethylene and wood–plastic composites, while self-ignition temperatures were in the same range as wood–plastic composites. Rate of burning data indicated coal plastic composites were slower burning than wood–plastic composites, with increasing coal content slowing burning rate by 19.9%–27.6%. Cone calorimeter testing showed 27% and 59% reduction in total heat release and total smoke release as coal content increased while coal plastic composite with 60 wt.% coal possessed lower overall flammability in comparison with predominant commercially available wood–plastic composite products. Coal improved composite overall thermal stability and flammability by acting as char former and foaming agent.

Boosting safety and performance of lithium-ion battery enabled by cooperation of thermotolerant fire-retardant composite membrane and nonflammable electrolyte

• Thermotolerant and fire-retardant nano-CaCO 3 -based membrane was designed. • LIBs with nonflammable electrolyte-immersed membrane possess superior cyclability. • LIBs exhibit better safety by preventing short circuit and reducing heat release. • Lithium ion full battery shows good long cycling stability at 120 °C under 2C. Developing nonflammable electrolytes is regarded as a convenient strategy to solve the combustion problem of lithium-ion batteries (LIBs), but its influences are limited by the severe shrinkage and high combustibility of polyolefin separators at elevated temperatures. Herein, an intrinsically thermotolerant and fire-resistant nano-CaCO 3 -based composite membrane (CPVH) is designed rationally. The CPVH membrane presents superior thermal stability (barely visible shrinkage at 300 °C), excellent nonflammability and extremely low heat release (∼11% as much as PP). Moreover, the alkaline nano-CaCO 3 can neutralize hydrofluoric acid that inevitably exists in LiPF 6 -based electrolytes, guaranteeing the long-term stability of interfacial layers. Noticeably, LiFePO 4 /Li battery with CPVH membrane delivered a discharge capacity of 133.6 mAh g −1 at 0.5C, along with a capacity retention of 93.0% and a coulombic efficiency of 99.9% after 650 cycles. Additionally, harsh safety tests of the battery demonstrate stable circuit safety at a high temperature of 150 °C and a significantly low heat release during thermal runaway. Significantly, the LiFePO 4 /CPVH/graphite full battery showed good cycling stability with a capacity retention of 78.4% and an average coulombic efficiency of 98.0% at 120 °C and 2C after 100 cycles. By combining CPVH composite membrane and nonflammable electrolyte, both safety and cycling performance of LIBs were improved completely.

Electromagnetic Shielding and Flame Retardancy of Composite Films Constructed with Cellulose and Graphene Nanoplates.

Aimed at improving the electromagnetic (EM) shielding and flame retardancy of cellulose materials, graphene (GE) nanoplates were introduced into cellulose matrix films by blending in 1-allyl-3-methylimidazolium chloride. The structure and performance of the obtained composite films were investigated using scanning electron microscopy, X-ray diffraction, thermogravimetric (TG) analysis, EM shielding effectiveness (SE), and combustion tests. GE introduction formed and stacked laminated structures in the films after drying due to controlled shrinkage of the cellulose matrix. The lamination of GE nanoplates into the films was beneficial for providing EM shielding due to multiple internal reflection of EM radiation; furthermore, they also increased flame resistance based on the “labyrinth effect.” The SE of these composite films increased gradually with increased GE content and reached 22.3 dB under an incident frequency of 1500 MHz. TG analysis indicated that these composite films possessed improved thermal stability due to GE addition. Reduced flammability was confirmed by their extended times to ignition or inability to be ignited, reduced heat release rates observed in cone calorimetry tests, and increased limiting oxygen index values. These films with improved EM shielding and flame retardancy could be considered potential candidates for multipurpose materials in various applications, such as electronics and radar evasion.

Synthesis of low phosphorus flame retardant containing benzimidazole and hydroxyl and its application in reducing combustion smoke for epoxy resin

AbstactIn this work, an economic and environmentally friendly phosphorus‐nitrogen‐based flame‐retardant containing benzimidazole structure and hydroxyl group (DOPO‐BHM) was successfully synthesized by a simple two‐step procedure. The as‐prepared DOPO‐BHM was characterized by1H NMR,31P NMR, and FTIR, and incorporated into epoxy matrix as co‐curing agent to remarkably improve the flame retardancy of epoxy resin (EP). When the amount of DOPO‐BHM in EP was 6% and the phosphorus content was as low as 0.408%, the EP/DOPO‐BHM composites achieved a high limiting oxygen index (LOI) of 32.7% and V‐0 vertical firing grade. Furthermore, the cone calorimeter (CC) test results showed that the values of total heat release (THR), heat release rate (HRR), total smoke production (TSP), and smoke production rate (SPR) of EP/6% DOPO‐BHM decreased by 12.9%, 28.5%, 30.0%, and 47.8% relative to EP, respectively, indicating that the modified EP had good performance of reducing heat release and inhibiting smoke release. In addition, FTIR, Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) were carried on to understand the flame retardancy mechanism. The characterizations indicated that the flame retardancy effect of DOPO‐BHM was in both condensed and gaseous phase, and gaseous phase played a dominant role. In addition, the mechanical test results showed that the tensile strength, bending strength, and non‐notched impact strength of EP/6% DOPO‐BHM were improved to a certain extent. In summary, DOPO‐BHM could significantly improve the flame retardant effect of EP without loss of mechanical properties and reduce emissions of phosphorus and smoke.

Facile construction of flame‐retardant, heat‐insulating agar/polyvinyl alcohol composite aerogels via in situ formation of magnesium hydroxide and palygorskite‐assisted strategy

AbstractNatural polymer aerogel is a candidate material with broad application prospects in the field of building insulation because of its lightweight, low thermal conductivity, and biodegradability. However, poor mechanical properties and easy combustion greatly limit its development. In this work, magnesium hydroxide (MH) was synthesized in situ in the agar (AG)/polyvinyl alcohol (PVA) composites using magnesium oxide as raw material. Furthermore, the one‐dimensional rod‐like nanoclay palygorskite (Pal) was introduced into the composites. A series of composite aerogels with different ratios of MH and Pal were prepared by a simple freeze‐drying process, and their microstructure, mechanical properties, water resistance, thermal stability, thermal insulation, and flame‐retardant properties were investigated. Cone calorimeter tests showed that MH/Pal synergistic flame retardant had excellent performance in reducing heat release rate and suppressing smoke. The AG/PVA/MH/Pal composite samples had a limiting oxygen index of 37.5% and achieved V‐0 rating in the UL‐94 test. In addition, the introduction of MH and Pal has enabled the AG/PVA composite aerogels to exhibit superior mechanical, thermal insulation, and water stability properties.

Biobased alginate treatments on flax fibre reinforced PLA and PHBV composites

This paper presents a novel study on the effect of alginates as a compatibilizer and flame retardant in natural fibre reinforced PLA and PHBV composites. Though alginates have been extensively studied for biomedical applications it's potential as a bio-based compatibilizer and flame retardant in biocomposites has not been investigated. In this study, flax nonwovens were treated with alginate solution and composites were prepared by casting technique and compression molding using chemically modified and unmodified flax nonwovens and biopolymers such as poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV). The developed composites were subjected to dynamic mechanical and thermal analysis. The fire resistance of the treated and untreated flax fibres were also tested using a cone calorimeter. Composites containing alginate modified flax fibres were found to exhibit improved viscoelastic and thermal properties. The storage modulus of alginate modified flax reinforced PLA samples exhibited a 60% increment compared to unmodified samples. Alginate modified flax fabrics exhibited reduced heat release rate values and smoke release rates when compared to untreated flax fabrics. Alginates showed potential for use as environmentally friendly compatibilizers and smoke suppressors in natural fibre composites for the development of completely sustainable and biodegradable composites.

Plasma-Ozone Treatment of Air Supply on Performance and Emissions of Diesel Engine

In improving performance and reducing exhaust emissions in combustion engines, the addition of ozone to the air supplied in the combustion chamber was studied. In this research, ozone can be produced using plasma technology (plasma-ozone) which is a simple and eco-friendly technology. Plasma-ozone was generated using the Dielectric Barrier Discharge (DBD) method. Air is passed in plasma-ozone reactors at different voltages with an ozone variation of 3 mg, 12 mg, 15 mg and 18 mg is obtained. Ozone concentration was detected using an Ozone meter O3 Air Quality Detector and OPA-100 was used to determine exhaust emissions. The result showed that the addition of ozone to the air supply has no significant effect on brake power but is able to increase specific fuel consumption, increase cylinder pressure, shorten combustion processes, and reduce heat release values. The addition of ozone decreases the opacity of exhaust emissions in TV-1 diesel engines become more eco-friendly.

Fire Resistance, Thermal and Anti-Ageing Properties of Transparent Fire-Retardant Coatings Modified with Different Molecular Weights of Polyethylene Glycol Borate.

Four kinds of polyethylene glycol borate (PEG-BA) with different molecular weights were grafted into cyclic phosphate ester (PEA) to obtain flexible phosphate esters (PPBs), and then applied in amino resin to obtain a series of transparent intumescent fire-retardant coatings. The comprehensive properties of the transparent coatings containing different molecular weights of PEG-BA were investigated by various analytical instruments. The transparency and mechanical analyses indicate that the presence of PEG-BA slightly decreases the optical transparency of the coatings but improves the flexibility and adhesion classification of the coatings. The results from fire protection and cone calorimeter tests show that low molecular weight of PEG-BA exerts a positive flame-retarded effect in the coatings, while high molecular weight of PEG800-BA behaves against flame-retarded effect. Thermogravimetric and char residue analyses show that the incorporation of low molecular weight of PEG-BA clearly increases the thermal stability and residual weight of the coatings and generates a more compact and stable intumescent char on the surface of the coatings, thus resulting in superior synergistic flame-retarded effect. In particular, MPPB1 coating containing PEG200-BA exerts the best flame-retarded effect and highest residual weight of 36.3% at 700 °C, which has 57.6% reduction in flame spread rate and 23.9% reduction in total heat release compared to those of MPPB0 without PEG-BA. Accelerated ageing test shows that low molecular weight of PEG-BA promotes to enhance the durability of structural stability and fire resistance of the coatings, while PEG800-BA with high molecular weight weakens the ageing resistance. In summary, the fire-resistant and anti-ageing efficiencies of PEG-BA in the coatings depend on its molecular weight, which present the order of PEG200-BA > PEG400-BA > PEG600-BA > PEG800-BA.