Limiting Oxygen Index Test Research Articles

In situ self-assembly of zeolitic imidazolate frameworks on the surface of flexible polyurethane foam: Towards for highly efficient oil spill cleanup and fire safety

In this work, a hydrophobic and oleophilic flexible polyurethane foam modified with metal organic framework (MFPU) was successfully fabricated through in situ self-assembly method. The structure and morphology of MFPU foams were characterized by X-ray diffraction, Fourier transform infrared spectra, Scanning electron microscopy and Energy dispersive X-Ray spectroscopy measurements. The growth of metal organic frameworks improved the surface roughness of FPU foams, leading to the highly increased water contact angle, which could provide well ameliorated hydrophobicity and lipophilicity properties. The modified FPU foams exhibited extraordinary absorption capacity and recyclability for various kinds of oils and organic solvents. The maximum absorption capacity could achieve 33 times of its own weight. The flammability of MFPU foams was evaluated by cone calorimeter test, vertical burning test and limited oxygen index test, the peak heat release rate and smoke production rate both decreased dramatically, indicating the coating of ZIF-8 was significantly conducive to improve the flame retardancy of FPU foams. These improvements made MFPU foams become an excellent absorbent with remarkable fire safety, and offered it with potential application in oil/water separation.

Effect of different ionic layered compounds decorated with zinc hydroxystannate on flame retardancy and smoke performance of epoxy resin

ZHS@ Mg‐Al‐LDH and ZHS@α‐ZrP hybrid materials were prepared by electrostatically loading zinc hydroxystannate (ZHS) on the layered compounds (Mg‐Al‐LDH and α‐ZrP) in this work. With the addition of 2 wt% of the two hybrid materials to epoxy resin (EP), respectively, the fire hazard of EP and its composites were investigated. The limiting oxygen index (LOI) of ZHS@ Mg‐Al‐LDH/EP composite increased by 19.0% compared with pure EP, while its peak heat release rate (PHRR), total heat release rate (THR), and peak smoke release rate (SPR) decreased by 48.2%, 20.8%, and 21.6%, respectively, evidenced by the results of the LOI test and cone calorimetry test (CCT). The LOI of ZHS@α‐ZrP/EP composite increased by 20.4%, and its PHRR, THR, and SPR decreased by 47.7%, 21.4%, and 27.1%, respectively. Both hybrid materials showed prominent flame retardant and smoke suppressing properties. In addition, through the analysis of the TG‐IR and Raman spectrum of residual char, the specific mechanism of flame retardance and smoke suppression was explored.

Effects of alumina trihydrate (ATH) and organic montmorillonite (OMMT) on asphalt fume emission and flame retardancy properties of SBS-modified asphalt

The objective of this study was to evaluate the flame retardancy and emission properties of asphalt binders containing ATH and OMMT. Limit oxygen index test was performed to evaluate the flame retardancy of each asphalt binder. Volatile organic compound (VOC) emission properties of the asphalt mixture in the mixing process were investigated using a designed test method. Thermogravimetry and Fourier transform infrared spectroscopy were used to evaluate the thermal stability and volatile-release properties of the asphalt binders. The results indicated that both ATH and OMMT effectively suppress the VOC release of the modified asphalt. The flame retardancy and VOC-emission properties of the OMMT/ATH modified asphalt were significantly improved. The addition of ATH/OMMT delayed the thermal decomposition and exhibited good thermal-insulation performance, reducing the heat release during asphalt combustion. Additionally, The ATH/OMMT compounds prevented the breakage of molecular chains in the asphalt, promoting the charring of the asphalt during combustion. According to the engineering-property tests of modified asphalt mixtures, the ATH/OMMT significantly improved the high-temperature performance of the asphalt mixture. However, it slightly reduced the thermal-cracking resistance and moisture susceptibility of the asphalt mixture.

Preparation of hexakis (4‐aldehyde phenoxy) cyclotriphosphazene grafted kaolinite and its synergistic fire resistance in poly (butylene succinate)

AbstractHexakis (4‐aldehyde phenoxy) cyclotriphosphazene (HAPCP) was synthesized firstly and then it was grafted onto the exfoliated kaolinite (Kaol) to prepare K‐HAPCP. The structure of HAPCP and K‐HAPCP was well characterized. K‐HAPCP was used as synergistic agent in poly (butylene succinate) (PBS)/intumescent flame retardants (IFR) composites. The combustion behavior of PBS composites was reflected by limited oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter test. The thermal stability was traced by thermogravimetric analysis. PBS is highly flammable with the LOI value of only 21.9% and cannot pass any UL‐94 grade during vertical burning test. By the presence of 22 wt% IFR and 3 wt% K‐HAPCP, the LOI of PBS composite is sharply increased to 40.3% and the sample can pass UL‐94 V‐0 rating with excellent anti‐dripping properties. Moreover, the degradation behavior is investigated and the probable flame retardant mechanism is also proposed.

Microscopy as a tool to investigate the influence of ammonium polyphosphate particle size on the flame retardant properties of polymer composites

The influence of ammonium polyphosphate (APP) particle size on the performance of an intumescent formulation and on the synergistic action of a series of montmorillonite samples with different d-spacings for the production of flame retardant composites was investigated. The polymer matrix employed was poly(ethylene-co-butyl acrylate), EBA 30, and the intumescent formulation consisted of APP and pentaerythritol (PER). After being processed, the composites were submitted to scanning electron microscopy (SEM), thermogravimetric analysis, heating microscopy, and limiting oxygen index tests. The results indicate that the greater interaction between the APP and PER molecules, caused by the increase of the contact area promoted by the reduction of the APP particle size, could favor the esterification reaction between APP423 and PER, allowing the formation of a greater amount of char precursors in shorter period of time. In addition, the montmorillonite d-spacings had a more pronounced influence on the clays synergistic action with the intumescent formulation containing the APP with smaller particle size. Microscopy has shown to be an important tool to investigate APP particle size effect on the fire retardancy. AFM results enabled the detection of nanometric particles in the sample containing the smallest particle size of APP. SEM micrographs showed that those nanometric particles were better dispersed in the matrix, interacting more effectively with the other components, a factor probably responsible for the superior fire retardancy results. Heating microscopy revealed that the material with smaller APP particle size did show some remaining structure at the temperature of 850°C.

Synthesis of a novel phosphorus-nitrogen flame retardant and its application in epoxy resin

A novel phosphorus-nitrogen flame retardant named as melamine phenyl phosphate (MAPPO) was synthesized successfully via the neutralization reaction between phenylphosphonic acid (PPOA) and melamine (MA). The chemical structure of MAPPO was characterized by Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR) and element analysis (EA). MAPPO was introduced into epoxy resin by blending to improve the flame retardancy. Flame retardancy and combustion behavior of EP/MAPPO were investigated by limiting oxygen index (LOI) test, vertical burning (UL-94) test and cone calorimeter test. UL-94 and LOI tests results showed EP containing 18 wt% MAPPO passed the UL-94 V-0 rating and got a high LOI value of 33%. In the cone calorimeter test, compared with that of EP, the values of peak of heat release rate (HRR), total heat release (THR), peak of smoke production rate (PSPR) and total smoke production (TSP) of modified EP were reduced by 58.7%, 40%, 49% and 61.6%, respectively. By analyzing the volatile pyrolysis products of MAPPO, it was known that MAPPO mainly produced CO2, NH3, H2O and other nitrogen-containing compounds, which diluted the concentration of fuel gases and oxygen during combustion. Meanwhile, the char residue of EP/MAPPO system after combustion was also analyzed by scanning electron microscope (SEM), FT-IR and Raman tests, and the results showed MAPPO was able to promote the crosslinking of EP leading to the formation of compact char layer containing P–O–C, PO and CC, etc. In a word, the enhancement in flame retardancy was attributed to both dilution effect of non-combustible gases and barrier effect of compact char.

The synergistic effect of organic montmorillonite and thermoplastic polyurethane on properties of asphalt binder

This paper aims at investigating the synergistic effect of organic montmorillonite (OMMT) and thermoplastic polyurethane (TPU) on physical and rheological properties of asphalt binder. Herein, the structure and content of OMMT and TPU in asphalt binder were first determined. OMMT/TPU modified asphalt binders were then evaluated by XRD (X-ray diffraction), FTIR (Fourier transform infrared), penetration, softening point, ductility, viscosity, storage stability, DSR (dynamic shear rheometer), BBR (bending beam rheometer) and LOI (limiting oxygen index) tests. Results show that, the increase of OMMT content facilitates storage stability of OMMT/TPU modified binder. Existence of OMMT and TPU with appropriate contents is able to enhance high and low temperature properties, elastic behavior and flame retardancy of asphalt binder. TPU content is the dominant factor of low temperature property, while OMMT content plays a key role in flame retardancy of OMMT/TPU modified binder. Additionally, it is recommended to use 2% OMMT and 9% TPU in asphalt binder. All in all, OMMT and TPU present a good synergy in asphalt matrix.

Highly effective flame‐retarded polyester diol with synergistic effects for waterborne polyurethane application

ABSTRACTIn this article, a novel bi‐reactive flame retardant (FRD) was successfully synthesized for waterborne polyurethane (WPU). The chemical structures of FRD were characterized by Fourier‐transform infrared spectra and 1H and 31P nuclear magnetic resonance. Then, the FRD was incorporated into polyurethane backbone to prepare a series of flame‐retarded WPU (FRWPU). The flammability characteristics of FRWPU were measured by limited oxygen index (LOI), UL‐94, and cone calorimeter (CCT) tests. The FRPWU‐7 had a high LOI value of 30.5% with UL94 V‐0 rating. Moreover, the CCT values indicated that FRD induced the gaseous phase quenching effect of phosphorus‐containing free radicals derived from the decomposed phosphaphenanthrene group on the gas‐phase flame retardancy. Scanning electron micrographs and Raman spectra exhibited that FRD promoted the charring formation of phosphorus‐rich char layer with graphitized surface and honeycomb‐like intumescent structure in WPU matrix during burning. This study provides a new way to design a novel reactive P–P flame retardant consisted of the phosphaphenanthrene group and intumescent flame retardant for WPU application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48444.

Thermal and Mechanical Behavior of Wood Plastic Composites by Addition of Graphene Nanoplatelets.

Wood plastic composites (WPCs) incorporating graphene nano-platelets (GNPs) were fabricated using hot-pressed technology to enhance thermal and mechanical behavior. The influences of thermal filler content and temperature on the thermal performance of the modified WPCs were investigated. The results showed that the thermal conductivity of the composites increased significantly with the increase of GNPs fillers, but decreased with the increase of temperature. Moreover, thermogravimetric analysis demonstrated that coupling GNPs resulted in better thermal stability of the WPCs. The limiting oxygen index test also showed that addition of GNPs caused good fire retardancy in WPCs. Incorporation of GNPs also led to an improvement in mechanical properties as compared to neat WPCs. Through a series of mechanical performance tests, it could be concluded that the flexural and tensile moduli of WPCs were improved with the increase of the content of fillers.

Eco-friendly flame retardant coating deposited on cotton fabrics from bio-based chitosan, phytic acid and divalent metal ions

With the increasing awareness of environmental protection, the greening of flame retardants has become an inevitable choice for flame retardant technology. Bio-based materials have the advantages of wide source, recyclability and green environmental protection, and have received extensive attention. In this work, chitosan and phytic acid as intumescent flame retardant system and metal ion as a synergist were built on cotton fabrics to achieve efficient flame retardancy by facile dip-pad-dry process. Microscale combustion calorimetry results manifested that the heat release rate values of coated samples were lower than that of uncoated samples. The peak heat release rate and total heat release of uncoated samples were 333.1 W/g and 13.1 kJ/g, while these values of samples coated CH/PA/Ba/PA were 129.1 W/g and 5.4 kJ/g respectively and char residues also were increased sharply owing to the phosphate groups promote the formation of char layer covering the surface of the cotton fabrics, which can prevent heat transfer. Scanning electron microscopy confirmed that there were much more bubbles on the surface of fibers for the coated CH/PA/Ba/PA after horizontal flame tests. The results indicated that the synergy of the intumescent flame retardant system was achieved by the addition of metal ions which could accelerate the produce of a large number of nonflammable gases. Horizontal flame test and limit oxygen index (LOI) test showed that the burning rate and LOI values of samples coated CH/PA/Ba/PA, CH/PA /CH/PA, PA/Ba/PA/Ba were 1.5 mm/s and 22.0, 2.0 mm/s and 20.2 and 2.5 mm/s and 18.0 respectively, compared to 3.3 mm/s and 16.2 of uncoated samples. The samples with intumescent flame retardant system and metal ions (CH/PA/Ba/PA) had best flame retardant performance. Moreover its weight gain (5.2%) was less than that (10.7%) of the sample only with intumescent flame retardant system (CH/PA /CH/PA). The less weight gain had less effect on the softness of cotton fabrics. As a result, the coating is expected to be applied in practice.

Mechanical property improvement and fire hazard reduction of ammonium polyphosphate microencapsulated in rigid polyurethane foam

ABSTRACTAmmonium polyphosphate (APP) is an effective phosphorus‐containing flame retardant. But APP also has excellent hygroscopic capacity and decreases the mechanical property of composite. The aim of the study was to microencapsulate APP with polymethyl methacrylate (PMMA) to prepare microencapsulated ammonium polyphosphate (PMAPP) in order to eliminate the harmful effects caused by the mechanical property of composite. The microcapsules are characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and hydroscopicity test and observed by scanning electron microscopy (SEM). Fire hazard of rigid polyurethane foam (RPUF) is evaluated using a cone calorimeter and limited oxygen index test. The mechanical property of RPUF is studied by compressive strength test. The results show that APP has been microencapsulated by PMMA successfully and the shell does not decrease the beneficial effect of APP on fire hazard of RPUF. Furthermore, the shell also reduces the damage of APP on the mechanical property of composite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48307.

Flame retardancy of epoxy resin nanocomposite with a novel polymeric nanoflame retardant

A wrapped nanoflame retardant, designated as polyhedral oligomeric silsesquioxane (POSS)‐poly(4‐bromostyrene) (PBS)‐carbon nanotubes (CNTs), was synthesized via π‐π stacking interactions between the walls of multiwalled carbon nanotubes and the silicon‐bromine containing hybrid copolymer (designated as POSS‐PBS) that was copolymerized by 4‐bromostyrene and acryloyloxyisobutyl polyhedral oligomeric silsesquioxane. The POSS‐PBS‐CNTs exhibited good dispersibility in epoxy resin (EP) without obvious aggregation. Furthermore, the fire behaviors of this flame‐retardant EP (FR‐EP) nanocomposites were examined via limited oxygen index (LOI) and cone calorimeter (CONE) tests. The FR‐EP had an ideal LOI value of 35.3% and its residual char yield obtained from CONE test was significantly enhanced from 5.9% to 15.3% with the incorporation of 4 wt% POSS‐PBS‐CNTs and 1.33 wt% Sb2O3 into EP matrix. Additionally, the addition of 4 wt% POSS‐PBS‐CNTs or POSS‐PBS can efficiently decrease the peak heat release rate (PHRR) of EP matrix by 41.0% or 45.6%, respectively.

Combined effects of layered nanofillers and intumescent flame retardant on thermal and fire behavior of ABS resin

ABSTRACTThe application of acrylonitrile‐butadiene‐styrene (ABS) copolymer as construction material is largely restricted by its inherent flammability and the release of a great amount of smoke and toxic gases during combustion. To address this issue, the combination of conventional flame retardants and nanoadditives was proven to be a promising way. Herein, both intumescent flame retardants (IFR) and layered nanofillers, that is, graphene and layered double hydroxide were added into ABS resin. These nanofillers exhibited superior dispersion in the ABS matrix. Thermal and fire behaviors of ABS resin were investigated by thermogravimetry analysis, UL‐94 vertical burning test, limiting oxygen index test, and cone calorimetry. The ABS composites containing IFR and layered nanofillers presented remarkable decline in total heat release, peak heat release rate, and volume of toxic effluents released in the burning process compared with those of neat ABS, indicating the significantly improved fire safety of ABS. Moreover, introducing layered nanofillers could further enhance the heat stability and fire safety of the flame‐retardant ABS composites, indicating the presence of synergistic effect between IFR and layered nanofillers. The scanning electron microscopy and Raman spectroscopy results confirmed the formation of compact and dense intumescent chars, which could obstruct the spread of heat and mass, and thus improved the heat stability and flame retardancy of ABS resin. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48220.

Retarding the flammability of polypropylene based on the synergistic effect of montmorillonite and carbon nanotubes

The aim of this work is to reduce the flammability of polypropylene (PP) materials which are plenty used in a variety of industrial applications. For the first time, the efficiency of eco-friendly and low-cost flame retardant of CNTs prepared from rice straw on the flammability degree of PP/MMt composite is reported in this study. Mixtures of polypropylene/ montmorillonite /carbon nanotubes (PP/MMt/CNTs) were prepared by using different percentages of MMt and CNTs. The used CNTs sample was prepared from rice straw waste and the MMt was collected from Wadi El Hamadia, Egypt. The prepared samples were characterized by using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM), while the flammability properties were measured by using Limiting Oxygen Index (LOI). The results of FTIR and the photos of SEM showed that the MMt/CNTs composition is incorporated into the PP matrix. The LOI test revealed that LOI value of PP increased from 18.8% to 21.5 % in presence of MMt particles while the addition of 0.05 and 0.1 % of CNTs to PP/MMt significantly improved the LOI value to become 22.4 and 23.5%, respectively. This finding indicates that the addition of CNTs as co-nanofiller can improve the flame retardancy of PP/MMt composites. Thus the obtained MMt/CNTs composites act as synergist fillers to offer admirable and fire safe PP products.

Dithiocyanurates and thiocyamelurates: Thermal thiyl radical generators as flame retardants in polypropylene

A series of aliphatic and aromatic dithioethers of s-triazine and thioethers of s-heptazines were incorporated into polypropylene and their effectivity as flame retardants was analyzed using a limiting oxygen index (LOI) test, a DIN 4102-1 B2 test, thermogravimetric analyses coupled with mass spectrometry (TGA-MS) and FTIR coupled gas phase analysis (EGA-FTIR). Four symmetric s-triazine disulfides of the type (RSS)3C3N3 - namely 2,4,6-tris(phenyldithio)- (2), 2,4,6-tris(para-tolyldithio)- (4), 2,4,6-tris(octyldithio)- (8) and 2,4,6-tris(dodecyldithio)-1,3,5-triazine (10) - as well as five symmetric s-heptazine sulfides of the type (RS)3C6N7 - namely 2,5,8-tris(phenylthio)- (3), 2,5,8-tris(para-tolylthio)- (5), 2,5,8-tris(1,3-benzothioazol-2-yl)- (6), 2,5,8-tris(iso-propylthio)- (7) and 2,5,8-tris(octylthio)-s-heptazine (9) - were studied. The syntheses of 6, 7, 8 and 9 are reported for the first time. All compounds were analyzed by 1H and 13C NMR spectroscopy, FTIR and elemental analysis. The molecular structure of 7 was determined by single crystal XRD. Beside the flame retardant tests, the fluorescence of 3, 5 and 6 in powder form and when incorporated into polypropylene was measured.In the LOI test, the disulfides of s-triazine are more effective flame retardants than previously known organic disulfides studied in polypropylene.

Synthesis of a hyperbranched phosphorus-containing polyurethane as char forming agent combined with ammonium polyphosphate for reducing fire hazard of polypropylene

Due to the inherent flammability of polypropylene (PP), it is limited in the application of flame retardant materials. In this work, a novel char forming agent, hyperbranched phosphorus-containing polyurethane (HPPU), was synthesized and used as efficient char forming agent. When ammonium polyphosphate (APP) was combined with HPPU, APP/HPPU endow PP significantly improved flame retardancy than single APP. Although the total carbon monoxide production (TCOP) of some PP/APP/HPPU composites is higher than that of PP/APP composite, it is still lower than that of neat PP. LOI (limited oxygen index) and UL-94 tests reveal that PP composites with 25 wt% HPPU/APP with ratio of 4:1 are able to reach 27 vol% and V-0 rating, respectively. The addition of 25 wt% APP/HPPU with ratio of 2:1 into PP can result in decrease in peak heat release rate of about 72%, decrease in total heat release of about 38% and decrease in TCOP of about 93%. APP/HPPU promotes PP to form more stable, compact, and continuous char layer which effectively hinder heat and oxygen transfer and protect the inner matrix from decomposition. Thermogravimetric-infrared results reveal that the gas phase flame retardant mechanism of APP/HPPU is the dilution effect of ammonia from APP and the flame inhibition effect of phosphorus-containing species from HPPU.

Synthesis of a multifunctional bisphosphate and its flame retardant application in epoxy resin

A spiro-bisphosphate (MFR) was designed and synthesized via the reaction of spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) and 2,4-dihydroxybenzophenone (UV-0) with dual functions of flame retardance and ultraviolet absorption. The chemical structure was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The flame retardancy performance of MFR was investigated in the commercial epoxy resin E−44 with respect to pyrolysis and fire behavior by thermogravimetric analysis (TGA), limiting oxygen index test (LOI), vertical burning test (UL 94) and cone calorimeter test. The results showed that EP/20%MFR thermoset (EP thermoset with 20 wt% MFR adding) passed the V-0 level in UL 94, and attained a LOI value of 32.2%. The peak heat release rate (p-HRR), total heat release (THR), average effective heat combustion (av-EHC), average mass loss rate (av-MLR) and total smoke release (TSR) of EP/20%MFR thermoset decreased compared with those of neat EP. The flame retardant mechanism of EP/MFR thermoset has been studied in detail. Adding MFR significantly increased char residues and mainly be responsible for the good flame retardancy of MFR. Besides, MFR demonstrated the better UV absorption capability than UV-0.

Impact of inclusion graphene oxide nanosheets on polystyrene properties

A graphene oxide (GO) was produced for upgrading the thermal stability, flammability and decrease in the fire hazards of polystyrene (PS). Cone calorimeter and limiting oxygen index tests were utilized to assess the heat and flame tests of PS nanocomposites. The addition of GO in PS matrix efficiently improved the flame retardancy and reduced the density of carbon monoxide (CO) release, which attributed to the homogeneous dispersal of GO in the PS matrix upgraded barrier effect that reduced peak heat release rate, total heat release and toxic gas evolution during combustion. The characterization implied that the GO nanosheets were well distributed throughout the PS matrix without clear aggregates, leading to outstanding upgrading of thermal stability and fire safety properties. Dynamic mechanical analysis (DMA) showed that both the storage modulus and glass transition temperature (Tg) of PS/GO nanocomposites were significantly promoted related to that of pristine PS. Moreover, PS/GO nanocomposites clearly decreased the amount of flammable volatiles and CO evolved, suggesting suppressed fire hazards of the PS composites owing to proper distribution, physical barrier effect intumescent and loosely structure of char layers. This study provides useful insights into the flammability behavior of polystyrene compounds with layered fillers of GO.

Synergistic flame-retardant effects of ammonium polyphosphate and AC-Fe2O3 in epoxy resin

The synergistic flame-retardant and smoke suppression properties of ammonium polyphosphate (APP) and activated carbon-supported Fe2O3 (AC-Fe2O3) on flame-retardant epoxy resin (EP) composites were studied. The fire behavior and smoke emission of EP composites were evaluated by limiting oxygen index (LOI), scanning electron microscopy, UL-94 vertical burning, and cone calorimeter test. LOI and UL-94 tests showed that the addition of appropriate amount of AC-Fe2O3 can effectively reduce the fly ash phenomenon, the dripping, and after-flame time. The thermogravimetric analysis and derivative thermogravimetry results showed that APP and AC-Fe2O3 can effectively decrease the maximum decomposition rate (Rmax) and promote the carbonization reaction of EP. As for the cone calorimeter test results, APP and AC-Fe2O3 clearly changed the decomposition behavior of EP, leading to the formation of a stable char layer on the surface of the composites. When flame-retardant loading was 4 mass%, the peak heat release rate and peak smoke production rate of the 3APP/1AC-Fe2O3/EP sample decreased 50.2% and 46.9%, respectively. The amount of char residual after test increased from 8.47 to 21.25%. In addition, it was observed from the macroscopic photographs of the char residue after the cone test that, at the optimum proportion, APP and AC-Fe2O3 could promote the formation of compact charred layers and prevent their cracking, which effectively protected the underlying materials from burning.

Analysis of thermal stability and pyrolysis kinetic of dibutyl phosphate-based ionic liquid through thermogravimetry, gas chromatography/mass spectrometry, and Fourier transform infrared spectrometry

To analyze the feasibility of phosphorus-containing ionic liquids used as flame retardants on flammable materials, thermal stability and pyrolysis kinetics of 1-butyl-3-methylimdazolium dibutyl phosphate ([Bmim][DBP]) were investigated using nonisothermal thermogravimetry. The apparent onset decomposition temperature (T0) and mass fraction of residual carbon were 275.2–297.3 °C (± 0.5 °C) and 8.6–10.2% (± 0.1%), respectively. The apparent activation energy (Ea), pre-exponential factor (A), and most probable kinetic function [G(α)] were calculated using thermokinetic methods as Ea = 152–164 kJ mol−1 (± 2 kJ mol−1), ln A = 27.7 ± 0.4 s−1, and G(α) = − ln(1 − α). The maximum operation temperature was estimated as 166.0 ± 0.2 °C, which was considerably lower than T0. The pyrolysis products were identified through gas chromatograph/mass and Fourier transform infrared spectrometers. As a novel finding, the main flame-retarding mechanism of [Bmim][DBP] occurred primarily in condensed phase. Complementally, [Bmim][DBP] was testified to have the flame-retardant effect on epoxy resin by limited oxygen index and vertical burning tests.