Microscale Combustion Calorimetry Research Articles

N, P co‐doped carbon quantum dot and ammonium polyphosphate as the synergistic flame retardant for epoxy resin

AbstractAn N, P co‐doped carbon quantum dot (NP‐CQD) was prepared using citric acid as the carbon source and hexachlorotripolyphosphonitrile as the nitrogen and phosphorus source. The structure and morphology of NP‐CQD were characterized. Subsequently, NP‐CQD was blended with ammonium polyphosphate (APP) to come into being a synergistic phosphorus‐nitrogen flame retardant system (SPFRS). The SPFRS was applied in epoxy resin (EP) to enhance the flame retardancy of EP. Thermal stability, flame retardancy, combustion behavior, and char residue morphology of the EP samples were determined by multiple testing methods such as thermogravimetric analysis, vertical burning (UL‐94) and limiting oxygen index (LOI) tests, microscale combustion calorimetry test, and scanning electron microscopy. When the weight ratio of NP‐CQD to APP was kept at 1:9 and 8% SPFRS was added to EP, the obtained flame‐retardant EP (EP/CQD‐APP2:18) passed the UL‐94 V‐0 level and the LOI value of EP/CQD‐APP2:18 reached 33.2%. The MCC test showed that the heat release capacity (HRC) of EP/CQD‐APP2:18 was reduced by 48.7% compared with pure EP. Morphology observation on the char residue of EP/CQD‐APP2:18 after the UL‐94 test indicated that the addition of SPFRS promoted the formation of the dense char residue layer to improve the flame retardancy of EP.Highlight An N, P co‐doped carbon quantum dot (NP‐CQD) was prepared and applied as a flame retardant. NP‐CQD and ammonium polyphosphate (APP) showed synergistic flame retardancy in epoxy resin. The proper weight ratio of NP‐CQD to APP was 1:9.

Highly transparent and flame‐retardant polyvinyl alcohol membranes crosslinked with 2‐methyl‐2,5‐dioxo‐1,2‐oxaphospholane

AbstractIn the present paper, crosslinked polyvinyl alcohol (PVA) membranes with high transparency and excellent flame retardancy were obtained by blending 2‐methyl‐2,5‐dioxo‐1,2‐oxaphospholane (OP) with a PVA water solution at the molecular scale. Fourier transform infrared spectrometry and differential scanning calorimetry were used to investigate the crosslinking reaction. The surface morphology and micromechanical assessments of the membrane were examined using nanoindentation. The limited oxygen index (LOI) and vertical flame microscale combustion calorimetry, thermogravimetric analysis, scanning electron microscopy (SEM), energy‐dispersive spectroscopy (EDS), and x‐ray photoelectron spectroscopy (XPS) were employed to evaluate the flame retardancy and reveal the corresponding mechanisms. It was found that OP reacted with PVA below 120°C. The crosslinked membranes have a rougher surface and higher hydrophilicity and lower hardness and modulus than pure PVA does. The crosslinked membranes exhibit enhanced flame retardancy and high transparency. The membrane passes the UL 94 V 0 rating with an LOI of 27.6% and achieves a transmittance of 90.2% when the OP content is 20 wt.%. The SEM, EDS, and XPS results demonstrate that the interaction between OP and PVA effectively promotes the formation of a continuous and stable char in the condensed phase.

Influence of component fractions and structure characteristic on the combustion behavior of densified wood

Densified wood (DW) is a promising structural material in high-rise timber buildings. However, fire safety issues restrict its applications. The key is to understand the influence of component fractions and dense structure on DW combustion. Here, the combustion behavior of DW is experimentally and numerically investigated. Thermogravimetric analysis (TGA) results showed that DW has 29 K earlier and 1.01 × 10−4 s−1 lower peak mass loss rate, 5 % higher residue mass than natural wood (NW) due to the component weight fraction changes by delignification. ThermaKin was applied, combined with TGA, differential scanning calorimetry and microscale combustion calorimetry, to obtain pyrolysis kinetics and thermodynamics of wood. Cone calorimeter tests showed DW has delayed ignition time because its high density enhances heat conduction and decelerates wood surface temperature increase. DW has delayed but higher value of second heat release rate peak and lower heat of combustion due to its dense structure leading to a thermally insulating and condensed char layer. Radial thermal conductivity of wood linearly increases with density. Temperature poses greater impact on thermal conductivity than density. An optimized thermal conductivity equation is proposed and applied to predict the cone calorimeter tests, yielding good agreement.

Synthesis and Characterization of a Novel DOPO-Based Flame Retardant Intermediate and Its Flame Retardancy as a Polystyrene Intrinsic Flame Retardant.

The research on intrinsic flame retardant has become a hot topic in the field of flame retardant. The synthesis of reactive flame-retardant monomer is one of the effective methods to obtain an intrinsic flame retardant. In addition, in view of the small molecular flame retardant easily migrates from the polymer during the use process, which leads to the gradual reduction of the flame retardant effect and even the gradual loss of flame retardant performance, and the advantages of atom transfer radical polymerization (ATRP) technology in polymer structure design and function customization, we first synthesized reactive flame retardant monomer 6-(hydroxymethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide (FAA-DOPO), then synthesized polystyrene bromine (PS148-Br) macromolecular initiator by ATRP technology, and finally obtained block copolymer polystyrene-b-poly{6-(hydroxymethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide} (PS-b-PFAA-DOPO) by the polymerization of FAA-DOPO initiated by macromolecular initiator PS148-Br by ATRP technology. The chemical structure of FAA-DOPO was characterized by 1D and 2D NMR (1H, 13C, DEPT 135, HSQC, COSY, NOE, and HMBC) spectra, Fourier transform infrared spectroscopy (FTIR), liquid chromatography-tandem mass spectrometry (LC-MS) and X-ray photoelectron spectroscopy (XPS). The chemical structure and molecular weight of PS-b-PFAA-DOPO were characterized by FTIR and gel permeation chromatography (GPC). The thermal and flame-retardant properties of PS-b-PFAA-DOPO were characterized by thermogravimetry analysis (TG), UL-94, limiting oxygen index (LOI), and microscale combustion calorimetry (MCC). It was found that FAA-DOPO could be used as a monomer for polymerization, although FAA-DOPO had a large steric hindrance from the chemical structure of FAA-DOPO, the UL-94 grade of PS-b-PFAA-DOPO reached the V-0 grade, and the LOI increased by 59.12% compared with PS148-Br.

Flame‐Retardant Properties and Characterization of Nylon/Tannic Acid Electrospun Fibers

Incorporating flame‐retardant compounds into polymeric composites is a key area of materials research. Halogenated flame‐retardants are most widely used; however, they are under scrutiny due to health and environmental concerns which increases interest in eco‐friendly alternatives. Tannic acid (TA) is a naturally occurring polyphenol with flame‐retardant properties. To overcome current challenges incorporating TA into polymer composites at high concentrations, nonwoven mats of nylon/TA composite nanofibers are fabricated using electrospinning. TA is incorporated at concentrations up to 50 wt% while maintaining uniform fiber morphology. Thermogravimetric analysis (TGA) shows TA within the nanofibers degrades at 230 °C and nylon degrades at 400 °C, irrespective of the initial TA concentration. Char yield increases with the concentration of TA, resulting in a maximum of 25% for fibers containing 50 wt% TA. Flame resistance is characterized using microscale combustion calorimetry (MCC) which shows composite fibers have reduced heat capacity and total heat release (THR) indicating flame resistance at ≥75 rel. wt%. Finally, ignition tests and condensed phase analysis show that TA acts as an intumescent material when embedded within the polymer matrix which produces an insulating foam‐like char under direct heat that eliminates flaming melt dripping and results in self‐extinguishing nanofibers.

Microscale combustion calorimetry assessment of green composites made with chicken feather-modified soy protein resins and jute fabric

Biodegradable, and sustainably produced, ‘green’ plastics are actively being researched to replace conventional, environmentally harmful petroleum-based plastics. However, before these green plastics get adopted, they must match the properties of their conventional counterparts. In many applications, fire-safety can be a key parameter where naturally derived green materials could potentially outcompete petroleum-based plastics. In the present research, green resins and composites were fabricated using soy protein isolate (SPI), waste chicken feather fibers (CFF), jute fabric (JF), and glutaraldehyde (GA), and evaluated for their critical fire-safety parameters through Microscale Cone Calorimetry (MCC) characterization. The loading of CFF from 0 to 30 wt% increased the specific peak heat release rate (pHRR) from 101 to 120 W/g for CFF/SPI resins without GA and from 94.5 to 114 W/g for GA crosslinked CFF/SPI resins. GA was thus shown to improve fire-safety for CFF/SPI resins. However, for JF/(CFF/SPI) composites, CFF did not show a proportional relationship with fire-safety. Rather, at 20 wt% CFF, the pHRR was minimized to 81.1 W/g for JF/(CFF/SPI) composites without GA and to 86.0 W/g for GA-crosslinked JF/(CFF/SPI) composites. This demonstrated that the addition of JF improved fire-safety despite its known combustibility, and even removed the need of the toxic crosslinker GA. Results also indicated that all variations of the fabricated CFF/SPI resins and JF/(CFF/SPI) composites had lower specific pHRR than typical petroleum-based plastics, clearly demonstrating the benefits of switching to SPI based green resins and composites. These green composites would be suitable for many applications including housing and transportation where fire-safety can be critical.

Synthesis of organic–inorganic hybrid flame retardant and its use in polyurethane composite fiber membrane

AbstractIn this article, we presented an inventive organic–inorganic hybrid flame retardant, MPKG, by the strategic reaction of phytic acid (PA) with melamine (MA), γ‐aminopropyl triethoxysilane (KH550) and graphene oxide (GO). Subsequently, an MPKG/PU fiber membrane was fabricated through electrospinning, wherein MPKG was seamlessly incorporated into the PU spinning solution. The morphology and chemical structures of the flame retardants were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and x‐ray photoelectron spectroscopy (XPS). The flame retardancy and resilience to soaping of the fiber membranes were assessed via the limiting oxygen index (LOI), thermogravimetric analysis (TGA), and microscale combustion calorimetry (MCC). Impressively, the results demonstrate a significant 38.8% reduction in total heat release (THR) for the MPKG/PU fiber membrane in comparison to pure PU fiber membrane. Moreover, the incorporation of MPKG leads to an increase in LOI from 18.8% to 21.5% for the PU fiber membrane, accompanied by a notable enhancement in char yield at 800°C from 13.5% to 28.5%. These results underscore the augmentative impact of MPKG on the flame retardancy of PU fiber membrane. Remarkably, the MPKG/PU fiber membrane exhibits robust soaping resistance, with the LOI maintaining a level above 20% post‐soaping.

Multifunctional deoxybenzoins: Preparation of low heat release polymer networks by orthogonal crosslinking

Multifunctional epoxide monomers present opportunities to design cross-linked networks with conveniently tunable thermal and mechanical properties. This paper describes the synthesis of a novel, multifunctional deoxybenzoin monomer containing both epoxide and allyl groups, and its use in the preparation of epoxide networks. The orthogonal reactivity of these functional groups, operating via epoxide-amine and thiol-ene chemistry, facilitated the formation of networks with tunable glass transition temperatures and crosslink densities. Thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC) characterization revealed these networks to possess impressively low heat release properties (∼50% lower than conventional bisphenol A (BPA)-based networks) and very high char residues that reached ∼60%. Overall, introducing functional deoxybenzoin epoxide monomers into these types of network architectures imparts a method for combining low heat release structures with the advantageously tunable physical and mechanical properties of polymer networks.

Flammability and burning behaviour of fire protected timber

Decarbonization has driven the construction industry to rediscover biobased, but inherently combustible, materials like timber. To avoid compromising fire safety, reaction to fire of timber can be effectively reduced by fire retardant surface coatings or impregnation treatments. Using a combination of simultaneous thermal analysis, microscale combustion calorimetry and cone calorimetry, vacuum-pressure impregnated (boron free, phosphorus-based) plywood was tested against plywood coated with a thin layer of water-based fire retardant intumescent coating (melamine free, phosphorus-based). Comparing the peak heat release rate (pHRR) and total heat release (THR) of the three plywood samples, the impregnated was lowest, and the coated was lower (pHRR −34% and −20%, THR -45% and −21% respectively) relative to the untreated plywood. In contrast, the coating layer postponed sustained flaming for longer than impregnated wood and delayed burnthrough, effects critical to the growth rate of a developing fire. Better understanding of the assessment of flammability of fire protected timber has been obtained using cone calorimeter data supported by microscale analyses. The results challenge the simple flammability ranking based on total heat release, and highlight the need for further development of a methodology for comparing different fire protection strategies for timber.

Plasticized polyvinyl chloride/melamine‐cyanurate modified Mg(OH)2@bentonite nanocomposites; mechanical, thermal, and flame retardant properties

AbstractIn this work, a strategy was used to combine Mg(OH)2 nanoparticles (MDH), the bentonite nano‐sheets, and melamine cyanurate (MC) to prepare dioctyl phthalate (DOP) plasticized polyvinyl chloride (PVC) nanocomposites with increased thermal stability, Limiting Oxygen Index (LOI), and tensile strength as well as reduced total heat release. To prepare MC‐modified Mg(OH)2@bentonite nanohybrid (MMHB), MDH was installed on the calcined bentonite and consequently modified with MC. The nanocomposite thin films were prepared from plasticized‐PVC and MMHB using the solvent casting method. It was found that the combination of MDH and the bentonite nano‐sheets in the presence of MC could improve the PVC properties. Thermogravimetric analysis (TGA) in both N2 and air atmospheres, indicated that the thermal stability of PVC was enhanced via adding MMHB, which was evident by the increased thermal decomposition temperature. The microscale combustion calorimetry (MCC) results of the PVC nanocomposites with 5% and 8% by mass of MMHB revealed that an optimal isolating layer is formed, which increased flame retardant properties. The PVC matrix nanocomposite containing 8% by mass of MMHB with LOI value of 33.4% exhibited high flame retardancy. Moreover, the tensile strength and elastic modulus of the sample containing 5% by mass of MMHB increased by 65.5% and 55.2% compared to those of pristine PVC, respectively.Highlights A nanohybrid was prepared from Mg(OH)2 (MDH) and calcined bentonite. Preparation of melamine cyanurate (MC). Preparation of MC‐modified MDH@bentonite nanohybrid (MMHB). Effects of MMHB on thermal stability and flame retardancy of plasticized PVC. The efficient flame retardancy effect of the additive on plasticized PVC.

The Components' Roles in Thermal Stability and Flammability of Cork Powder.

In this study, an analysis of the influence of extractives, suberin and lignocellulosic components on the pyrolysis decomposition and fire reaction mechanisms of a cork oak powder from Quercus suber L. is presented. The summative chemical composition of cork powder was determined. Suberin was the main component at 40% of the total weight, followed by 24% of lignin, 19% of polysaccharides and 14% of extractives. The absorbance peaks of cork and its individual components were further analyzed by means of ATR-FTIR spectrometry. Thermogravimetric analysis (TGA) showed that the removal of extractives from cork slightly increased the thermal stability between 200 °C and 300 °C and led to the formation of a more thermally stable residue at the end of the cork decomposition. Moreover, by removing suberin, a shift of the onset decomposition temperature to a lower temperature was noticed, indicating that suberin plays a major role in enhancing the thermal stability of cork. Furthermore, non-polar extractives showed the highest flammability with a peak of heat release rate (pHRR) of 365 W/g analyzed by means of micro-scale combustion calorimetry (MCC). Above 300 °C, the heat release rate (HRR) of suberin was lower than that of polysaccharides or lignin. However, below that temperature it released more flammable gases with a pHRR of 180 W/g, without significant charring ability, contrary to the mentioned components that showed lower HRR due to their prominent condensed mode of action that slowed down the mass and heat transfer processes during the combustion process.

Enhanced safety of polymer solid electrolytes by using black phosphorene as a flame-retardant

Solid polymer electrolytes attract much attention due to their good flexibility and good interfacial contact property. However, the inherent thermal instability of polymers inhibits the practical application of solid polymer electrolytes. In this work, the black phosphorene nanosheet, a fire-retardant additive, was introduced and incorporated into poly (ethylene oxide) (PEO)-based solid polymer electrolyte to improve the thermal property. The BP/PEO based solid polymer electrolyte membrane is thermally stable, nonflammable, and mechanically strong, more than 400 h of cycling with low polarization based on a Li-Li symmetric cell was achieved. LiFePO4//Li solid state battery with the BP/PEO based solid polymer electrolyte shows a high-capacity performance (153 mAh g−1 at 0.1 C) as well as cycling performance (100 cycles at 0.2 C rate) at 60 °C. The flammability tests indicated that a small amount of black phosphorene can make the electrolyte display good non-flammability. In the micro-scale combustion calorimetry test, the peak heat release rate of BP/PEO based solid polymer electrolyte reduced by 62.5% and flame ignition time is slower compared with the PEO based solid polymer electrolyte without incorporating black phosphorene. The present work demonstrated that the black phosphorene nanosheets do not weaken the electrochemical properties of solid polymer electrolytes, but also enhance their thermal properties.

Pyrolysis and thermal degradation studies of non-isocyanate polyurethanes modified by polyhedral oligomeric silsesquioxanes

This work reports on the thermal properties of non-isocyanate polyurethanes (NIPUs) obtained via the polyaddition reaction of polyether diamine with five membered tri(cyclic carbonate) by using a prepolymerization method. The non-isocyanate polyurethanes were further chemically modified by trifunctional polyhedral oligomeric silsesquioxane (POSS) - triglycidylisobutyl POSS (3epPOSS), resulting in hybrid composite materials containing 5 to 15 wt% POSS. Thermal properties of the obtained materials were studied by various methods, such as Thermogravimetric analysis (TGA), Pyrolysis with gas chromatography and mass spectrometry (Py-GC/MS), and Microscale Combustion Calorimetry (MCC), and were later discussed in dependence of their composition and structure assessed by Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) techniques. FTIR spectra confirm the successful synthesis of NIPUs and their hybrids with POSS. The results of XRD and SEM revealed homogeneous distribution of silsesquioxane in the bulk of the NIPU matrix. Depending on the POSS concentration in the PU hybrids, various self-assembling structures were formed. TGA analysis indicated a two- and three-step degradation process of NIPU materials in inert and oxidative atmospheres, respectively. Significantly higher degradation temperatures and a remarkably reduced degradation rate for composite materials compared to unmodified NIPU matrix were observed during the second degradation step under an oxidative atmosphere. Based on the overall stabilization effect (OSE), hybrids containing 10 and 15 wt% of 3epPOSS were more thermally stable than the unmodified NIPU matrix. Py-GC/MS demonstrated that the products of NIPU thermal decomposition originate from hydroxyurethane moieties, main substrate core structures, and others, such as catalysts. Incorporation of 3epPOSS into the NIPU matrix decreases its flammability, as evidenced by the results of the MCC, with a nearly 20 % reduction effect noted for the composite with of 15 wt% of POSS, compared to the unmodified NIPU matrix. Importantly, chemical modification of NIPU by POSS caused a reduction of the heat of combustion in the final stage of degradation by ca. 30 %.

Thermal decomposition of vegetative fuels and the impact of measured variations on simulations of wildfire spread

This manuscript presents new measurement data from milligram-scale thermal decomposition experiments – thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC) – conducted on stems and leaves (i.e., needles) of six plant species commonly found across the United States. For each fuel, measurement data from TGA experiments was analyzed to determine effective thermal decomposition mechanisms and the associated kinetics of their constituent reactions. Results of this model calibration were compared to standard (i.e., ‘generalized’) approaches to obtain kinetic parameters available in the literature. MCC experiments were repeated under identical experimental conditions to determine the heats of complete combustion of all gaseous volatiles produced by these vegetative fuels and to validate the decomposition mechanisms and species char yields determined from TGA data. Through a coupled analysis of TGA and MCC measurement data, an estimate of the heats of combustion of the gaseous volatiles produced by individual reaction steps in the fuel’s decomposition was also made. Between different fuels, distinct differences were measured in the onset temperature of decomposition, the temperature range of decomposition, the number of apparent reactions, and the peak measured mass loss and heat release rates (as well as the temperatures at which they occur). To analyze the impact of these variations on predictions of wildfire behavior, a modeling study was then conducted in which simulations of wildland fire experiments were repeated using the thermal decomposition mechanisms and heats of combustion determined for each of the fuel species tested in this work. Model-predicted fire spread rate in these simulations varied between 0.34 m s−1 and 0.80 m s−1 demonstrating a notable dependence (up to a factor of 2x) on measured variations in thermal decomposition mechanism and a second-order dependence on the use of either reaction-step-specific or single (global) heats of combustion.

Flame resistant cotton lines generated by synergistic epistasis in a MAGIC population.

Textiles made from cotton fibers are flammable and thus often include flame retardant additives for consumer safety. Transgressive segregation in multi-parent populations facilitates new combinations of alleles of genes and can result in traits that are superior to those of any of the parents. A screen of 257 recombinant inbred lines from a multi-parent advanced generation intercross (MAGIC) population for naturally enhance flame retardance (FR) was conducted. All eleven parents, like all conventional white fiber cotton cultivars produce flammable fabric. MAGIC recombinant inbred lines (RILs) that produced fibers with significantly lower heat release capacities (HRC) as measured by microscale combustion calorimetry (MCC) were identified and the stability of the phenotypes of the outliers were confirmed when the RILs were grown at an additional location. Of the textiles fabricated from the five superior RILs, four exhibited the novel characteristic of inherent flame resistance. When exposed to open flame by standard 45° incline flammability testing, these four fabrics self-extinguished. To determine the genetic architecture of this novel trait, linkage, epistatic and multi-locus genome wide association studies (GWAS) were conducted with 473k SNPs identified by whole genome sequencing (WGS). Transcriptomes of developing fiber cells from select RILs were sequenced (RNAseq). Together, these data provide insight into the genetic mechanism of the unexpected emergence of flame-resistant cotton by transgressive segregation in a breeding program. The incorporation of this trait into global cotton germplasm by breeding has the potential to greatly reduce the costs and impacts of flame-retardant chemicals.

Synthesis and thermal properties of novel bismaleimides containing cardo and oxazine structures and the thermal transition behaviors of their polymer structures

In this work, three bismaleimides containing cardo and ortho-oxazine structures, with dual advantages of bismaleimide and benzoxazine resin, were synthesized. Their chemical structures were characterized by Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The kinetics of curing and kinetic model were investigated by non-isothermal differential scanning calorimetry. The curing reaction of the bismaleimide was studied by in-situ FT-IR spectroscopy. Studies showed that both bismaleimide and benzoxazine provided the new structure with better thermal stability and solubility, compared to similar type of materials and commercial bismaleimides. Additionally, the further thermal rearrangement of the internal structure of the polymer at high temperature formed a benzoxazole structure with higher thermal stability. The rearrangement due to thermal changes was confirmed by in-situ FT-IR and solid-state 13C-NMR spectroscopy. Microscale combustion calorimetry (MCC) showed that both, bismaleimide and benzoxazole resins, were formed after thermal rearrangement and had excellent flame-retardant properties.

Preparation of DOPO‐derived magnesium phosphate whisker and its synergistic effect with ammonium polyphosphate on the flame retardancy and mechanical property of epoxy resin

AbstractIn this study, a magnesium phosphate whisker (DPM‐H) was synthesized by the acid–base neutralization reaction between magnesium hydroxide and 10‐hydroxy‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐OH) at 120°C. A new synergistic intumescent flame retardant (IFR) for epoxy resin (EP), which was composed of DPM‐H and ammonium polyphosphate (APP) was thoroughly studied. When the IFR loading was 8%, with the DPM‐H to APP weight ratio at 1:7, the prepared flame‐retardant EP (EPDA‐2) passed the vertical burning tests (UL‐94) V‐0 rating and obtained the limiting oxygen index (LOI) value of 29.3%. Microscale combustion calorimetry (MCC) results showed that the total heat release (THR) of EPDA‐2 reduced by 32.1% compared with pure EP. Meanwhile, the addition of DPM‐H can partially solve the problem of the decrease of the EP mechanical property caused by the addition of APP. Compared with the flame‐retardant EP with the 8% loading of APP, the impact strength of EPDA‐2 increased 152.3%.

Thermal Properties and Flammability Characteristics of a Series of DGEBA-Based Thermosets Loaded with a Novel Bisphenol Containing DOPO and Phenylphosphonate Units.

Despite a recent sustained preoccupation for developing biobased epoxies with enhanced applicability, such products have not been widely accepted for industry because of their inferior characteristics compared to classic petroleum-based epoxy thermosets. Therefore, significant effort is being made to improve the flame retardance of the most commonly used epoxies, such as diglycidyl ether-based bisphenol A (DGEBA), bisphenol F (DGEBF), novalac epoxy, and others, while continuously avoiding the use of hazardous halogen-containing flame retardants. Herein, a phosphorus-containing bisphenol, bis(4-(((4-hydroxyphenyl)amino)(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)methyl)phenyl) phenylphosphonate (BPH), was synthesized by reacting bis(4-formylphenyl)phenylphosphonate with 4-hydroxybenzaldehyde followed by the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to the resulting azomethine groups. Environmentally friendly epoxy-based polymer thermosets were prepared by using epoxy resin as polymer matrix and a mixture of BPH and 4,4'-diaminodiphenylsulfone (DDS) as hardeners. A hyperbranched phthalocyanine polymer (HPc) and BaTiO3 nanoparticles were incorporated into epoxy resin to improve the characteristics of the final products. The structure and morphology of epoxy thermosets were evaluated by infrared spectroscopy and scanning electron microscopy (SEM), while the flammability characteristics were evaluated by microscale combustion calorimetry. Thermal properties were determined by thermogravimetric analysis and differential scanning calorimetry. The surface morphology of the char residues obtained by pyrolysis was studied by SEM analysis.

Microscale Combustion Calorimetry as a New Method of Composition and Heating Value Determination of Miscanthus - An Early View

Microscale Combustion Calorimetry as a New Method of Composition and Heating Value Determination of Miscanthus - An Early View

Fully Coupled Three-Dimensional Simulation of Downward Flame Spread over Combustible Material.

Three-dimensional simulations of laminar flame propagating downwards the vertical surface of a rigid polyurethane slab heated by a radiative panel are presented and compared with the measurement data. The gas-phase model (ANSYS Fluent) allows for finite-rate volatile oxidation, soot formation and oxidation, emission, transfer, and absorption of thermal radiation. The solid-phase model Pyropolis considers heat transfer across the material layer and generation of combustible volatiles in thermal decomposition of the material. Kinetic model of material decomposition is derived to obey the microscale combustion calorimetry data for different heating rates. Transient behavior of propagating flame and pyrolysis zone, as well as spatial distributions of heat flux components, temperature, and mass burning rates over the specimen surface are examined. Variation of the thermal properties of the material during its thermal decomposition, as well as the specimen surface emissivity and reradiation are shown to be the important issues strongly affecting model predictions. Two distinct modes of counterflow flame spread, thermal and kinetic, are identified. In the thermal mode corresponding to fast chemistry in the gaseous flame, the flame propagation velocity is governed by the heating rate of the combustible material ahead of the flame front. Alternatively, in the kinetic mode, it is limited by the burning velocity of the volatile-air mixture forming ahead of the flame front. Simulation results are favorably compared with the measured propagation velocity.