Microscale Combustion Calorimetry Research Articles

Fabrication of transparent clay-polymer hybrid coatings on PET film to enhance flame retardancy and oxygen barrier properties

A multifunctional nanocoating, consisting of montmorillonite (MMT) / laponite (LAP) / polyvinyl alcohol (PVA), was deposited onto the surface of polyethylene terephthalate (PET) film via a facile co-assembly process. As a result, the PVA/LAP/MMT coating endowed PET film with improved flame retardancy and oxygen barrier. At 4 layers deposition of PVA/LAP/MMT, the film maintained more than 90% transmittance to the visible light. The microscale combustion calorimetry revealed, compared with control PET sample, the peak of heat release rate and total heat release of PET@(MMT/LAP/PVA)4 sample were reduced by 67.4% and 45.3%, respectively. The oxygen transmission rate significantly reduced at the same time. The reason was speculated at the combination of MMT and LAP, a more compact shielding layer was formed on the PET substrate.

Phosphorus‐containing polyamide Mg(OH)2 nanocomposite coating on surface of poly(vinyl chloride) thin film: Study on thermal stability, flammability, and mechanical properties

Surface of poly(vinyl chloride) (PVC) thin films was coated using DOPO‐based polyamide (DBPA) coating and DBPA/Mg(OH)2 nanocomposites (DBPN) coating by dip‐coating process. For this purpose, a new DOPO‐based dicarboxylic acid (DBDA) was synthesized and used for preparation of DBPA and organically surface modification of Mg(OH)2 nanoparticles. The effects of DBPA and DBPN coatings on the morphology, thermal stability, combustion, and mechanical properties of PVC were investigated. The uniform dispersion of Mg(OH)2 nanoparticles (nano‐MDH) and organically coating manner on the surface of the PVC films were confirmed by ATR‐IR spectroscopy, X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray, and elemental mapping. From thermal gravimetry analysis (TGA) results, the 10 mass% loss temperature (T10) increased from 268°C to 272°C in PVC coated with DBPA‐containing 10 mass% of modified Mg(OH)2 (MMH). Also the char residue, first and second mass loss temperatures of all PVC coated were increased compared with the neat PVC film. According to microscale combustion calorimetry (MCC) results, the peak of heat release rate (pHHR) and total heat release (THR) were decreased from 128 ± 2 to 69 W/g and 12 ± 1 to 4 ± 2 KJ/g for PVC film coated with DBPA‐containing 10 mass% of MMH, compared with the neat PVC. From tensile test results, tensile strength was increased from 31.78 ± 0.8 to 39.64 ± 0.9 MPa for PVC coated with polyamide‐containing 5 mass% of MMH compared with the neat PVC.

A Flame-Retardant Phytic-Acid-Based LbL-Coating for Cotton Using Polyvinylamine.

Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with the highest density of amine groups of all polymers. Vertical flame tests revealed a flame-retardant behavior with no afterflame and afterglow time for a coating of 15 bilayers (BL) containing 2% phosphorus and 1.4% nitrogen. The coating achieved a molar P:N ratio of 3:5. Microscale combustion calorimetry (MCC) analyses affirmed the flame test findings by a decrease in peak heat release rate (pkHRR) by more than 60% relative to unfinished CO. Thermogravimetric analyses (TGA) and MCC measurements exhibited a shifted CO peak to lower temperatures indicating proceeding reactions to form an isolating char on the surface. Fourier transform infrared spectroscopy (FTIR) coupled online with a TGA system, allowed the identification of a decreased amount of acrolein, methanol, carbon monoxide and formaldehyde during sample pyrolysis and a higher amount of released water. Thereby the toxicity of released volatiles was reduced. Our results prove that PA enables a different reaction by catalyzing cellulosic dehydration, which results in the formation of a protective char on the surface of the burned fabric.

Boosting phosphorus–nitrogen–silicon synergism through introducing graphene nanobrick wall structure for fabricating multifunctional cotton fabric by spray assisted layer-by-layer assembly

Efficient construction of quaternary composite coating on cotton fabric was presented by spraying aqueous solutions of graphene oxide, 3-aminopropyl triethoxysilane, sodium alginate and ammonium polyphosphate for providing the flame retardant, antimicrobial and antistatic properties. The thermal degradation of cotton was monitored by thermogravimetric analysis and the result showed the introduction of graphene oxide (GO) as a nanobrick wall structure can greatly boost the phosphorus–nitrogen–silicon synergism. The flame retardance performance was evaluated by vertical burning test and microscale combustion calorimetry, which indicated that the assembly coating eliminated the afterglow during combustion and decreased the pHRR value. Particularly, (GO1)10 cotton fabric has a significant self-extinguished effect with a pHRR value of about 3.2% of uncoated cotton, and moreover, can effectively inhibit the growth of E. coli and S. aureus. Furthermore, it also keeps highly reliable flame retardant and antistatic ability during the washing test. This simple and green approach provides new insights into the fabrication of cotton fabrics with multifunction including flame-retardant, antimicrobial and antistatic properties in a large scale.

A phosphorus- and nitrogen-containing DOPO derivative as flame retardant for polylactic acid (PLA)

The preparation of high-efficient flame-retardant PLA remains a major challenge due to the unavoidable loss in mechanical properties. In this study, a DOPO derivative containing phosphorus and nitrogen in the molecular structure with amino as terminal group (DOPO-NH2) was incorporated into PLA to improve the flame resistance. The addition of this DOPO derivative on the thermal stability, flame retardancy and mechanical properties of PLA was investigated. With loading of only 5 mass% DOPO-NH2, the LOI value increased to 26% and UL-94 V-0 was attained. The heat release rate showed obvious decrease by microscale combustion calorimetry. Moreover, the mechanical properties of PLA/5DOPONH2 composite have not deteriorated significantly due to the low loading and the existence of hydrogen bond between DOPO-NH2 and PLA matrix.

Assessment of lignin as a carbon source in intumescent coatings containing polyaniline

Lignin, a vegetable compound, is the second most abundant biorenewable and biodegradable polymer in nature. In this study, the addition of this compound to paints containing ammonium polyphosphate (APP) and expandable graphite as pigments was investigated to improve the fire protection performance of intumescent coatings. The combination of lignin with polyaniline (PANI) in the formulations was also evaluated, as previous studies have shown that PANI-based paints show promising results in intumescent coatings. For this purpose, the thermal protection of mild steel samples coated with these organic coatings was evaluated during a fire resistance test, with the sample exposed to a Bunsen torch. During the test, temperature data and thermography images for the steel surface were collected. The coatings were also evaluated by thermogravimetric analysis and microscale combustion calorimetry. It was found that all coatings formulated provided good fire protection to the steel substrate and the lignin could be a good option to replace nonrenewable sources in intumescent paints, since the sample coated with the paint containing 10 wt% lignin reached 230°C after 30 min of assay. In addition, when this compound was used in combination with PANI, the flame protection was even better. The best performance was observed for the paint formulated with combination of 10 wt% lignin and 10 wt% PANI-ES, whose metal substrate temperature was 170°C after 30 min of assay.

Determination of pyrolysis and combustion properties of poly(vinylidene fluoride) using comprehensive modeling: Relating heat transfer to the intumescent char's porous structure

A systematic methodology, utilizing improved experimental and numerical techniques, is used to analyze the heat transfer within an intumescent char. Thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimetry were conducted on 4–7 mg samples to determine the kinetics and thermodynamics of thermal decomposition and heats of complete combustion of gaseous pyrolyzates. Subsequently, 0.07 m diameter disk-shaped samples were pyrolyzed in the Controlled Atmosphere Pyrolysis Apparatus II to characterize the thermal transport within the decomposing solid and evolving char layer. ThermaKin2Ds was employed to analyze all the experimental data, using inverse analysis techniques, and to perform predictions. Poly(vinylidene fluoride), a widely used intumescent polymer, was investigated in this study. The model parameterization process revealed notable instabilities in the sample surface emissivity during pyrolysis. However, the resulting model can predict the experimental gasification mass loss rate with a mean error of 29%. Additionally, the physical structure of the porous char was analyzed to enable the formulation of quantitative relationships between relevant thermal transport parameters and the intumescent char's structure. A prominent linear correlation was revealed during this exercise: the product of density and thermal conductivity was directly proportional to an increasing char porosity derived from image analysis.

Fully bio-based fire-safety viscose/alginate blended nonwoven fabrics: thermal degradation behavior, flammability, and smoke suppression

Ecofriendly bio-based alginate fibres are one of the inherently flame-retardant fibres. Can the incorporation of alginate fibres to viscose fibres enhance the flame retardancy and decrease the smoke release of prepared viscose/alginate blended nonwoven fabrics? Aiming to resolve this question, in the present work, viscose/alginate blended nonwoven fabrics were prepared in a green way without any pollution. Vertical flame test, cone calorimetry test and microscale combustion calorimetry results indicated that the incorporation of alginate fibres enhanced the flame retardancy and fire behaviors; what is more, the incorporation of alginate fibres seriously prolonged time to ignition. The results mentioned above indicate that alginate fibres can enhance the flame retardancy and inhibit the smoke release of viscose fibres. The incorporation of alginate fibres altered the thermal stability of viscose fibres and decreased the flammable gas emissions, thus improving the flame retardancy of viscose/alginate blended nonwoven fabrics. A conclusion can be made that inherently bio-based alginate fibres can be used as a kind of flame retardant to flame-retard viscose fibres. The incorporation of alginate fibres improves the flame retardancy and suppresses the release of smoke for viscose/alginate blended nonwoven fabrics.

Biobased high-performance tri-furan functional bis-benzoxazine resin derived from renewable guaiacol, furfural and furfurylamine

A novel fully biobased tri-furan functional bis-benzoxazine resin has been synthesized using guaiacol, furfural, furfurylamine and paraformaldehyde as raw materials via a two-step reaction approach. The detailed chemical structure of this newly obtained bis-benzoxazine monomer has been identified by NMR and FT-IR spectroscopies and elemental analysis. In addition, another bio-based benzoxazine monomer has also been synthesized based on the Mannich condensation of guaiacol, furfurylamine and paraformaldehyde for comparison. The polymerization behaviors of benzoxazines are investigated by DSC and in situ FT-IR, and the thermal and fire-related performances of resulting thermosets are investigated by TGA and micro-scale combustion calorimetry (MCC), respectively. Notably, the corresponding polybenzoxazine derived from the newly developed tri-furan functional bis-benzoxazine shows very excellent thermal stability with a Tg of 290 °C and a Td10 (the temperature at a weight loss of 10%) of 375 °C in nitrogen atmosphere. Moreover, a non-ignitable polybenzoxazine has also been achieved as shown by the very low heat release capacity (30.4 J g−1 K−1) and total heat release value (5.8 kJ/g), making this bio-based thermosetting resin a promising material for high-performance applications.

Silica–Phenolic Nanocomposite Ablatives for Thermal Protection Application

A novel class of ablative materials using phenolic resin, silica fabric, and nano-zirconium dioxide is being developed as a potential alternative for use in high-heat-flux thermal protection applications. Four new silica–phenolic ablatives have been fabricated using tandem nanocomposite formulations. Each of the tandem composites consist of nano-zirconium dioxide with small amounts of one of the following additives: multiwalled carbon nanotubes, nano-graphene platelets, alumina nanofibers, and nano-boron carbide. Materials have been fabricated, characterized, and compared using thermal and microanalysis. Thermogravimetric analysis and microscale combustion calorimetry were used to compare char yield, thermal stability, and flammability properties. Oxy-acetylene test bed aerothermal ablation testing was used to evaluate the composites under a high heat flux of environment. Data analysis on recession rate, mass loss rate, backside heat-soaked temperature, surface temperature, and materials surface behavior were collected and used as a comparison tool to rank ablation performance of candidate materials. After testing of the candidates, it was determined that the nanocomposite containing nano-boron carbide in tandem with nano-zirconium dioxide was the best-performing candidate, demonstrating superior ablation properties, such as mass loss, recession rate, and insulative properties.

Intumescent, Epoxy-Based Flame-Retardant Coatings Based on Poly(acrylic acid) Compositions

Intumescent coatings expand upon exposure to a flame to create a protective char layer between the flame and underlying substrate. Widely used commercially, these coatings are applied notably to steel load-bearing beams, significantly extending their time to failure. Boric acid has proved to be a particularly effective additive in the formulation in these coatings, although regulatory concerns are driving an urgent need for more environmentally friendly additives. We report here the characterization of poly(acrylic acid) (PAA) for its use as a novel material in flame retardant and intumescent coatings. Thermogravimetric analysis (TGA) and microscale combustion calorimetry (MCC) were performed on the novel flame retardant additives to evaluate individual degradation mechanisms and heat release rates. Promising compositions were immobilized in an epoxy binder and formulated with other intumescent additives such as ammonium polyphosphate (APP) and melamine (MEL) to evaluate performance in a coating system. These formulations were then evaluated via quantitative cone calorimetry. Particular PAA-containing formulations show peak heat release rates (PHRR) and total heat release (THR) of 283 kW/m2 and 50.5 MJ/m2, respectively, which compare favorably to data for BA-containing systems, specifically PHRR = 229 kW/m2 and THR = 43.1 MJ/m2. Results showed promise and need for further investigation in to PAA as a multi-functional additive for use in flame retardant and intumescent coatings.

Unusual role of labile phenolics in imparting flame resistance to polyamide

In the quest for development of halogen-free FR additive and better understanding of the structure-flammability relationship, here we report the synthesis and characterization of a series of phenolic and benzylic succinamides, with and without aliphatic hydroxyl groups. These compounds allow for detailed investigation of the influence of these functional groups on thermal stability and FR properties in their native form and as coatings on Nylon 66 fabric. The thermal stability, char formation, heat release characteristics and thermal decomposition pathway of synthesized succinamides were studied by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC) and TGA-FTIR (Fourier Transform Infrared Spectroscopy). Phenolic succinamide, 2,3 dihydroxy-N1,N4-bis(4-hydroxybenzyl)succinamide (C1) and N1,N4-bis(4-hydroxybenzyl)succinamide (C3), exhibits about 20% char yield with low heat release characteristics while benzylic succinamides, N1,N4-dibenzyl-2,3-dihydroxysuccinamide (C2) and N1,N4-dibenzylsuccinamide (C4), exhibit poor char yield and high heat release characteristics. Thermal decomposition followed by evolved gas analysis of all these succinamides indicate that the decomposition pathway is very much dependent on the presence of phenolic moieties. Heat release characteristic and flammability of Nylon 66 coated with succinamides (10% by weight) clearly indicate that the coating of C1 and C3 impart flame resistance to Nylon 66. These studies clearly reveal that phenolic derivatives are essential for improving the thermal stability, flame resistance and lowering the heat release characteristics of Nylon 66 through char formation.

Evaluation of additively manufactured ultraperformance polymers to use as thermal protection systems for spacecraft

AbstractIn this study, high‐temperature thermoplastic polymers were three‐dimensional (3D) printed and evaluated for ablation performances for the first time. The purpose of this study is to fabricate, test, and evaluate several ultraperformance thermoplastics, including polyetherimide (PEI), polyether ether ketone (PEEK), and poly(ether ketone ketone) (PEKK) for thermal, flammability, and ablation properties using fused filament fabrication. Among all tested materials, PEKK exhibit the highest char yield while the two PEEKs exhibit the highest decomposition temperature. Although PEI have the lowest onset decomposition temperature, microscale combustion calorimetry results indicate that it has the lowest heat release properties. For the 15 s oxyacetylene test bed (OTB) ablation test, all five materials experienced various amount of intumescent or swelling behavior. Samples after 30 s test experienced greater mass loss among which PEKK and ULTEM 9085 shows the highest char yield. Scanning electron microscopy microstructural analysis of the char and pyrolysis zones reveal highly porous char structures caused by the rapid generation of the volatile decomposition products. To fully exploit the experimental data provided by the OTB, the flowfield generated during aerothermal testing using this heat source was modeled. Computational fluid dynamics analysis using Ansys/Fluent 19.1 code was used to the heat transfer between the ablative surface and the combustion gases generated by the OTB and compared with experimental results.

Fabrication of fullerene decorated by iron compound and its effect on the thermal stability and flammability for high‐density polyethylene

SummaryFullerene decorated by iron compound (C60‐Fe) is fabricated via solution reaction and characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), wide‐angle X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Upon incorporating C60‐Fe into high‐density polyethylene (HDPE) matrix by melt blending, the thermal and thermo‐oxidative stability of HDPE are considerably increased, the oxidative induction time (OIT) is dramatically extend. When the concentration of C60‐Fe reached 5 wt%, the onset degradation temperature in air increased from 352°C to 422°C, and the OIT dramatically delayed from 4.5 to 47.8 minutes. Moreover, from microscale combustion calorimetry (MCC), C60‐Fe can reduce the peak heat release rate (PHRR), heat release capacity (HRC), and total heat release (THR) values of the composites, all of which are very important parameters for evaluating the fire retardancy of a polymeric material.

Enhanced thermal properties of poly(lactic acid)/MoS2/carbon nanotubes composites

In this work, few-layered molybdenum disulfide (MoS2) was functionalized with metal oxide (MxOy) nanoparticles which served as a catalyst for carbon nanotubes (CNT) growth in the chemical vapour deposition (CVD) process. The resulting MoS2/MxOy/CNT functionalized nanomaterials were used for flame retarding application in poly(lactic acid) (PLA). The composites were extruded with a twin-screw extruder with different wt% loading of the nanomaterial. Full morphology characterization was performed, as well as detailed analysis of fire performance of the obtained composites in relation to pristine PLA and PLA containing an addition of the composites. The samples containing the addition of MoS2/MxOy/CNT displayed up to over 90% decrease in carbon oxide (CO) emission during pyrolysis in respect to pristine PLA. Microscale combustion calorimetry testing revealed reduction of key parameters in comparison to pristine PLA. Laser flash analysis revealed an increase in thermal conductivity of composite samples reaching up to 65% over pristine PLA. These results prove that few-layered 2D nanomaterials such as MoS2 functionalized with CNT can be effectively used as flame retardance of PLA.

Novel Approaches to Modelling Flammability Characteristics of Polymethyl Methacrylate (PMMA) via Multivariate Adaptive Regression Splines and Random Forest Methods

Soft-computing techniques for fire safety parameter predictions in flammability studies are essential for describing a material fire behaviour. This study proposed, two novel Artificial Intelligence developed models, Multivariate Adaptive Regression Splines (MARS) and Random Forest (RF) methods, to model and predict peak heat release rate (pHRR) of Polymethyl methacrylate (PMMA) from Microscale Combustion Calorimetry (MCC) experiment. From the statistical analysis, MARS presented the highest coefficient of determination (R2) values of (0.9998) and (0.9996) for training and testing respectively, with low MAD, MAPE and RMSE values. Comparatively, MARS outperformed RF in the predictions of pHRR, through its model algorithms that generated optimized equations for pHRR predictions, covering all non-linearity points of the experimental data. Amongst the input variables (sample mass, THR, HRC, pTemp and pTime), heating rate (β), highly influenced pHRR outcome predictions from MARS and RF models. However, to validate the performance and applicability of the proposed models. Results of MARS and RF were benchmarked with that from Artificial Neural Network (ANN) methods. The MARS and RF models observed the least error deviation when compared with pHRR results for PMMA from the ANN models. This study therefore, recommends the adoption of MARS and RF in the predictions of flammability characteristics of polymeric materials.

Application of Adaptive Neuro-Fuzzy Inference System in Flammability Parameter Prediction.

The fire behavior of materials is usually modeled on the basis of fire physics and material composition. However, significant strides have been made recently in applying soft computing methods such as artificial intelligence in flammability studies. In this paper, multiple linear regression (MLR) was employed to test the degree of non-linearities in flammability parameter modeling by assessing the linear relationship between sample mass, heating rate, heat release capacity (HRC) and total heat release (THR). Adaptive neuro-fuzzy inference system (ANFIS) was then adopted to predict the HRC and THR of the extruded polystyrene measured from microscale combustion calorimetry experiments. The ANFIS models presented excellent predictions, showing very low mean training and testing errors as well as reasonable agreements between experimental and predicted datasets. Hence, it can be inferred that ANFIS can handle the non-linearities in flammability modeling, making it apt as a modeling technique for accurate and effective flammability assessments.

Effect of Perlite on Fire Protection of Waterborne Coatings for Steel Structure

In this paper, perlite was used as a kind of modifier to prepare waterborne fire resistive coatings for steel structure. The influence of perlite on the properties of the fire resistive coatings was investigated with the help of thermogravimetric analysis (TGA), micro-scale combustion calorimetry (MCC) and fire protection test. The TGA results showed that the char residue weight of the coatings was increased when perlite was loaded and the anti-oxidation performance was enhanced as well and MCC data indicated the addition of perlite reduced the peak heat release rate and total heat release. After the fire protection test, the results confirmed that the fire resistant time of the coating coated with 5 wt% perlite increased up to 114.4 min when the temperature of the sample boards’ backside reached 500?C.

Synergistic effect of OZrP on the combustion properties and thermal degradation behavior of intumescent flame retardant polylactide

Flame retardant polylactic acid (PLA) composites were prepared and studied using melamine phosphate (MP) as an intumescent flame retardant and organophilic alpha-zirconium phosphate (OZrP) as a synergistic agent. The flammability properties of PLA composites were investigated by UL-94 tests and microscale combustion calorimetry (MCC) experiments. It’s found that the incorporation of organically modified layered OZrP can further improve the flame retardancy of PLA composites and there exists an optimum content of OZrP. The SEM results about the char indicate that more homogeneous and compact char were formed with OZrP. In addition, the effect of OZrP on thermal degradation process of PLA composites was analyzed using in situ FTIR. The results show that the addition of OZrP decreases the onset decomposition temperature, but increases thermal stability at high temperature.

Investigation of bisphenol-substituted spirocyclic phosphazenes as cotton textile–based flame retardants

Bisphenol-substituted spirocyclic phosphazene derivatives were synthesized in 85%–94% yields and analyzed for flame retardant application to cotton fabric using Limiting Oxygen Index, Fourier transform infrared thermogravimetric analysis, differential scanning calorimetry, microscale combustion calorimetry, thermogravimetric analysis, and scanning electron microscopy. The thermogravimetric analysis methods indicate a decomposition pathway consistent for phosphorus-nitrogen-containing compounds. Levoglucosan phosphorylation and carbonaceous char formation were observed. Limiting Oxygen Index testing of these compounds on cotton-based fabrics showed improved flame resistance compared to untreated fabrics.