Mass Loss Temperature Research Articles

The Effect of Mixing Ratio and Fuel Purity on Smoke and Burning Characteristics of N-heptane/Toluene Test Fire

Abstract Experiments were conducted in a fire test room to investigate soot particle and burning behavior of n-heptane/toluene mixtures blended by liquids in different mixing ratio and different purity. Analytical reagent n-heptane (AR, purity ≥ 99.5 %), chemically pure n-heptane (CP, purity ≥ 97 %) and toluene (purity ≥ 99.5 %) were selected to prepare four kinds of mixtures, mixing by volume and by mass were two modes available. Extinction coefficient of smoke was obtained by extinction meter on the room ceiling. Size distribution of soot particles was measured by fast particulate spectrometer DMS500, then count median diameter (CMD) and geometric standard deviation of diameter (GSD) were calculated. Mass loss curve and temperature profile were measured by electronic balance and thermocouples, respectively. Experimental results revealed that even small difference in the incorporation of toluene, such as mixed by volume and mixed by mass, had significant influences on smoke extinction and CMD. When fuels were mixed in a same mass ratio, slight gap in purities could also affect smoke extinction. Thus fuels mixed by mass could not be employed as test fire, while CP n-heptane could be selected to prepare fuels of test fire based on our preliminary results. As for burning behavior, temperature profiles were almost identical for all mixtures, mass loss curves also had good consistencies.

Bis-phenylethynyl polyhedral oligomeric silsesquioxanes: new high-temperature, processable thermosetting materials.

Bis-phenylethynyl polyhedral oligomeric silsesquioxane (bis-PE-POSS) compounds were synthesized and thermally cured yielding crosslinked materials. After curing at 370 °C, thermal decomposition occurs near 600 °C under nitrogen. These materials were synthesized by condensation of a new phenylethynyl-functional dichlorosilane onto tetrasilanol phenyl POSS, yielding two geometric isomers.

Wind Tunnel Experiments to Study Chaparral Crown Fires.

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.

A case for closed-loop recycling of post-consumer PET for automotive foams

Striving to utilize sustainable material sources, polyester polyols made via glycolysis and esterification of recycled polyethylene terephthalate (rPET) scrap were used to synthesize flexible polyurethane (PU) foams typically found in automotive interior applications. The objective of this endeavor was to ascertain if a closed-loop model could be established with the discarded PET feedstock. In five separate formulations, up to 50% of the total polyol content (traditionally derived from petroleum-based feedstock) was replaced with the afore-mentioned sustainable recycled polyols. These foams underwent mechanical, thermal, morphological, and physical characterization testing to determine feasibility for use in an automotive interior. Young’s modulus, tensile stress at maximum load, tear resistance, and compression modulus all increased by combined averages of 121%, 67%, 32%, and 150% over the control petroleum-based formulation, respectively, in foams possessing 50% rPET polyol content. Thermal stability also increased with sustainable polyol content; thermogravimetric analysis showed that 50% mass loss temperature increased by an average of 20 °C in foams containing 30% recycled polyol. Properties of density and SAG factor remained within 5% of the control petroleum-based reference foams. After comparing these findings to traditional polyols, a compelling argument can be made for the use of post-consumer automotive and industrial feedstocks in developing high-performing interior automotive PU foams.

Moisture absorption and mechanical properties of chemically modified linen/polypropylene composites

To decrease the moisture absorption and improve the mechanical properties of linen/polypropylene(PP) composites, linen was modified with silane N-[3-(trimethoxysilyl) propyl]ethylenediamine(AAPTS), surfactant tri-methyloctadecylammonium bromide(STAB), and both AAPTS and STAB, respectively. Fourier transform infrared(FTIR) spectra showed that the linen was successfully modified and alkyl chains were attached through different treatments. The linen and PP were compounded by melt compressing. The moisture absorption of linen was decreased after STAB and AAPTS-STAB modifications. The moisture absorption, mechanical property and thermal property of the composites were also characterized. The results show that the moisture absorption of the AAPTS-modified linen(F1) reinforced PP(PPF1) is 8.09%, which is higher than that of the unmodified linen reinforced PP(PPF)(7.89%). The moisture absorption of the STAB-AAPTS-modified linen(F3) reinforced PP(PPF3) is 6.58%. The tensile strengths of PPF1 and PPF3 are 33.7 and 35.8 MPa, which are improved by 22.5% and 30% compared with that of PPF(27.5 MPa), respectively. Nevertheless, the moisture absorption of the STAB-modified linen(F2) reinforced PP(PPF2) is decreased by 22.4%, and the tensile strength is improved by 30% compared with those of PPF. Scanning electron microscopy(SEM) analysis of the fractured surface confirms the good interfacial adhesion of PPF2 compared with those of other composites. Furthermore, the 5% mass loss temperatures of the composites are all higher than 290 °C. Thus, linen modified with STAB is a promising reinforcement for biocomposites.

A study to investigate pyrolysis of wood particles of various shapes and sizes

Pyrolysis of centimeter-scale wood particles of various sizes and shapes needs to be understood to determine their burning rate and life. Such particles may be thought of as firebrands, which are a major reason for spotting ignition in wildland and wildland-urban interface fires. The burning lifetime of firebrands controls the maximum distance they can travel to cause spotting. To understand and model this, experiments are done in a vertical tube furnace with wood particles of different sizes and shapes. For computations, two classes of shapes, prolate and oblate ellipsoids, were chosen to represent the arbitrary geometry of such particles. Prolate ellipsoids include shapes ranging from thin needles to spheres, whereas, oblate ellipsoids include shapes ranging from thin disks to spheres. The choice of these smooth shapes, while facilitating expedient computations also enables the coverage of wide ranges of particle shapes and surface area to volume ratios (SVR). Model simulations show satisfactory agreement with relevant literature and experimental data. Particle aspect ratio (ϵ, the ratio of minor and major axes), SVR, and equivalent radius (Re) are used to define the particle geometry. Mass loss and center temperature profiles are presented and discussed. It is shown that with the decreasing of aspect ratio, wood particle decomposes faster and the final char fraction becomes smaller. A power-law based correlation between conversion time (tcon) and SVR is derived and verified against experiments. Further, it is shown that an increase in the SVR enhances the production of tar and decreases the yield of char while leaving the yield of gas mostly unaffected.

Experimental study on fire behaviors of external thermal insulation composite system under vertical radiation

SummaryUsing a vertical thermal radiator, we perform a set of experiments on the external thermal insulation composite system (ETICS) and pure extruded polystyrene (XPS). Several important parameters, including time to ignition, mass loss, and sample temperature, were measured. The combustion degree of XPS used during the experiments was B1 and B2. Results show that the whole burning process can be divided into 3 typical stages. Because of the protection effect of the outer layer of ETICS, the burning process of ETICS was noticeably different from that of pure XPS. The experimental results indicated that the protection effect of the outer layer weakened the difference between B1 and B2 flame‐retardant XPS. The time to ignition was increased under the effect of outer layer, while the core material (XPS) was easier to be ignited when the outer layer falls out. The research results are useful to the theoretical and numerical study on the fire characteristics of foamed polymer under vertical thermal radiation condition.

Relation between composition and vacant oxygen sites in the mixed ionic-electronic conductors La5.4W1−yMyO12−δ (M = Mo, Re; 0 ≤ y ≤ 0.2) and their mother compound La6−xWO12−δ (0.4 ≤ x ≤ 0.8)

A detailed analysis of specimen composition, water uptake and their interrelationship in the systems La6‐xWO12‐δ (0.4≤x≤0.8) and La6‐xW1-yMyO12‐δ (0≤y≤0.2; M=Mo, Re) is presented. The three specimen series were investigated in dry and wet (D2O) conditions. A systematic trend in mass loss and onset temperature variation was observed in La6‐xWO12‐δ (0.4≤x≤0.8). Even very small amounts (<1wt%) of secondary phases were found to notably modify the specimen's water uptake and onset temperature of mass loss. The theoretical model for vacancy concentration available was used to calculate the vacant oxygen sites starting from mass loss values determined by thermogravimetry. A discrepancy between the calculated and observed concentration of vacant oxygen sites is observed for all three systems. The effect of substitution of W by Re or Mo on the vacancy amount is explained taking into account diffraction measurements and information on the oxidation state of the substituting elements Mo and Re.

Simultaneous improvements in flammability and mechanical toughening of epoxy resins through nano-silica addition

Polymers in transport, and many other engineering applications, are required to be mechanically tough as well as resistant to ignition and flame spread. These demands are often for many polymer types in competition, especially when adding flame retardants. With nano-silica addition, we show that improvements in both properties of a polymer can be achieved simultaneously. In this study, an epoxy resin is evaluated for its flammability and mechanical properties with step wise additions of nano-silica. The fracture toughness was significantly improved. In the single edge notch bending test, the addition of 36% nano-silica particles doubled the toughness and increased the flexure modulus by 50%. Flammability was studied via time to ignition at constant irradiation, and via a UL94 test coupled with mass loss and surface temperature measurements. Modelling for the heat transport and chemical kinetics in Gpyro was done and yielded good agreement with the temperatures measured. Adding up to 36% nano-silica, the time to ignition increased by 38% although a sharp decrease was observed around 24% SiO2 addition. We show that the increased time to ignition is mostly due to a higher thermal diffusivity, increased inert content, as well as a strengthening of the residue outer skin, which acts as a mass barrier for pyrolysate. This outer skin was analysed using a scanning electron microscope coupled with an energy dispersive X-ray spectrometer. We found that in the skin the nano-silica particles agglomerate at the surface forming a strong continuous structure together with the char residue from the epoxy. Improvements in the flammability as seen in the UL94 test were measured with mass loss showing a 30% reduction after 20s, and surface temperatures at the ignited end being up to 75K lower compared to the pure epoxy. Modelling in Gpyro supported the temperature measurements taken. Despite the improvements seen, all samples ignited, failing the test with dripping and showing that the improvements recorded in time to ignition did not fully translate over to the UL94 test. Overall we show that the flammability and toughness of epoxy could be improved simultaneously with nano-silica. Using up to 36% nano-silica, the significant modification of thermal properties could be explored in relation to fire properties for epoxy. Increasing the thermal diffusivity as well as skin formation are the main parameters improving the flammability and show a path for potential improvements in other composites as well.

Effect of oxygen concentration on the combustion of horizontally-oriented slabs of PMMA

The aim of this study is to collect data on the combustion of horizontally-oriented poly(methyl methacrylate) (PMMA) samples in reduced oxygen atmospheres for CFD model validation. Experimental results relating the oxygen concentration to the burning behavior of 3-cm-thick clear PMMA slabs are discussed. Experiments are conducted in the controlled atmosphere calorimeter of IRSN called CADUCEE. Pyrolysis and combustion of 0.2×0.2m2 horizontally-oriented PMMA samples are studied varying the oxygen molar fraction from 0.210 to 0.180, extinction occurring at about 0.175. The measured quantities are the regression rate of the slab, mass loss rate, temperatures and total and radiative heat fluxes at the center of the slab. All experiments are carried out twice, showing a good repeatability. It is found that the slab regression rate, mass loss rate and heat fluxes at the slab center decrease significantly with the oxygen concentration, while the gas temperature is much less sensitive. Most notable is that the radiative and convective contributions to the total heat flux remain almost constant, respectively 0.65 and 0.35. It is also found that both heat fluxes and mass loss rate exhibit linear oxygen-concentration-dependent behavior. From an energy balance and current average values of the total heat flux and regression rate at the center of the slab, the present study obtains a heat of gasification value of 2.25MJkg−1, in agreement with literature data.

A novel approach for assessment of thermal stability of organic azides through prediction of their temperature of maximum mass loss

Organic azides contain covalent azide groups, which can decompose with the slightest input of energy from heat and light. A novel, reliable and simple method is introduced to predict the temperature at which maximum of mass loss for organic azides (T dmax) was occurred. It requires only molecular structure of a desired organic azide without using computer codes and complex molecular descriptors. The new model is based on the presence of several molecular fragments as well as the contribution of the number of hydrogen and nitrogen atoms. Experimental data of 53 organic azides containing various molecular structures are used to derive new correlation. Statistical parameters including root mean squared deviation, mean absolute error and maximum of errors of the new model are 8.49, 6.99 and 18.11 K, respectively, which confirm high reliability of the new method. The method has been tested for further five organic azides including complex molecular structures, which give good results.

Combustion properties of saturates, aromatics, resins, and asphaltenes in asphalt binder

To further understand combustion properties of asphalt binder at the component level, four components such as saturates, aromatics, resins, and asphaltenes (SARA) were first separated from asphalt binder. Then thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) was used to study combustion properties and released volatiles of each SARA fraction, and microscopic morphology characteristics of combustion residues were observed. The results indicate that the contents of aromatics and resins are higher than those of saturates and asphaltenes. The combustion process of each SARA fraction contains two main mass loss stages. Also, there are obvious differences among SARA fractions in combustion temperature range, maximum thermal mass loss temperature, mass loss percentage and mass loss rate in each combustion stage. The thermal properties becomes more and more stable from saturates to asphaltenes. The main combustion temperature ranges of SARA fractions show obvious gradient distribution characteristics from low to high temperature. Additionally, the volatiles released from each SARA fraction are composed of different kinds of hydrocarbon compounds and gaseous products. There are larger differences in volatile constituents in different combustion stages of each SARA fraction. However, the carbon dioxide and water are always two main products in different combustion stages of each SARA fraction. Finally, the charring layer integrity after combustion of SARA fractions becomes better and better from saturates to asphaltenes. It is believed that the combustion properties of asphalt binder are further understood at the component level.

Highly efficient flame-retardant epoxy resin with a novel DOPO-based triazole compound: Thermal stability, flame retardancy and mechanism

A novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based triazole compound (DTA) was prepared by reacting DOPO with imine obtained from the condensation of terephthalaldehyde with 3-amino-1H-1,2,4-triazole. Its chemical structure was characterized by FTIR, 1H NMR, 13C NMR, 31P NMR and elemental analysis. DTA was used as co-curing agent to improve the flame retardancy of epoxy resin. The thermal stabilities and flame-retardant properties of epoxy thermosets were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 test. Moreover, the flame-retardant mechanism was investigated by FTIR, Py-GC/MS, SEM, elemental analysis and Raman spectroscopy. The results revealed that the addition of DTA resulted in the decrease of 5 wt% mass loss temperature of epoxy thermoset. With triazole ring and DOPO group in the molecular structure, DTA possessed superior flame-retardant efficiency. The thermoset modified with 4 wt% DTA achieved an LOI value of 34.8% and V-0 rating in UL-94 test, where the phosphorus content was only 0.34 wt%. Impressively, all modified thermosets showed blowing-out effect during combustion, which resulted from the concentrated release of pyrolytic gases containing phosphorus-based radicals and nonflammable gases. The flame-retardant mechanism was ascribed to the barrier effect of phosphorus-rich char layers with polyaromatic structures in the condensed phase, and quenching effect of phosphorus-based radicals and diluting effect of nonflammable gases in the gas phase.

Crude oil characterization using TGA-DTA, TGA-FTIR and TGA-MS techniques

In this research, combustion characterization and kinetics of four different origin crude oil samples were determined using thermogravimetry - differential thermal analysis (TGA-DTA) and thermogravimetry - Fourier transform infrared (TGA-FTIR) and thermogravimetry – mass spectrophotometry (TGA-MS) techniques.In the TGA-DTA analysis of crude oil samples, low temperature oxidation (LTO) and high temperature oxidation (HTO) reaction regions were observed in different temperature intervals. On the other hand, reaction regions, mass loss, and peak-burnout temperatures of the crude oil samples were also determined using TGA-DTA curves. In TGA-FTIR analysis, spectrums of crude oil samples were examined at different time intervals and composition of several hydrocarbon compounds was determined quantitatively. This research was also focused on the main volatile products (H2, H2O, CO, CO, C6H6, SO2 etc…) of different origin crude oil samples on the basis of both their relative intensities and on their relevancy by using TGA-MS technique.Two different Arrhenius types of kinetic models were used in order to determine the kinetic triplets (activation energy, Arrhenius constant and reaction order) of crude oil samples studied. It was observed that in HTO region, higher activation energy values were observed depending on the °API gravities of the crude oils.

Structural modifications of cellulose samples after dissolution into various solvent systems

This work deals with the modifications resulting from the dissolution of four commercial cellulosic samples, with different crystallinity rates and degrees of polymerization (DPs), in four solvent systems, known and used to dissolve cellulose. The dissolution conditions were optimized for the 16 various systems and followed by turbidity measurements. After regeneration, the samples were analyzed by thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffractometry (XRD) to study their modification. Viscosimetry measurements were used to evaluate the potential decrease of the DP after dissolution. The observed structural modifications established that, for low DP, all the solvent systems were efficient in dissolving the cellulose without altering the DP, except BMIM [Cl], which provoked a decrease of up to 40% and a decrease of around 20% of the degradation temperature (onset temperature, T o). For high molecular weight (MW) celluloses, DMSO/TBAF was the only system to allow a complete dissolution without any molar mass loss and degradation temperature modification.

Self-extinction of timber

Self-extinction of timber after the removal of an external incident heat flux is necessary to ensure that structures with exposed wood do not contribute to a fire after the building contents are fully consumed. Two series of tests with solid wood and cross-laminated timber were conducted to study the conditions leading to self-extinction. The heat fluxes and heating duration were varied systematically. For each test, the evolution of the in-depth temperature distribution was measured using thermocouples while the mass loss rate was measured using a load cell. The experiments were allowed to reach a steady-state mass loss rate. The in-depth temperature gradient, which represents in-depth heat losses from the pyrolysis zone, was calculated from thermocouple measurements until it reached steady-state. As the external incident heat flux increases, the mass loss rate as well as the in-depth thermal gradient reach a steady-state value. Once the steady-state mass loss rate and temperature gradient were attained, the external heat flux was removed and the flame was allowed to extinguish. Over the entire range of heat fluxes (30–100kW/m2) and heating periods used in the tests, and for all the wood types used, self-extinction was observed.

In situ polymerization of modified graphene/polyimide composite with improved mechanical and thermal properties

The graphene oxide was modified by coupling agent (KH-550). The polyimide/graphene treated by KH-550 (PI/KG) composite were prepared by in situ polymerization from 4,4′-diaminodiphenyl ether (ODA), 2,2-bis(4- (3,4-dicarboxyphenoxy) phenyl) propane dianhydride (BPADA), and modified graphene. The structure and morphology of the composite membranes were analyzed by Fourier transform infrared spectroscopy (FT-IR) and X ray diffraction. Compared to pure PI system, the tensile strength and elongation at break of PI/KG-4 composite, increasing by 26.4 and 24.1 %, was 134 MPa and 9.8 %, respectively. The 5 % mass loss temperature of polyimide system was about 486.1 °C, and the PI/KG-6 composite was 493.8 °C. PI/KG composites have a better thermal stability and a higher thermal conductivity compared to PI system with the increasing of KG content.

1,3-Dipolar cycloaddition 반응을 통해 기능화된 carbon nanotube 표면 위에 균일계 촉매 담지 및 에틸렌 중합

− In this study, CNT functionalized with pyrrolidine ring via 1,3-dipolar cycloaddition reaction with various amino acid and aldehyde was synthesized. Metallocene was subsequently immobilized on the functionalized CNT and CNT/polyethylene composite was prepared via in-situ ethylene polymerization. The polymerization activities of metallocene supported on CNT functionalized with glycine and benzaldehyde (Gly+BA-CNT) were similar to those of metallocene supported on CNT functionalized with N-benzyloxycarbonylglycine and paraformaldehyde (Z-Gly+PFA-CNT) although its Zr content was lower than that of Z-Gly+PFA-CNT. In the case of metallocene supported on Z-Gly+PFACNT, the even distribution of active sites hindered the diffusion of ethylene monomer and cocatalyst MAO due to steric hindrance during ethylene polymerization. Compared to polyethylene produced from homogeneous metallocene catalysts, CNT/PE composites had a higher initial degradation temperature (T onset ) and maximum mass loss temperature (T max ). It suggests that pyrrolidine functionalized CNT is uniformly dispersed and strongly interacted with the PE matrix, enhancing the thermal stability of PE.

Study of the synergistic effect of nickel phosphate nanotubes (NiPO-NT) on intumescent flame retardant polypropylene composites

The nickel phosphate nanotubes (NiPO-NT) were synthesized by hydrothermal method, and its structure was characterized. Then NiPO-NT was added to intumescent flame retardants system in polypropylene (PP) matrix for the first time,and the synergistic effect of NiPO-NT with intumescent flame retardants was studied. The results show that only small content of NiPO-NT can obviously improve the flame retardant and thermal properties of intumescent flame retardant PP composite. With the addition of 0.3 % NiPO-NT, the peak heat release rate of intumescent flame retardant PP composite decreases from 374.7 to 255.5 kW m−2, and the limit oxygen index value increases from 29.9 to 33.9. Meanwhile, the maximum mass loss temperature under N2 atmosphere is increased from 408 to 483 °C.

Flame Retardant Medium-Density Fiberboard with Expanded Vermiculite

This study investigated the effect of expanded vermiculite (EV) on the flammability properties of medium-density fiberboard (MDF), which was evaluated by limiting oxygen index (LOI) and simultaneous thermal analysis (TG-DSC). In addition, the modulus of rupture (MOR) and the modulus of elasticity (MOE) of the samples were studied. The results indicated that the addition of EV increased the LOI of MDF, while it decreased the MOR and MOE of MDF quite rapidly. The TG data showed that the fiber-charring rate of the fire retardant MDF increased sharply, more than 10 times that of untreated MDF. Moreover, with increasing of the ratio of the EV and fiber (V/F), it increased the fiber-charring rate of the MDF sharply, decreased the temperature of the maximum mass loss, and decreased the maximum mass loss rate of MDF. The DSC test results indicated that the total temperature range of the exothermic stage had extended and that the first peak in the exothermic stage decreased rapidly with increasing of V/F ratio.