scholarly journals New experimental diagnostics in combustion of forest fuels: Microscale appreciation for a Macroscale approach

2018 ◽  
Author(s):  
Dominique Cancellieri ◽  
Valérie Leroy-Cancellieri ◽  
Xavier Silvani ◽  
Frédéric Morandini
Keyword(s):  
Thermal Degradation ◽  
Large Scale ◽  
Field Scale ◽  
Scanning Calorimetry ◽  
Natural Fire ◽  
Fire Propagation ◽  
New Device ◽  
Forest Fuels ◽  
Kinetics Of ◽  
Experimental Diagnostics

Abstract. In modelling the wildfire behaviour, a good knowledge of the mechanisms and the kinetic parameters controlling the thermal decomposition of forest fuel is of great importance. Lab-scale experimental diagnostics as Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Cone Calorimeter (CC) or Fire Propagation Apparatus (FPA) led to valuable results for modelling the thermal degradation of vegetal fuels and allowed several upgrades of pyrolysis models. But, these works remain beyond large-scale conditions of a wildland or forest fire. In an effort to elaborate the kinetic models under realistic natural fire conditions, a mass-loss device specifically designed for the field scale has been developed. The paper presents primary results gained using this new device, during large-scale experiments of controlled fires. The experimental data collected at the field scale lead to a new insight about thermal degradation processes of natural fuel, when compared to the kinetic laws established in TGA. These new results, provide a global description of the kinetics of degradation of Mediterranean forest fuels.

scholarly journals New experimental diagnostics in combustion of forest fuels: microscale appreciation for a macroscale approach

2018 ◽  
Vol 18 (7) ◽  
pp. 1957-1968
Author(s):  
Dominique Cancellieri ◽  
Valérie Leroy-Cancellieri ◽  
Xavier Silvani ◽  
Frédéric Morandini
Keyword(s):  
Thermal Degradation ◽  
Mass Loss ◽  
Large Scale ◽  
Kinetic Modelling ◽  
Degradation Mechanism ◽  
Morphological Characteristics ◽  
Field Scale ◽  
New Device ◽  
Forest Fuels ◽  
Experimental Diagnostics

Abstract. In modelling the wildfire behaviour, good knowledge of the mechanisms and the kinetic parameters controlling the thermal decomposition of forest fuel is of great importance. The kinetic modelling is based on the mass-loss rate, which defines the mass-source term of combustible gases that supply the flames and influences the propagation of wildland fires. In this work, we investigated the thermal degradation of three different fuels using a multi-scale approach. Lab-scale experimental diagnostics such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), use of the cone calorimeter (CC) or Fire Propagation Apparatus (FPA) led to valuable results for modelling the thermal degradation of vegetal fuels and allowed several upgrades of pyrolysis models. However, this work remains beyond large-scale conditions of a wildland or forest fire. In an effort to elaborate on the kinetic models under realistic natural fire conditions, a mass-loss device specifically designed for the field scale has been developed. The paper presents primary results gained using this new device, during large-scale experiments of controlled fires. The mass-loss records obtained on a field scale highlight the influence of the chemical composition and the structure of plants. Indeed, two species with similar chemical and morphological characteristics exhibit similar mass-loss rates, whereas the third presents different thermal behaviour. The experimental data collected at a field scale led to a new insight about thermal degradation processes of natural fuel when compared to the kinetic laws established in TGA. These new results provide a global description of the kinetics of degradation of Mediterranean forest fuels. The results led to a proposed thermal degradation mechanism that has also been validated on a larger scale.

scholarly journals The novel modeling approach for the study of thermal degradation of PMMA/nanooxide systems

2019 ◽  
Vol 38 (1) ◽  
pp. 95
Author(s):  
Mirjana Jovicic ◽  
Oskar Bera ◽  
Katalin Meszaros Szecsenyi ◽  
Predrag Kojic ◽  
Jaroslava Budinski-Simendic ◽  
...  
Keyword(s):  
Thermal Degradation ◽  
Degradation Kinetics ◽  
The Novel ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Total Mass Loss ◽  
Thermal Changes ◽  
Silica Alumina ◽  
Individual Contributions ◽  
Kinetics Of

PMMA (poly(methyl methacrylate)) nanocomposites differing in their nature, size, and surface area were prepared containing one volume percent of silica, alumina or titania. These samples and pure PMMA were prepared in order to analyze how the presence of nanooxides affects the thermal stability and degradation kinetics of the materials. A detailed study of thermal degradation and thermal changes was performed by Simultaneous Thermogravimetry and Differential Scanning Calorimetry (SDT). The proposed mathematical model, including all three heating rates in one minimizing function, well fitted all TGA data obtained with a very high coefficient of correlation. This enabled an assessment of four decomposition steps of the PMMA samples and a calculation of their activation energies and individual contributions to total mass loss. The addition of the largest nanoparticles (titania) caused the highest activation energy for each DTG stage of the PMMA/nanooxide systems. The enhancement of head-to-head H–H bonding strength was achieved by addition of alumina and titania. The influence of the size and nature of nanoparticles on the glass transition temperature of prepared PMMA systems was also determined.

scholarly journals Rheological and thermal degradation properties of hyperbranched polyisoprene prepared by anionic polymerization

2019 ◽  
Vol 6 (11) ◽  
pp. 190869 ◽  
Author(s):  
Shehu Habibu ◽  
Norazilawati Muhamad Sarih ◽  
Nor Asrina Sairi ◽  
Muzafar Zulkifli
Keyword(s):  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Diffusion Mechanism ◽  
High Vacuum ◽  
Linear Polymer ◽  
Branched Polymers ◽  
Size Exclusion ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Hyperbranched polyisoprene was prepared by anionic copolymerization under high vacuum condition. Size exclusion chromatography was used to characterize the molecular weight and branching nature of these polymers. The characterization by differential scanning calorimetry and melt rheology indicated lower T g and complex viscosity in the branched polymers as compared with the linear polymer. Degradation kinetics of these polymers was explored using thermogravimetric analysis via non-isothermal techniques. The polymers were heated under nitrogen from ambient temperature to 600°C using heating rates from 2 to 15°C min −1 . Three kinetics methods namely Friedman, Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose were used to evaluate the dependence of activation energy ( E a ) on conversion ( α ). The hyperbranched polyisoprene decomposed via multistep mechanism as manifested by the nonlinear relationship between α and E a while the linear polymer exhibited a decline in E a at higher conversions. The average E a values range from 258 to 330 kJ mol −1 for the linear, and from 260 to 320 kJ mol −1 for the branched polymers. The thermal degradation of the polymers studied involved one-dimensional diffusion mechanism as determined by Coats–Redfern method. This study may help in understanding the effect of branching on the rheological and decomposition kinetics of polyisoprene.

Estimation of Cure and Thermal Degradation Kinetics of Epoxy/Organoclay Nanocomposite

2010 ◽  
Vol 123-125 ◽  
pp. 667-670 ◽  
Author(s):  
Jae Young Lee ◽  
Bum Choul Choi ◽  
Hong Ki Lee
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Epoxy Matrix ◽  
Degradation Kinetics ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Polymer nanocomposite was synthesized through the intercalation and exfoliation of organoclay in an epoxy matrix. The epoxy matrix was composed of diglycidyl ether of bisphenol A (DGEBA, epoxy base resin), 4,4'-methylene dianiline (MDA, curing agent) and malononitrile (MN, chain extender) and organoclay was prepared by treating the montmorillonite with octadecyltrimethylammonium bromide (ODTMA). The intercalation of the organoclay was estimated by wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) analyses. In order to measure the cure rate of DGEBA/MDA (30 phr)/MN (5 phr)/Organoclay (5 phr), differential scanning calorimetry (DSC) analysis were performed at the heating rates of 5, 10, 15 and 20 oC/min, and the data was interpreted by Kissinger equation. Thermal degradation kinetics of the epoxy nanocomposite was also studied by thermogravimetric analysis (TGA). The epoxy sample was decomposed in the TGA furnace at the heating rates of 5, 10, 15 and 20 oC/min with nitrogen atmosphere of 50 ml/min. The TGA data was introduced to the Ozawa equation and the degradation activation energy was calculated according to the degradation ratio. The activation energy for cure kinetics was 43.3 kJ/mol and that for thermal degradation was 171.5 kJ/mol.

scholarly journals Partial Polymer Blend for Fused Filament Fabrication with High Thermal Stability

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3353
Author(s):  
Muhammad Harris ◽  
Johan Potgieter ◽  
Hammad Mohsin ◽  
Jim Qun Chen ◽  
Sudip Ray ◽  
...  
Keyword(s):  
Thermal Degradation ◽  
Polymer Blend ◽  
Large Scale ◽  
The Novel ◽  
Fused Filament Fabrication ◽  
Scanning Calorimetry ◽  
Factorial Anova ◽  
Novel Approach ◽  
Chemical Grafting ◽  
High Structural Stability

The materials for large scale fused filament fabrication (FFF) are not yet designed to resist thermal degradation. This research presents a novel polymer blend of polylactic acid with polypropylene for FFF, purposefully designed with minimum feasible chemical grafting and overwhelming physical interlocking to sustain thermal degradation. Multi-level general full factorial ANOVA is performed for the analysis of thermal effects. The statistical results are further investigated and validated using different thermo-chemical and visual techniques. For example, Fourier transform infrared spectroscopy (FTIR) analyzes the effects of blending and degradation on intermolecular interactions. Differential scanning calorimetry (DSC) investigates the nature of blending (grafting or interlocking) and effects of degradation on thermal properties. Thermogravimetric analysis (TGA) validates the extent of chemical grafting and physical interlocking detected in FTIR and DSC. Scanning electron microscopy (SEM) is used to analyze the morphology and phase separation. The novel approach of overwhelmed physical interlocking and minimum chemical grafting for manufacturing 3D printing blends results in high structural stability (mechanical and intermolecular) against thermal degradation as compared to neat PLA.

Electrical performance and reaction kinetics of silicone gels

1990 ◽  
Vol 5 (4) ◽  
pp. 795-800 ◽  
Author(s):  
C.P. Wong
Keyword(s):  
Reaction Kinetics ◽  
Integrated Circuit ◽  
High Performance ◽  
Large Scale ◽  
Protective Coatings ◽  
Electrical Performance ◽  
Scanning Calorimetry ◽  
Silicone Gels ◽  
Circuits Vlsi ◽  
Kinetics Of

Silicone gels are becoming more accepted as protective coatings for Very Large Scale Integrated circuits (VLSI) against severe environments due to their excellent electrical, thermal, and mechanical properties. Recent studies indicate that high performance silicone gels in low-cost, non-hermetic plastic packaging may replace conventional hermetic ceramic packaging. This paper describes the use of the soft silicone gels as coatings on Integrated Circuit (IC) devices, and the correlation between the material's cure temperature and cure time versus their adhesion and electrical reliability during 85°C, 85% RH and bias accelerating testing. In addition, the reaction kinetics of the silicone gel based on the Differential Scanning Calorimetry (DSC) study of the uncured sample will be reported.

Study of nickel-molybdenum catalysts for methanation of carbon monoxide

1980 ◽  
Vol 45 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Petr Taras ◽  
Milan Pospíšil
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Mixed Oxides ◽  
Minor Component ◽  
Fast Neutrons ◽  
Scanning Calorimetry ◽  
Low Concentrations ◽  
Γ Rays ◽  
Molybdenum Catalysts ◽  
Kinetics Of

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

scholarly journals Thermal Degradation Kinetics and Modeling Study of Ultra High Molecular Weight Polyethylene (UHMWP)/Graphene Nanocomposite

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1597
Author(s):  
Iman Jafari ◽  
Mohamadreza Shakiba ◽  
Fatemeh Khosravi ◽  
Seeram Ramakrishna ◽  
Ehsan Abasi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Thermal Degradation ◽  
High Molecular Weight ◽  
Degradation Kinetics ◽  
Graphene Nanosheets ◽  
Thermal Degradation Kinetics ◽  
Graphene Nanocomposites ◽  
Kinetics Of ◽  
Ultra High Molecular Weight

The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (Ea) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content.

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