Mass Loss Temperature Research Articles

Novel adamantane-based dicyanate ester: Synthesis, polymerization kinetics, and thermal properties of resulting polymer

A new adamantane-based dicyanate ester has been synthesized. The kinetics of its thermal polymerization is studied by means of conventional and temperature-modulated differential scanning calorimetry. The kinetics is analyzed comprehensively by a combination of an advanced isoconversional and model-fitting method. Polymerization proceeds via transition from a kinetic- to diffusion-control regime, which becomes operative at the later stages of the process. The kinetically-controlled regime manifests itself as a quasi-one-step auto-catalytic reaction. A contribution of diffusion to the overall kinetic is accounted for by means of the Fournier model. The polymerization product possesses excellent thermal properties (the glass transition temperature of ∼370 °C and 5% mass loss temperature of ∼480 °C), which makes it a promising candidate for application in hot-section components for aerospace and military industry.

Poly(arylene ether sulfone) containing diphenyl-biphthalazin-dione moieties with excellent thermal resistance

A series of novel poly(arylene ether sulfone)s containing diphenyl-biphthalazin-dione moieties (PPDESs) are synthesized from 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 4,4′-dichlorodiphenyl sulfone and diphenyl-biphthalazin-dione. Structural analyses such as NMR, FT-IR, instinct viscosity and XRD, as well as property tests including TGA, DSC, DMA, solubility and mechanical properties were carried out on PPDESs. The Tg of PPDESs is up to 388 °C, suggesting that PPDESs show excellent thermal resistance. The 5% mass loss temperature (Td5) of PPDESs is up to 513 °C. PPDESs possess excellent mechanic and thermo-mechanical performance which Young's modulus above 1.95 GPa, the tensile strength up to 107 MPa and the storage modulus retention up to 51.6% at 300 °C. Additionally, PPDESs exhibit an appropriate solubility in organic solvents such as chloroform, 1,1,2,2-tetrachloroethane, N-methyl pyrrolidone and so on. With the increasing introduction of the diphenyl-biphthalazin-dione, the thermal resistance and mechanical properties of PPDES are improved, while the solubility is slightly reduced.

Characterization of combustion behavior of commercial flame-retardant plywoods in fire propagation apparatus

This paper deals with the combustion behavior and thermal decomposition of two typical kinds of plywoods used in composite floor. The experimental study was performed in fire propagation apparatus and combustion parameters including ignition time, heat release rate, mass loss rate and effective heat of combustion were analysed. The results show that the risk of ignition and heat release of alder is higher than that of Huang Jin Guo Mu under most heat fluxes. Three thermal decomposition stages are proposed according to the characteristics of mass loss rate and temperature profiles. The present work provides input parameters for numerical modeling and gives guidance for fire risk assessment of rail transit.

Effects of Geographic Region and Cultivar on Fatty Acid Profile and Thermal Stability of Zanthoxylum bungeanum Seed Oil.

Fatty acid profile and thermal stability of 7 varieties zanthoxylum bungeanum (GZF, GDJ, CJJ, SHY, SMN, SJY, GTS) seed oils (ZBO) were studied. Fatty acid profile, thermal stability were determined using gas chromatography equipped with flame ionization detector (GC-FID) and thermogravimetry analysis (TGA), respectively. Chemical properties, total phenolics and antioxidant activities of ZBO were determined as well. Palmitoleic acid and oleic acid (OA) were the dominant fatty acids, the ratio of ω-6/ω-3 polyunsaturated fatty acids (PUFA) of ZBO ranged from 0.66 ± 0.01 to 1.17 ± 0.01, seven varieties ZBO showed a higher thermal stability, with the 50% mass loss temperature ranged from 397.35 ± 4.02°C to 412.50 ± 2.35°C, GZF seed oil showed a balance fatty acid profile, the ratio of ω-6/ω-3 PUFA was 0.90 ± 0.01, GDJ seed oil showed a higher thermal stability, which the 50% mass loss temperature was 412.50 ± 2.35℃. These results suggested that fatty acid profile and thermal stability of ZBO were affected by cultivars and geographic region, and it may serve as a functional dietary oil.

Synthesis and characterization of a pyrene-based Schiff base and its oligomer: Investigation of fluorescent Cr3+ probe

In this study, a unique Schiff base (SP) was synthesized from 1-aminopyrine (1-AP) and salicylaldehyde (SA) compounds. The obtained oligomer of this Schiff base was carried out by the oxidative polymerization method. The structural characterizations of 2-((pyren-1-yl-imino)methyl)phenol (SP) and oligo-2-((pyren-1-yl-imino)methyl)phenol (OSP) by FT-IR, 1H NMR and 13C NMR measurements, electrochemical properties by cyclic voltammetry (CV); optical properties by UV/Vis studies and photoluminescence (PL) spectrophotometry; thermal stability were performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The molecular weight of the obtained oligomer was determined using gel permeation chromatography (GPC). Accordingly, Mn and Mw values of OSP were found to be 2800 and 3150 Da, respectively. The imine bond provided the structures with high thermal stability, and the maximum mass loss temperatures (Tmax) of SP and OSP were found to be 350 0 and 343 °C, respectively. PL study showed that SP could be used as a Cr3+ sensor among a series of metals. The results revealed that the limit of detection (LOD) value of SP was 1.03 × 10−9 M and was not affected by other ions in the environment.

Experimental Study on Rubbing Wear Characteristics of Labyrinth Seal With Trapezoidal Fins

AbstractThe wear characteristics of the trapezoidal fin against high-speed rotor were experimentally investigated at different final incursion depths, incursion rates, and sliding velocities. To characterize the geometrical effect, a small specimen (SS) and a large specimen (LS) were selected to analyze the mass loss, wear geometry, contact forces, and frictional temperature distributions under different conditions. The results show that the contact-separation is most likely to occur between the trapezoidal fin and rotor. In the rubbing process, the plastic deformation is dominating, and the abrasive and adhesive wears have pronounced effects on the wear behavior of the rubbing interface. The wear performance of the SS is sensitive to the structure imbalance, which induces the combined mushrooming and bending damage in the trapezoidal fin. However, the symmetrical mushrooming damage is generated in the LS. For both SS and LS, the mass loss is decreased with increasing incursion rate and sliding velocity, and the mass loss percentage is pronounced at the early stage of rubbing. The averaged friction coefficient is 0.1–0.16 for the LS whereas 0.1–0.19 for the SS. The peak frictional temperature is 560–640 °C for the LS, while 360–400 °C for the SS. The contact-separation significantly reduces the effects of final incursion depth, incursion rate, and sliding velocity on the wear geometry, contact forces, and temperature rise in the trapezoidal labyrinth fin.

Evaluation of models and important parameters for firebrand burning

Understanding the parameters that affect firebrand burning conditions is needed to quantify and model heat transfer from firebrands to combustible surfaces. In this research, an experimental and analytical effort was conducted to determine the variable relationships that control firebrand burning. A series of experiments were performed to quantify the mass loss rate, temperature, and char diameter change with time for single and arrays of cylindrical firebrands. An analytical model was developed to predict the time dependent burning of firebrands including ash accumulation in forced flow conditions. Six different methods for predicting char oxidation were included in the model to identify the best approach for predicting firebrand burning. Based on the simulation results, the model with char oxidation determined using the heat and mass transfer Reynolds analogy provided the best results with predicted temperatures, char diameter, and mass loss rates within 5%, 4%, and 29% of the single firebrand test data, respectively. Higher differences were predicted with arrays of firebrands, which was attributed to the complex flow field that develops around the firebrands. Analysis of the analytical equations was used to identify the variable relationships affecting firebrand temperature, mass loss rate, char diameter, and burning duration.

Preparation of Triple-Functionalized Montmorillonite Layers Promoting Thermal Stability of Polystyrene.

The objective of this study was to investigate the effect of three different treatments on the morphology, microstructure, and the thermal characteristics of a montmorillonite (Mt) sample, by using hydrochloric acid (HCl), tributyl tetradecyl phosphonium chloride (TTPC) surfactant, and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The resultant nanofillers were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption analysis, X-ray fluorescence spectrometry (XRF), and thermogravimetric analysis (TGA). The results showed that the amount of chemical grafting of the γ-MPS was increased after the acid treatment, whereas the amount of intercalation of the TTPC surfactant was decreased. The preintercalation of TTPC or silylation of γ-MPS, for the Mt sample, had a certain hindrance effect on its subsequent silylation or intercalation treatments. Furthermore, the effect of four different nanofillers on the thermal stability properties of the polystyrene (PS) matrix were also investigated. The results showed an increase in thermal stability for the triple-functionalized Mt, compared with the double-functionalized samples. The onset decomposition temperatures and the maximum mass loss temperatures of the PS nanocomposites were increased by 27 °C and 32 °C, respectively, by the incorporation of triple-modified Mt, as a result of the good exfoliation and dispersion of the nanolayers, more favorable polymer–nanofiller interaction, as well as the formation of a more remarkable tortuous pathway in the continuous matrix.

Mass loss implementation and temperature evolution of very massive stars

AbstractVery massive stars (VMS) dominate the physics of young clusters due to their extreme stellar winds. The mass lost by these stars in their winds determine their evolution, chemical yields and their end fates. In this contribution we study the main-sequence evolution of VMS with a new mass-loss recipe that switches from optically-thin O star winds to optically-thick Wolf-Rayet type winds through the model independent transition mass loss.

Temperature-dependent properties of corroded super ductile TMT steel bars

Super ductile TMT reinforcing steel bars are commonly used these days for RC constructions, given their excellent thermal properties. SD TMT rebars are superior due to their distinct cross-sectional phase distribution (CSPD) of martensite, bainite, and pearlite. This paper investigates the influence of the superimposition of corrosion-induced damage by the exposure to elevated temperatures on properties of reinforcing steel simulating corroded structural members exposed to an accidental fire. The experimental program involved exposing bare bars to accelerated corrosion to achieve desired corrosion levels in terms of mass loss using the impressed current accelerated corrosion technique to a precision level of ± 1%. Subsequently, the identical specimens were heated to 250 °C, 550 °C, 800 °C, and 950 °C and allowed to achieve a steady-state at that temperature before being cooled down to ambient temperatures in the furnace itself and tested in tension to failure. A detailed analysis of the effect of various combinations of corrosion-induced mass loss and elevated temperatures on ductility characteristics of reinforcing steel using various prevalent methods in the available literature is presented. The results indicate a notable reduction in reinforcing steel's critical mechanical properties due to the superimposition of the two phenomena.

Syntheses and properties of novel polyarylates with ethyl units as a side group

A series of polyarylates (PAHAs) with ethyl pendent groups were synthesized from 2,2-bis (4-hydroxyphenyl) propane, bisphenol and two different benzenedicarbonyl chlorides through interfacial copolymerization. The structures and aggregation states of the copolymers were confirmed by FT-IR, 1H NMR and XRD. The resultant polyarylates have excellent thermal properties with the glass transition temperature of 196.2–196.9 °C and the 5% mass loss temperature of 437.6–458.5 °C. Because of the introduction of ethyl pendent groups, the transmittance at 400 nm and 450 nm of polymer films can reach up to 84.86–85.20% and 85.75–86.52%. The cut-off wavelength was in the range of 309–314 nm, lower than that of commercial product U-100. The results of rheology properties testing suggest the viscosity of PAHAs decreased from 16720 to 617.1 Pa·s under 285–310 °C with the incorporation of ethyl pendent groups. Meanwhile, when the test time was extended to 30 min at 310 °C, the complex viscosity of PAHAs had almost no change, indicating the exceptional melt flowability and stability of polyarylates PAHAs. That is beneficial for the application of its melt process such as injection molding, especially for thin wall products.

Influence of Stairwell Ventilation State on Fire Behavior and Smoke Temperature Distribution in a Full-scale High-rise Building

In this study, a set of experiments were carried out in a 21-story full-scale building varying stairwell ventilation state to investigate the fire behavior and smoke temperature distribution in the stairwell. Results demonstrate that the ventilation state of top vents has a great influence on the fire behavior and smoke temperature distribution than the bottom vents. The flame inclines to the stairwell with top vents open during the steady stage, while with top vents closed, it just tilts slightly to the side wall. The mass loss rates and temperature attenuations with top vents closed are larger than those with top vents open. In addition, the open of bottom vents can cause a reduction in the smoke temperature. These unique full-scale experiments provide crucial experimental data that help the design of safer smoke ventilation systems for stairwells in a high-rise building.

Experimental research on gypsum-based mixtures containing recycled roofing tile powder at ambient and high temperatures

In this study, the properties of gypsum-based pastes and mortars containing recycled tile powder were investigated at ambient and high temperatures. For this purpose waste tiles were collected from demolition sites and ground. Two different sample groups, namely gypsum pastes and gypsum mortars, were produced. Both groups had their own reference sample that was produced using only gypsum, in addition to samples that were modified by using 10%, 20% and 30% recycled tile powder. The samples were exposed to 600 °C and 800 °C. Unit weights, mass losses, ultrasonic pulse velocities, bending strengths, compressive strength, volume changes and visual investigations were performed on the samples before and after they were exposed to the high temperatures. In addition, the apparent porosity, water absorption and thermal conductivity of the recycled tile powder containing gypsum-based mixtures were investigated. In order to investigate the microstructural changes of the mixtures, scanning electron microscopy examinations and XRD analyses were performed. The findings showed that the strength of the mixtures decreased with the addition of recycled tile powder. The apparent porosity and water absorption of the mixtures were found to increase. However, the presence of recycled tile powder enhanced mass loss, thermal conductivity and high temperature resistance. Furthermore, the volume changes resulting from high temperatures were significantly reduced by using the recycled tile powder.

Pyrolysis characteristics of cellulosic biomass in the presence of alkali and alkaline-earth-metal (AAEM) oxalates

The pyrolysis characteristics including reaction kinetics and products distribution of cellulose pyrolysis in the presence of AAEM oxalates were preliminarily studied by using the TG and PY-GC/MS analysis. In general, the main mass loss region took place at 300–400 °C and the maximum mass loss temperature was about 380 °C. The activation energy Ea of cellulose pyrolysis (159 kJ/mol) was decreased in the presence of AAEM oxalates (K2C2O4—123 kJ/mol, MgC2O4—151 kJ/mol and CaC2O4—138 kJ/mol). The major pyrolytic components were classified into furans, anhydrosugars, acids, esters, alcohols, aldehydes, pyrans, ketones, hydrocarbons and phenols, etc. The presence of AAEM oxalates promoted the generation of ketones. In particular, K2C2O4 and MgC2O4 showed a high selectivity (relative content: > 30%) on the production of ketones. As a good candidate of MgO, MgC2O4 or MgCO3 has a high potential for both gas upgrading and porous carbon production in biomass pyrolysis.

Hydration and cooling in elite athletes: relationship with performance, body mass loss and body temperatures during the Doha 2019 IAAF World Athletics Championships

PurposeTo characterise hydration, cooling, body mass loss, and core (Tcore) and skin (Tsk) temperatures during World Athletics Championships in hot-humid conditions.MethodsMarathon and race-walk (20 km and 50 km) athletes (n=83,...

Markedly Different Decomposition Temperature and Products of Biomass Pyrolysis at Low Temperature—Differentiation of Acids in Their Effects on Pretreatment

Pine as a softwood and poplar as a hardwood pretreated with hydrochloric acid (HCl), phosphoric acid (H3PO4), and hypophosphorous acid (H3PO2) are studied for the pyrolytic properties and products in thermogravimetry (TG) and fixed bed reactor. The pyrolysis performances are pronouncedly distinguished due to the compositional and structural changes induced by the acid pretreatments. Reduction in the mineral content in the biomass feedstocks by pretreatment with the acids results in significant changes in the pyrolytic products. The residual P in the H3PO2-pretreated biomass apparently catalyzed the biomass deeper dehydration in pyrolysis compared to the other two mineral acids. TG analysis shows a shift of the temperature of maximum mass loss (Tmax) by more than 40 °C to lower temperature in the decomposition of the H3PO2-pretreated biomass from that of the untreated and the HCl- and H3PO4-pretreated biomass. Inspired by the striking differences in TG profiles of biomass pretreated by the three acids, thermal pyrolysis of pretreated biomass was carried out in a fixed bed reactor aimed at producing biochemicals at low temperatures (330 °C and 400 °C). The liquid products obtained from the fixed bed reactor show remarkably different major anhydrosugars as a result of pretreatment by the three acids. While phenolics dominate in the collected pyrolysis liquid from untreated biomass samples, biomass pretreated with all three acids results in substantially reduced phenolics in the bio-oils. The reduction in phenolic compounds in the bio-oil may be attributed to the reduction in mineral content in the feedstock. Consequently, the yields of anhydrosugars, mainly levoglucosan (LG) and levoglucosenone (LGO) are increased. LG yields of 20.9–28.5% from the cellulose content are obtained from HCl- and H3PO4-pretreated pine/poplar, with very low LGO yield (less than 1.7%). However, H3PO2-pretreated biomass is selective to produce LGO, especially at 330 °C. LGO yields of 7.4% and 6.7% are obtained from H3PO2-pretreated pine and poplar, respectively.

Effects of different nano fillers on the physical and mechanical properties of medium density fiberboards (MDF)

In this study, the physical and mechanical properties of medium density fiber boards (MDF) produced with urea formaldehyde adhesive reinforced with nano-boron nitride (BN) and nano-titanium dioxide (TiO2) were investigated. 0.5% and 1.5% nano-filled urea formaldehyde adhesives were used in the production of test samples. The density, thickness swelling, water uptake, internal bond strength, bending strength, modulus of elasticity in bending and SEM analysis of the boards prepered were determined. According to the laboratory tests conducted, there was no significant change in the density of the boards after nano filling. Physical properties such as water intake and thickness swelling were determined to decrease with the addition of nano particles. The mechanical properties of the boards increased with the addition of both nano-BN and TiO2. According to the a results of thermogravimetric analysis, it has been determined that the thermal stability of urea formaldehyde adhesive with TiO2 is increased and maximum mass loss temperatures are higher than the addition of nano-BN. The morphological structure of the urea formaldehyde adhesive was visualized with an electron microscope, and the nanoparticle dispersions were displayed and the particles were also analyzed by EDAX analysis. As a result, it has been determined that MDFs prepared with nanoparticle adhesives have improved physical, mechanical and thermal properties. Particularly, all samples with nano particles have been achieved the standards required in their mechanical properties. As a result, it can be sad that the adding nano-particles have positive effect on the physical and mechanical properties of the panels.

Design, synthesis and structure-property relationship of fluorenone-based derivatives for fluorescent OLEDs

Four fluorenone-based materials were designed, prepared and characterized for organic light emitting diodes. These derivatives possess relatively high thermal stability with the 5% mass loss temperatures in the range of 271–395 °C. The fluorenone-based materials showed oxidation bands in the range of 0.77–1.11 V. Ionization potential values of the films were found to be in the range from 5.11 to 5.41 eV. The differently substituted compounds were utilized as an emitters in organic light emitting diodes. Nevertheless, the doped devices based on 90 wt% 1,3-bis(N-carbazolyl)benzene as a host material have produced orange and red electroluminescence with CIEx,y of (0.52102, 0.43609) and (0.60724, 0.38766) with a low turn on voltage of 5.08 V, maximum external quantum efficiency of 2.54%, maximum brightness efficiency of 7509.14 cd/m −2 and maximum current and power efficiency of 15.73 cd/A −1 and 8.13 lm/W −1 respectively, that these results indicate that the 1,3-bis(N-carbazolyl)benzene host was matched and it is in the well agreement with emitters and select these series of compounds are an attractive approach for the extension of efficient fluorescence organic light emitting diodes.

Improved Weathering Performance of Poly(Lactic Acid) through Carbon Nanotubes Addition: Thermal, Microstructural, and Nanomechanical Analyses.

To understand the interrelationship between the microstructure and degradation behavior of poly(lactic acid) (PLA), single-walled carbon nanotubes (CNTs) were introduced into PLA as nucleating agents. The degradation behavior of PLA-CNT nanocomposites was examined under accelerated weathering conditions with exposure to UV light, heat, and moisture. The degradation mechanism proceeded via the Norrish type II mechanism of carbonyl polyester. Differential scanning calorimetry (DSC) studies showed an increase in glass transition temperature, melting temperature, and crystallinity as a result of the degradation. However, pure PLA showed higher degradation as evidenced by increased crystallinity, lower onset decomposition temperature, embrittlement, and a higher number of micro-voids which became broader and deeper during degradation. In the PLA-CNT nanocomposites, CNTs created a tortuous pathway which inhibits the penetration of water molecules deeper into the polymer matrix, making PLA thermally stable by increasing the initial temperature of mass loss. CNTs appear to retard PLA degradation by impeding mass transfer. Our study will facilitate designing environmentally friendly packaging materials that display greater resistance to degradation in the presence of moisture and UV light.

Analysis of radio activity and thermal decomposition of fly ash for application in light concrete production

The article deals with the environmental pollution from ash waste, the analysis of radioactivity and thermal decomposition of fly ash at thermal power plants used in the production of light concrete. It shows the research and analysis of fly ash of thermal power plants in Ekibastuz, Republic of Kazakhstan. In these studies, more attention is paid to the comparison of the radioactivity analysis of fly ash of a thermal power plant, for compliance with international standards and requirements for use in light concretes. There is the study of the thermal decomposition of fly ash. the process of thermal decomposition of fly ash of Ekibastuz TPP, The objective of the research is to determine radioactivity and thermal decomposition of fly ash at Ekibastuz TPP and establish the possibility of its potential use in the production of light concrete. Tthe process of decomposition of ash structure began at the temperature of 1100 ° C, with heat absorption effects (endothermic) at 240-380° C and heat release effect (exothermic) at 680° C, and a corresponding change in ash mass loss temperature of 1.2%.