Maximum Mass Loss Research Articles

Modification of Poly(Ethylene 2,5-Furandicarboxylate) with Poly(Ethylene glycol) for Biodegradable Copolyesters with Good Mechanical Properties and Spinnability.

Using 2,5-furandicarboxylic acid, ethylene glycol, and poly(ethylene glycol) as raw materials and ethylene glycol antimony as a catalyst, poly(ethylene furandicarboxylate) (PEF) and polyethylene glycol (PEG) copolymers (PEGFs) were synthesized by transesterification by changing the molecular weight of PEG (from 600 to 10,000 g/mol) and the PEG content (from 10 to 60 wt %). The thermal, hydrophilic, degradation, and spinnility characteristics of these copolymers were then investigated. Thermogravimetric analysis shows that PEGF is thermally stable at 62 °C, much lower than the temperature for PEF. The intrinsic viscosity of the obtained copolyester was between 0.67 and 0.99 dL/g, which is higher than the viscosity value of PEF. The contact angle experiment shows that the hydrophilicity of PEGFs is improved (the surface contact angle is reduced from 91.9 to 63.3°), which gives PEGFs a certain degradability, and the maximum mass loss can reach approximately 15%. Melt spinning experiments show that the PEGF polymer has poor spinnability, but the mechanical properties of the polymer monofilament are better.

Thermal behavior of woody residues in a reduced‐oxygen atmosphere using Macro‐thermogravimetric technique

AbstractIn the context of sustainable development, co‐gasification or co‐firing of biomass residues and coal is becoming a relevant solution to mitigate the negative impact of fossil fuels. For this reason, it is crucial to understand the characteristics, as well as the thermal behaviors of these residues, especially in a low‐oxygen condition that is often found in industrial processes. In this study, woody residues, namely bamboo and rubberwood chips that are abundantly available in Vietnam were characterized. Thermal degradation of these residues in 4 % oxygen was also conducted using a Macro‐thermogravimetric analyzer, from room temperature to 700 °C. The results showed that bamboo had a higher volatile matter and a higher hemicellulose content compared to rubberwood chips, hence is easier for ignition in a thermochemical conversion process. Regarding the thermal behaviors of these residues in a reduced‐oxygen condition, three stages could be clearly observed in the TGA‐DTG curves. Rubberwood chip had a higher ignition temperature and higher temperatures of maximum mass loss rate compared to bamboo chip. Results could contribute to the understanding of the thermal behaviors of these biomass feedstocks in order to improve the efficiency of co‐gasification or co‐firing processes.

Study on Pyrolysis Characteristics of Coal and Combustion Gas Release in Inert Environment

In this study, thermogravimetric analysis (TGA) coupled with Fourier transform infrared (FTIR) spectroscopy was used to heat the coal samples of six different coalification degrees from room temperature to 1000°C at 20°C·min−1 under nitrogen atmosphere. The influence of coal degree and pyrolysis temperature on the content of pyrolysis products of coal was analyzed by the TG/DTG curve. FTIR spectroscopy was used to obtain the IR spectra of generated gases and study their variation at different temperatures in the process of coal heating without oxygen, and the gas release during pyrolysis was discussed. The results showed that the pyrolysis reaction initiated at 400°C and ended at 800°C. The maximum mass loss occurred in the temperature range of 480 to 500°C. The values of maximum and minimum weight loss rates were 32.72 and 18.89%, respectively. The mass loss during the pyrolysis process corresponded well with the volatile matter contained in the sample. Permanent gas analysis and IR spectrum analysis indicated that when the temperature was 600°C, the peak value of methane (CH4) appeared at 3016 wave, indicating the generation of CH4 at this time. When the temperature reached 700°C, the peak area of 2360 wave increased, all coal samples began to release carbon dioxide (CO2), release rate of CH4 gas decreased, and yield of CO2 was maximized. At 800°C, all peaks of 3160 wave disappeared, indicating that there was no unreacted short-chain release at this temperature. At the same time, the pyrolysis reaction tended to remove the excess hydrogen-oxygen conjugates in the carbon structure and release them in the form of water vapor.

Erosion–corrosion behavior of SAF3207 hyper-duplex stainless steel

Polarization curves and mass losses of SAF3207 hyper-duplex stainless steel under various conditions were measured. The damaged surfaces after erosion–corrosion tests were characterized by scanning electron microscopy. The results showed that an increase in flow velocity could enhance the electrochemical corrosion and consequently decrease the passivation properties of the steel. The erosion–corrosion damage of the samples increased substantially when the flow velocity exceeded the critical value of 4 m·s−1. The mass loss rate increased as the sand content increased, reaching a maximum at 7wt% sand content, corresponding to the most severe electrochemical corrosion damage. When the sand content was increased further, however, the mass loss rate decreased and then tended stable. The mass loss was divided into incubation, sustained, and stationary periods, with a maximum mass loss rate of 12.97 g·h−1·m−2 after an erosion period of 2.5 h. The erosion–corrosion mechanism was investigated in detail.

Spontaneous Combustion Characteristics of Coal by Using the Simultaneous Thermal analysis–Fourier Transform Infrared Spectroscopy Technique

ABSTRACT Understanding the development process of coal oxidation reactions can aid in preventing coal spontaneous combustion. Oxidation heating experiments on anthracite, bituminous coal, and lignite at different heating rates were carried out using simultaneous thermal analysis–Fourier transform infrared spectroscopy (STA–FTIR). The experimental results show that combining TG, DSC, CO, CO2 and H2O curves in the spontaneous combustion process of coal, the maximum acceleration point Ta and maximum mass loss rate T4 are important for judging the severity of the coal spontaneous combustion hazard. Meanwhile, Ta is more accurate as the ignition temperature point than the ignition temperature T3. As the coal’s rank and heating rate increases, the characteristic temperatures moved to higher temperature. The higher degree of metamorphism has a higher ignition activation energy. Additionally, the reaction models for ignition activation energy between anthracite and bituminous coal changed from three-way transport to random nucleation and nuclei growth with the increase of metamorphic rank, but were not affected by the heating rate.

Assessment of biomass energy potential for SRC willow woodchips in a pilot scale bubbling fluidized bed gasifier

The current study investigates the short rotation coppice (SRC) gasification in a bubbling fluidized bed gasifier (BFBG) with air as gasifying medium. The thermochemical processes during combustion were studied to get better control over the air gasification and to improve its effectiveness. The combustion process of SRC was studied by different thermo-analytical techniques. The thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were performed to examine the thermal degradation and heat flow rates. The product gas composition (CO, CO2, CH4 and H2) produced during gasification was analyzed systematically by using an online gas analyzer and an offline GC analyzer. The influence of different equivalence ratios on product gas composition and temperature profile was investigated during SRC gasification. TG/DTG results showed degradation occur in four stages; drying, devolatilization, char combustion and ash formation. Maximum mass loss ~70% was observed in devolatilization stage and two sharp peaks at 315–500 °C in TG/DSC curves indicate the exothermic reactions. The temperature of gasifier was increased in the range of 650–850 °C along with the height of the reactor with increasing equivalent ratio (ER) from 0.25 to 0.32. The experimental results showed that with an increment in ER from 0.25 to 0.32, the average gas composition of H2, CO, CH4 decreased in the range of 9–6%, 16–12%, 4–3% and CO2 concentration increased from 17 to 19% respectively. The gasifier performance parameters showed a maximum high heating value (HHV) of 4.70 MJ/m3, Low heating value (LHV) of 4.37 MJ/m3 and cold gas efficiency (CGE) of 49.63% at 0.25 ER. The ER displayed direct effect on carbon conversion efficiency (CCE) of 95.76% at 0.32 ER and tar yield reduced from 16.78 to 7.24 g/m3 with increasing ER from 0.25 to 0.32. All parametric results confirmed the reliability of the gasification process and showed a positive impact of ER on CCE and tar yield.

Combustion behavior of large size coal over a wide range of heating rates in a concentrating photothermal reactor

Combustion behaviors of large size coal pellets were studied in a novel room temperature chamber type concentrating photothermal apparatus. 4 heating rates of 4.0 °C/s, 15.1 °C/s, 52.4 °C/s and 69.4 °C/s were realized by adjusting the voltage-up rates of the heating lamps. The temperature, image, gas emission, and mass loss were synchronously detected and the reliabilities of data were strictly verified. Coal pellets presented “heterogeneous” ignition mechanism at slow (4.0 °C/s) heating rate, “joint homo-heterogeneous” at moderate (15.1 °C/s) heating rate, and “homogeneous” at sub-fast (52.4 °C/s) and fast (69.4 °C/s) heating rates. High concentrations of CO and CH4 were evident at all heating rates. The increase of heating rate accelerated all gas generation rates and leaded to the gas yield reduction of CO but rising of CO2. Kinetics studies of the reactions around the maximum mass loss rate were carried out ultimately. 1-dimensional diffusion mechanism model (D1) showed best correlation coefficients with the reactions at slow, moderate and sub-fast heating rates and the apparent activation energies slightly decreased from 84.45 and 66.18 to 62.28 kJ/mol. The fitting curve of reactions at fast heating rate was two-stage-style and correlated best to the 3-dimensional diffusion mechanism model based on Jander equation (D3) with activation energies of 33.74 and 11.54 kJ/mol.

Effect of K2CO3 as an Additive Agent on the Carbothermic Reduction Process of Silicon Production

The effect of K2CO3 as an additive agent in the carbothermic reduction process of silicon production is investigated in this study. Using a thermogravimetric analyzer (TGA) in argon atmosphere, different proportions of petroleum coke (PC) and pomelo peel (PP) are used as the carbonaceous reducing agent. Findings show that the additive displays catalytic activities for reductant composition of PC and PP in solid state under high temperature. The maximum mass loss rate of samples with additive is found to increase by 13.7% in the same conditions, compared to samples without the additive. In addition, a homogenous model (HM) is studied as a kinetic model using the Coats-Redfern method to observe and determine the kinetic parameters of all samples. High correlation coefficient values for the pyrolysis stages (R2 > 0.99) and the carbothermic reduction stage of silicon dioxide (R2 > 0.98) are obtained for all samples, illustrating that the kinetic model is applicable to this reaction process. According to findings in this study, the additive K2CO3 is determined to positively impact reaction activity, speeding up the rate of pyrolytic reaction and the carbothermic reduction of silica.

Impact Performance of Helmholtz Self-Excited Oscillation Waterjets Used for Underground Mining

Pulsed waterjets are widely used in exploitation of fossil fuels for their high efficiency. With the aim to further clarify the impact performance of Helmholtz self-excited oscillation waterjets (HSEOW), numerical and experimental studies were conducted. The morphological characteristics of the erosion surfaces between conical and HSEOW nozzles were compared and the cavitation evolution was obtained. Results show that the cavitation damage caused by the HSEOW nozzle on the specimen was mainly caused by the jet cavitation cloud under submerged conditions. The cavitation effect produced by the HSEOW nozzle had a much greater destructive effect than that of a conical nozzle. The mass loss caused by HSEOW nozzles increased first with the increase of standoff distance, then decreased rapidly after reaching the maximum value. Moreover, the density of holes and the damage intensity weakened with the increase of radial distance. A dimensionless cavity length of 2 and a dimensionless cavity diameter of 8 was the optimal structure that led to maximum mass loss. These results provide a further understanding of cavitation mechanism which leads to the impact performance of pulsed water jets and optimal working parameters in the field of energy exploitation.

Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N‐alkylpyrrole Derivatives

To expand the library of pyrrole‐containing flavor precursors, two new flavor precursors—methyl N‐benzyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NBMF) and methyl N‐butyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG‐DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2‐methylpyrrole, 1‐methylpyrrole‐2‐carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.

Effect of moisture content and compaction on the corrosion of mild steel buried in clay soils

ABSTRACTThe corrosion of steels in clay soils is of interest for buried steel infrastructure. To obtain better information about the early corrosion effects, mild steel coupons were exposed for 3, 6 and 13 months in finely graded clay soil at different moisture contents and with different degrees of compression to simulate compaction. It was found that the maximum corrosion mass loss and pit depths occurred at a soil moisture content of 17–18 wt-% for all exposures and levels of compaction, corresponding to around 0.65 degree of saturation. These values are broadly consistent with earlier findings for non-clay soils. For exposures of 3 months corrosion was predominantly localised but subsequently became more uniform. This was shown to be consistent with good compaction of the soil against the steel surface. Poorly compacted lumpy clays, however, showed larger areas of localised corrosion and relatively greater corrosion mass loss and deeper pitting.

Nanosized carbon black as synergist in PP/POE-MA/IFR system for simultaneously improving thermal, electrical and mechanical properties

Nanosized carbon black (CB) was introduced into polypropylene/maleic anhydride-grafted polyolefin elastomer/intumescent flame retardant (PP/POE-MA/IFR) system to investigate the effect of nanofiller as synergist on thermal, electrical and mechanical properties of polymer composites. With 5 mass% CB into PP/POE-MA/IFR system (POFC5), the Tmax (corresponded to the temperature at the maximum mass loss rate) under air was increased by 122.4 °C; its limited oxygen index was as high as 31.4%; its vertical burning rating (UL-94) reached V0, and the peak value of heat release rate was decreased to only 19% of neat PP in cone calorimeter testing. Moreover, PP composites exhibited good electrical conductivity with more than 1.6 mass% CB, which is a low loading level to reach the critical percolation concentration. In addition, a good balance on stiffness and toughness of PP composites was achieved; especially, Young’s moduli and impact strength of POFC5 were increased to 1.26 and 2.5 times in comparison with that of neat PP, respectively. These results indicated that CB was an effective synergist in multi-component PP composites to simultaneously improve thermal, electrical and mechanical properties.

Effects of ternary potassium containing intumescent flame retardant coating on the combustion and thermal degradation properties of reconstituted tobacco sheet

Reconstituted tobacco sheet (RTS) was first modified by ternary intumescent flame retardant (IFR) coating, composed of ammonium polyphosphate (APP), chitosan (CS), and potassium citrate (PC) by spraying deposition sequentially. The effects of composite coating on the combustion behavior and thermal degradation of RTS were studied by micro-scale combustion calorimetry (MCC), cone calorimetry (CC) and thermogravimetric analysis coupled by Fourier transform infrared spectrometer (TG-FTIR). MCC analysis indicated that the ternary coating presented the best flame retardancy with the proportion of APP, CS and PC at 1:1:5 (wt %). TG-FTIR results showed that APP-CS-PC coating reduced the maximum mass loss rate and the release of harmful gaseous products at the stage of char decomposition and PC promoted the formation of a potassium carbon complex, which was also supported by carbonyl compounds analysis. Moreover, for APP-CS-PC-RTS cigarette, the formaldehyde yield in mainstream smoke and the highest temperature of burning cone decreased by 67.28% and 100.1℃, respectively.

Thermal Decomposition Kinetics of Flame Retardant Polybutylene Terephthalate Matrix Composites

The thermal decomposition kinetics of polybutylene terephthalate (PBT) and flame-retardant PBT (FR-PBT) were investigated by thermogravimetric analysis at various heating rates. The kinetic parameters were determined by using Kissinger, Flynn-Wall-Ozawa and Friedman methods. The y (α) and z (α) master plots were used to identify the thermal decomposition model. The results show that the rate of residual carbon of FR-PBT is higher than that of PBT and the maximum mass loss rate of FR-PBT is lower than that of PBT. The values of activation energy of PBT (208.71 kJ/mol) and FR-PBT (244.78 kJ/mol) calculated by Kissinger method were higher than those of PBT (PBT: 195.54 kJ/mol) and FR-PBT (FR-PBT: 196.00 kJ/mol) calculated by Flynn-Wall-Ozawa method and those of PBT and FR-PBT (PBT: 199.10 kJ/mol, FR-PBT: 206.03 kJ/mol) calculated by Friedman methods. There is a common thing that the values of activation energy of FR-PBT are higher than that of PBT in different methods. The thermal decomposition reaction models of the PBT and FR-PBT can be described by Avarami-Erofeyev model (A1).

Study on the effect of ethanol content on the fire risk of nitrocellulose

Obtaining the burning properties of nitrocellulose with different ethanol contents is necessary to reduce the possibility of nitrocellulose accidents in the process of handing, storage and usage. In this study, the effect of humectant content on the burning properties of NC was tested by the ISO 5660 Cone Calorimeter Test. It was noted that the amount of the ethanol content had little effect on the ignition time of nitrocellulose mixture. Both the maximum mass loss rate and the average mass loss rate of the sample decreased with an increasing ethanol content and gradually closed to fixed values. Also, it was concluded that the peak heat release rate of the sample was mainly contributed by the nitrocellulose component.

Corroded RC Beams at Service Load before and after Patch Repair and Strengthening with NSM CFRP Strips

This paper presents the experimental results of the structural behavior of four reinforced concrete beams with corroded steel reinforcement at service loads. One beam was non-corroded, one beam was corroded under an accelerated electrochemical technique to a small corrosion level (for one corrosion cycle), while two beams were corroded under the same conditions of an accelerated electrochemical technique and then subjected to vertical service loads that corresponded to 60% and 75% of the yield load of the non-corroded beam respectively for three corrosion cycles (with maximum mass loss around 25% for the first and 31% for the latter). Longitudinal cracks due to corrosion and flexural cracks due to loading were thoroughly recorded at the end of each cycle. The beam under the 75% service load had higher deflection increase for heavier corrosion. After the three successive serviceability load tests, the cracked concrete cover was removed and the steel rebars were treated. The cement-based repair mortar and two NSM FRP laminates were applied to both beams and were tested to failure. Despite the heavy corrosion, the patch repair and NSM strengthening enhanced the load-bearing capacity of the beams when compared with the non-corroded beam. All 10 tests are thoroughly discussed.

On the removal behavior of aluminum paste for silicon solar cell

The removal behavior of the aluminum paste was investigated using thermogravimetric analyzer, and it was found that the mass loss curve could be divided into two main stages including low-temperature and high-temperature stages and a complex transition between them. The pre-exponential factors of the two main stages were calculated by Kissinger method. And the activation energies were determined using different methods named as Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sinose (KAS) and Kissinger. The dependence of the activation energy on the conversion has been analyzed in detail. The activation energy of the low-temperature stage keeps approximately constant, and the average value is 38.74 kJ mol−1 of FWO method and 33.86 kJ mol−1 of KAS method. According to KAS method, the activation energy for the high-temperature stage decreases from 157.03 to 94.65 kJ mol−1 with the temperature increasing from 596 to 675 K. The variation range of the activation energies indicates the existence of a complicated reaction mechanism during the high-temperature stage. Though high removal rate during the low-temperature stage is beneficial to reducing the processing time of silicon solar cells, the heating rate should be controlled when the temperature is close to the value resulting in the maximum mass loss rate to avoid causing defects in the aluminum back electrode.

Chemical and nanostructural characteristics of the particulate matter produced by renewable diesel fuel in an automotive diesel engine

Renewable diesel (RD), a paraffinic fuel produced by the hydrotreating of palm oil, was used neat and blended at 10% and 30% (by volume) with ultra-low sulfur diesel (ULSD) to generate particles in an automotive diesel engine operating at two engine speeds (1890 and 2410 min−1) under the same engine load (95 Nm). Particulate matter was characterized using thermogravimetric analysis (TGA), Raman spectroscopy, X-Ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), and X-Ray photoelectron spectroscopy (XPS). Oxidation profiles showed that diesel soot is slightly more reactive than the soot produced by RD and its blends, independently of the engine speed (the maximum mass loss rate temperature –MLRTmax– was 6.6 °C lower for ULSD than neat RD). This behavior was in agreement with the active surface area (ASA) of the particles, which varied between 10.8 m2/g for RD to 13.9 m2/g for ULSD at the same engine speed. Soot nanostructure (ratio of Raman peaks) and interlayer distance show a slightly higher degree of order of the particles when RD was added into diesel fuel. The mean primary particle diameter of neat RD soot was around 26 nm and fractal dimension of the agglomerates was around 1.66, which were both lower in comparison with ULSD (32 nm and 1.97, respectively). Fringe analysis applied to HRTEM micrographs revealed no clear trend in the fringe length and tortuosity among soot samples. Finally, it was found that, independently of the fuel tested, all particle samples gathered at 2410 min−1 were slightly more reactive and smaller than those collected at 1890 min−1. From this engine configuration and specific experimental setting, it can be expected that the use of RD blends would not markedly affect the performance of aftertreatment devices like diesel particulate filters.

Hydrolyzable Additive-Based Silicone Elastomers: A New Approach for Antifouling Coatings.

Fouling Release Coatings are marine antifouling coatings based on silicone elastomers. Contrary to commonly used biocide-based antifouling coatings, they do not release biocides into the marine environment, however, they suffer from poor antifouling efficacy during idle periods. To improve their antifouling performances in static conditions, various amounts of hydrolyzable polymers were incorporated within a silicone matrix. These hydrolyzable polymers were chosen for the well-known hydrolytic degradation mechanism of their main chain, e.g. poly(ε-caprolactone) (PCL), or of their ester pending groups, e.g. poly(bis(trimethylsilyloxy)methylsilyl methacrylate) (PMATM2). The degradation kinetics of such hydrolyzable silicone coatings were assessed by mass loss measurements during immersion in deionized water. Coatings containing PMATM2 exhibited a maximum mass loss after 12 weeks, whereas PCL-based coatings showed no significant mass loss after 24 weeks. Dynamic contact angle measurements revealed the modifications of the coatings surface chemistry with an amphiphilic behavior after water exposure. The attachment of macrofoulers on these coatings were evaluated by field tests in the Mediterranean Sea, demonstrating the short or long-term antifouling effect of these hydrolyzable polymers embedded in the silicone matrix. The settlement of A. amphitrite barnacles on the different coatings indicated inhospitable behaviors towards larval barnacles for coatings with at least 15 wt % of additives.

Thermal conversion behaviors and products of spent mushroom substrate in CO2 and N2 atmospheres: Kinetic, thermodynamic, TG and Py-GC/MS analyses

This study aims at characterizing pyrolysis/gasification behaviors and products of spent mushroom substrate (SMS) in the CO2 and N2 atmospheres. The major decomposition stages occurred between 200 and 600 °C with the mass losses of 60.4 and 61.5% at 20 °C/min in the CO2 and N2 atmospheres, respectively. The maximum mass loss rate grew with the increased heating rate, while DTG curves shifted toward a higher temperature. Volatiles were released easier in the N2 than CO2 atmosphere with a higher comprehensive devolatilization index and decomposition rate. At above 750 °C, the char gasification in the CO2 atmosphere resulted in a significant mass loss as well as a less char yield. Average activation energies by the Flynn-Wall-Ozawa method were estimated at 212 and 214 kJ/mol in the CO2 and N2 atmospheres, respectively. The higher thermodynamic parameters in the N2 than CO2 atmosphere indicated the higher reactivity of the pyrolysis in the N2 atmosphere. The reaction mechanisms of the volatiles decomposition were best described by g(α) = (1-α)−1-1 (R2 model) in the range of 200–370 °C in both atmospheres. The major pyrolysis products at 800 °C were identified using Py-GC/MS and composed mostly of aromatic compounds such as toluene and x-methyl-naphthalenes.