Exothermic Onset Temperature Research Articles

Binder-dependent electrochemical properties of high entropy oxide anodes for lithium-ion batteries

High entropy oxide (HEO) materials have recently emerged as promising anodes for lithium-ion batteries (LIBs). In this study, we conduct the first comparative analysis to investigate the influence of various electrode binders on electrochemical properties of (CrMnFeNiCu)3O4 HEO anodes. The organic-solvent-soluble polyvinylidene fluoride and water-soluble polyvinyl formamide, sodium carboxymethyl cellulose, sodium alginate, and sodium polyacrylate (NaPAA) binders are examined. Notably, the NaPAA binder leads to a significant enhancement in the HEO performance. The NaPAA coating on (CrMnFeNiCu)3O4 effectively improves the electrode charge-discharge Coulombic efficiency and mitigates the electrode deterioration. Binder adhesion strength and stability toward electrolyte are assessed. The charge-transfer resistance and apparent Li+ diffusion of the HEO electrodes with various binders, accompanied by the post-cycling analyses, are examined. By employing the NaPAA binder, exceptional electrode capacities of 800 and 495 mAh g–1 are attained at charge-discharge rates of 50 and 2000 mA g–1, respectively, without noticeable capacity degradation after 300 cycles. The thermal reactivity of the lithiated electrodes is investigated using differential scanning calorimetry, and the impact of binders on the electrode exothermic onset temperature and total heat released is studied. Our findings provide valuable insights for enhancing the performance and safety of HEO anodes for LIBs.

Oxidation properties and thermal hazard of pinane

Although pinane has a wide range of uses, there are no reports on the safety of pinane oxidation. The thermal oxidation properties of pinane were investigated through MCPVT. The primary oxidation products of pinane were separated and structurally characterised, and its decomposition properties were assessed by MCPVT and DSC. The results showed that pinane had an initial oxygen uptake temperature of 123.5 °C and exploded when the temperature rose to 132.7 °C. Pinane autoxidised at 110 °C for 9 h formed a high level of peroxide (81.18 mmol/kg) with an activation energy of 138.77 kJ/mol. The oxidation of pinane occurs mainly at the tertiary carbon atom attached to the methyl group, and the main peroxide produced is pinane hydroperoxide (PHP). PHP has an exothermic onset temperature (Tonset), a heat of decomposition (QDSC) and an activation energy of decomposition of 114.6 °C, 1878.0 J/g and 109.4 kJ/mol respectively, which should classify it as a hazardous substance. PHP has a lower activation energy than pinane and is the determining factor for the safety of the pinane oxidation reaction. The products of thermal runaway of pinane are relatively complex and consist mainly of 1-(2, 2-dimethyl-3-ethylcyclobutyl) ethanone, nopinone, 2, 3-pinanediol and pinonic acid.

Thermal stability of levopimaric acid and its oxidation products

Biofuels are renewable alternatives to fossil fuels. Levopimaric acid‒base biofuels have attracted increasing attention. However, their stability remains a critical issue in practice. Thus, there is a strong impetus to evaluate the thermal stability of levopimaric acid. Through thermogravimetry (TG) and a custom-designed mini closed pressure vessel test (MCPVT) operating under isothermal and stepped temperature conditions, we investigated thermal oxidation characteristics of levopimaric acid under oxygen atmosphere. Thin-layer chromatography (TLC) and iodimetry were used to measure the hydrogen peroxides generated by levopimaric acid oxidation. A high pressure differential scanning calorimeter (HPDSC) was used to assess hydroperoxide thermal decomposition characteristics. Gas chromatography-mass spectrometry (GC-MS) was used to characterize the oxidation products. The thermal decomposition kinetics of levopimaric acid were thus elucidated, and a high peroxide value was detected in the levopimaric acid. The decomposition heat (QDSC) and exothermic onset temperature (Tonset) of hydroperoxides were 338.75 J g−1 and 375.37 K, respectively. Finally, levopimaric acid underwent a second-stage oxidation process at its melt point (423.15 K), resulting in complex oxidation products. Thermal oxidation of levopimaric acid could yield potential thermal hazards, indicating that antioxidants must be added during levopimaric acid application to protect against such hazardous effects.

Cell-to-cell variability in Li-ion battery thermal runaway: Experimental testing, statistical analysis, and kinetic modeling

As one of the most promising energy storage mediums, Lithium-ion batteries (LIBs) have attracted extensive research interest. A major challenge associated with LIB application is thermal runaway, which can be triggered under abused conditions and impose direct threats to lives and properties. Here, we select Li-ion batteries with lithium cobalt oxide cathode and graphite anode (18650, Samsung), with relatively simple chemistry, to revisit thermal runaway. The experiment is conducted using an accelerating rate calorimeter (EV+ ARC, Thermal Hazard Technology) following the heat-wait-seek strategy, and is repeated for 9 similar new cells with 100 % state of charge (SOC). Key features such as onset temperature of self-heating, the onset temperature of thermal runaway, maximum heat release rate, thermal runaway delay time, and maximum temperature are measured experimentally. Although the cells are all brand new and have been initiated similarly, obvious cell-to-cell variability has been observed in the measured exothermic onset temperature, delay time, and mass losses. It is also shown that the widely used four-step thermal runway model cannot quantitatively capture the activation energy from the heat release rate. To improve the kinetic modeling and accommodate the cell-to-cell variability, statistical analysis is conducted to process the experimental results. Mean and standard deviation of the frequency factor and activation energy has been acquired to determine the lower and upper bound of the kinetic modeling using a one-step global chemistry. The measured and simulated thermal runaway delay time has reached a reasonable agreement, with the uncertainty of the kinetic model considered. The role of reactant consumption during the heating process is also discussed. The identified cell-to-cell variability should not only be considered for cell-level safety evaluation and modeling, but also in the thermal runaway propagation of battery modules and packs.

Cell-to-Cell Variation in Thermal Runaway Behavior

As one of the most promising energy storage mediums, Lithium-ion batteries (LIBs) have attracted extensive research interest. A major challenge associated with LIB application is thermal runaway, which can be triggered during overheating, overcharging, collision, and other abused conditions, leading to a direct threat to lives and properties. Here, we select Li-ion batteries with lithium cobalt oxide cathode and graphite anode (18650, Samsung), which are relatively simple and extensively investigated, to revisit thermal runaway. The experiment is conducted using an accelerating rate calorimeter (EV+ ARC, Thermal Hazard Technology) following the standard heat-wait-seek strategy, and is repeated for 9 similar new cells with 100% state of charge (SOC). Key features such as onset temperature of self-heating, the onset temperature of thermal runaway, maximum heat release rate, thermal runawaydelay time, and maximum temperature are measured experimentally. Although the cells are all brand new and have been initiated similarly, obvious cell-to-cell variability has been observed during thermal runaway. Major differences exhibit in the measured exothermic onset temperature, delay time, and mass losses; however, each cell nevertheless shows highly consistent activation energy processed from the heat release rate. Additionally, thermal runaway models are established in COMSOL to simulate the experimental conditions, with and without the effect of reactant consumption during the heating stage. It is shown that the widely used four-step thermal runway model cannot quantitatively capture the activation energy from the heat release rate. To improve the kinetic modeling and accommodate the cell-to-cell variability, statistical analysis is conducted to process the experimental results. Meanand standard deviation of the frequency factor and activation energy has been acquired to determine the lower and upper bound of the kinetic modeling using a one-step global chemistry. The measured and simulated thermal runaway delay time has reached a reasonable agreement, with the uncertainty of the kinetic model considered. The identified cell-to-cell variability is most likely due to manufacturing inconsistencies, which should not only be considered for cell-level safety evaluation but also the design and evaluation of battery modules and packs.

Thermal stability evaluation of tert-butyl peroxybenzoate mixed with impurities

In this article, the thermal stability of tert-butyl perbenzoate (TBPB) mixed with different concentrations of toluene and p-tert-butylcatechol (TBC) was investigated. The exothermic onset temperature (T 0), the heat of decomposition (ΔH), and the adiabatic temperature rise (ΔTad ) of the samples were obtained by differential scanning calorimetry (DSC) and Phi-TEC II adiabatic calorimetry. The apparent activation energy (Ea ) and the maximum reaction rate arrival time under adiabatic conditions were obtained by adiabatic kinetic calculations for 8 h (TD8 ) and 24 h (TD24 ). Based on Semenov’s theory, the self-accelerated decomposition temperature was calculated as a support for safe storage and transport. The results of DSC and Phi-TEC II showed that toluene was effective in reducing the thermal hazard during the decomposition of TBPB. The addition of TBC caused side reactions. The moderate addition of toluene and TBC improves the thermal stability of TBPB and can improve the safety of TBPB in industrial applications.

Thermal risk evaluation of concentrated electrolytes for Li-ion batteries

Concentrated electrolytes have been attracting increasing attention due to their unique properties. However, despite the concern about their thermal stability, few research has been done on their exothermic behaviors, especially with the coexistence of electrodes. Herein, we report the results of detailed investigation into the thermal properties of LiBF 4 , LiPF 6 , LiTFSI, and LiFSI/carbonate concentrated solutions and their thermal behaviors with the coexistence of fully lithiated graphite. Concentrated LiBF 4 solutions showed no practical application possibilities because they were unstable on C 6 Li. Increasing the salt concentration decreased the thermal stability of LiPF 6 /PC solutions with the coexistence of C 6 Li. The organic salt dominated the thermal behavior of the solution when mixed with C 6 Li. A drastic exothermic reaction happened at 210–220 °C when C 6 Li was mixed with LiFSI solutions, indicating a very high thermal risk of LiFSI carbonate solutions as LIB electrolytes. In contrast, LiTFSI solutions showed much milder reactions with C 6 Li. On the other hand, because of the different LiF content in SEI, the exothermic onset temperature of the C 6 Li mixture with the concentrated solution increased in the order of LiFSI > LiTFSI > LiPF 6 . Comprehensively, concentrated LiTFSI electrolytes should be a good choice for LIB from the standpoint of battery safety. • TG-DSC analysis on Li salt-carbonate solutions with/without C 6 Li were performed. • Concentrated LiBF 4 and LiPF 6 electrolytes had poor temperature tolerance on C 6 Li. • LiFSI solutions could protect C 6 Li until 150 °C and then drastically reacted. • LiTFSI/DMC solutions showed excellent thermal stability up to 400 °C. • Highly concentrated LiTFSI electrolytes should be a good choice for safer LIB.

Oxidation characteristics and explosion risk of 2, 5-dimethylfuran at low temperature

The thermal oxidation reaction of 2,5-dimethylfuran (DMF) was investigated using a custom-designed mini closed pressure vessel test (MCPVT) and traced by 1H nuclear magnetic resonance(1H NMR). The oxidation behavior was monitored by-via temperature–time (T-t) and pressure–time (p-t) plots of MCPVT recording. Oxidation products were determined via gas chromatography-mass spectrometry (GC–MS), and the generated peroxide was examined by iodimetry and thin-layer chromatography (TLC), with the thermal decomposition hazard evaluation by differential scanning calorimeter (DSC) and MCPVT. Results show that the DMF oxidation reaction proceeded through initial oxygen absorption at 39.3 °C, followed by an exothermic self-accelerating oxidation at 84.5 °C. DMF could form high level peroxide in auto-oxidation; the decomposition of peroxides would lead to the radical oxidation that the generated ·OH radical mainly attacks on the position 2/5 of DMF with subsequent addition of O2 initiating ring-opening reaction, in which DMF was firstly converted to cis-3-hexene-2,5-dione, and then produced the trans-3-hexene-2,5-dione with strong photoisomerism. DMF oxidation showed a high level of residue formation, and those solid products contained considerable amount of peroxides with a high thermal hazard; its exothermic onset temperature (T0) and decomposition heat (QDSC) of 58.8 °C and 1982.3 J∙g−1, and the decomposition maximum temperature rising rate (dT/dt)max and maximum of pressure rising rate (dp/dt)max was 9.98 °C∙s−1 and 291 kPa∙s−1, respectively. Thermal decomposition of those peroxide products could give rise to thermal runaway of DMF oxidation, and further transformed into a detonation possibly.

Enhanced high-temperature performance and thermal stability of lithium-rich cathode via combining full concentration gradient design with surface spinel modification

Abstract Lithium-rich layered oxides (LLOs) are considered as the most promising candidate for the cathode of high energy density lithium-ion batteries. However, the poor cycle stability especially under high temperature is hindering its practical applications. Herein, a full concentration gradient LLO with spinel modification is designed and prepared. This synergistic strategy not only makes full use of high Ni content that improving the discharge voltage but also mitigates the detrimental influence of surface residual alkalis. The surface spinel modified cathode exhibits a higher initial coulombic efficiency of 87.52% with enhanced cycle stability at 55 °C (191.5mAh/g after 200 cycles at 1C), the average discharge voltage drop is also alleviated to 3.17 mV per cycle (at 55 °C). Furthermore, it also shows enhanced thermal stability, in which the exothermic onset temperature rises from 265.380 to 295.221 °C, and the thermal release decreases from 211.525 to 181.181 J/g. This work proposes an integrated strategy to enhance the comprehensive performance of LLOs, thus shed a light on the way for its practical application.

Comparative analysis of exothermic behaviour of fresh and weathered coal during low-temperature oxidation

Spontaneous combustion of weathered coal is the main hazard in coal-rich countries which needs to be addressed. The exothermic behaviour of weathered coal on low-temperature oxidation was investigated in fresh and weathered coal during spontaneous combustion. The variation law of thermal diffusivity, specific heat, and thermal conductivity of weathered coal on spontaneous combustion oxidation was analysed using the laser flash technique. Weathered coal thermal conduction characteristics were enhanced compared with fresh coal. On the basis of differential scanning calorimetry results, the characteristics of the thermal effect during the low-temperature oxidation of weathered coal were studied by conducting C80 micro thermal. The exothermic onset temperature and total thermal energy of weathered coal were lower than those of fresh coal, as the thermal release showed distinct stage characteristics. The exothermic characteristics of various reaction stages were determined. The influence of the heating rate during the low-temperature reaction of weathered coal was evaluated. The heat flow obtained using the iso-conversion method indicated that the apparent activation energy of weathered coal varied with the reaction process. The results can provide a basis for the prevention and control of spontaneous combustion of weathered coal.

DFT and experimental study on adsorption of dyes on activated carbon prepared from apple leaves

This work reports utilization of apple leaves as a source of activated carbon. Activated carbon from apple leaves is prepared by two different methods, thermal activation where AC1 is obtained and chemical activation using H3PO4 and ZnCl2 where AC2 and AC3 are obtained, respectively. XRD analysis revealed that all types of prepared ACs have a semi-crystalline nature with a mean crystallite size of 13, 21.02, and 39.47 nm for AC1, AC2, and AC3, respectively. To identify the most suitable desorption temperature, the exothermic behavior was discovered for the three types of ACs by DSC. The exothermic onset temperatures are 340 °C, 200 °C, 400 °C, or AC1, AC2, and AC3, respectively. The point of zero charge for the three types of ACs is 8.6, 7.3, and 2.5 for AC1, AC2, and AC3, respectively. The BET surface area analysis data demonstrated that mesoporous structure was developed in AC1 and AC2, while a microporous structure was developed in AC3. Quantum chemical calculations for ACs is carried out using Density Functional Theory (DFT). Application of the prepared ACs in adsorption of basic dye C.I. base blue 47 is studied. The maximum removal efficiency was 65.1%, 96% and 99% for AC1, AC2, and AC3, respectively under the influence of different operating aspects. Adsorption data are modeled by Langmuir, Freundlich, and Temkin isotherms. The data revealed that adsorption of basic dye C.I. base blue 47 on AC1 follows Langmuir isotherm and adsorption on AC2 and AC3 follows Freundlich isotherm.

Thermal safety assessment for solid organic peroxides

The thermal hazards of dicumyl peroxide (DCP) and benzoyl peroxide (BPO), self-reactive chemicals are identified and characterized using high-pressuredifferential scanning calorimeter, and simultaneous thermogravimetric analyzer, a C80 micro-calorimeter is used. The apparent exothermic onset temperature of DCP is found to be between the range of 112–122 °C for different heating rates in DSC tests. There are two coupled peaks of BPO around 105 °C at both the heating rates of 4.0 and 8.0 °C/min while no endothermic peak showed at lower heating rates. Furthermore, another endothermic peak appears immediately after the exothermic peak at about 211 °C of DCP under high-pressure conditions. For BPO, the endothermic peak before the exothermic peak disappears as the pressure increases to 1.0 and 1.5 MPa. The average values of apparent activation energy calculated by Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods during the conversion rate between 15 and 75% of DCP are 80.69 and 74.05 kJ/mol, and that of BPO are 119.96 and 112.93 kJ/mol, respectively. According to the isothermal tests, the thermal decomposition of DCP behaviors is an n-th order reaction while BPO conforms to the laws of autocatalytic reaction.

Thermal runaway induced by dynamic overcharge of lithium-ion batteries under different environmental conditions

The present study aims to investigate thermal runaway induced by dynamic overcharge of lithium-ion batteries (LIBs) with Lix(Ni0.3Co0.3Mn0.2)O2 cathode under different environmental conditions. LIBs were overcharged with different charging ratios to thermal runaway in the ambient and adiabatic environment. The battery is more susceptible to thermal runaway in an adiabatic environment. The time $$T_{0}$$ (apparent exothermic onset temperature) of the battery in an adiabatic environment was 160 s, 260 s, and 500 s shorter than that in the ambient environment. When $$T_{0}$$ is detected, batteries need to be cooled within 14 min to prevent thermal runaway. Due to over-potential, the battery voltage will drop in the next stage after reaching the highest point. The inflection point voltage of the battery during overcharging is due to the deposition of metallic lithium in the anode graphite, which causes a significant potential shift of the anode. In the overcharging process, when the battery reaches the inflection point voltage, it must be terminated within 5 min and take measures to prevent thermal runaway. These results can render supports for understanding the overcharge mechanism and battery management system.

Thermal decomposition characteristics of diethyl azodicarboxylate dissolved in three ionic liquids as solvents

Azo-peroxyester, a multifunctional elemental energetic material, has low efficiency when indirectly acting on the target product in a reaction. If azo-peroxyester is dissolved in an appropriate solvent, the yield is greatly improved. With the aim of perfecting the safety of diethyl azodicarboxylate (DEAD) in industrial process applications, this study evaluated the inherent safety of DEAD when dissolved in different reagents by using differential scanning calorimetry and a thermal activity monitor III. The thermokinetic parameters, exothermic onset temperature (To), time to maximum rate under isothermal conditions (TMRiso), and apparent activation energy (Ea), were determined in order to reveal factors influencing the reaction mechanism. Comparing with pure DEAD, T0 was lower when DEAD was dissolved in three ionic liquids: 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl)imide. Additionally, Ea and TMRiso were considerably higher, indicating there was an improvement in both efficiency and thermal safety of DEAD for the reaction process. These results support the applications of DEAD in industrial process safety, and set a foundation for future laboratory investigation.

Macrocharacteristics of gaseous indicator products and exothermicity during low-temperature oxidation of samples from different regions of the same coal seam from Huainan, Anhui, China

To study the similarities and differences in the macrocharacteristics of a coal seam during low-temperature oxidation at different regions of the same coal mine, six coal samples from the 13-1 seam were selected from Huainan, Anhui, China. The macroscopic spontaneous combustion characteristics, including the gaseous products and characteristic temperatures, during the low-temperature oxidation of samples from different regions of the same coal seam, were studied using a temperature-programmed test. The results revealed that the characteristic temperatures of the samples from the coal seam were close to each other, the critical temperature range was 70–80 °C, and the crack temperature range was 90–100 °C. The CO/O2 ratio varied considerably. Thus, the degree of incomplete oxidation reaction to release CO was different at different regions in the coal seam. Moreover, the variation in the CO/CO2 ratio of the samples from the coal seam was similar. A calorimeter (C80 Calvet, SETARAM, France) was adopted to explore the exothermic characteristics of the coal seam during low-temperature oxidation. The exothermic onset temperature of the samples from the coal seam was similar, with a range of 50.1–54.3 °C. Differences were observed in the total thermal energy released by oxidation at low temperature in the samples from the coal seam; however, the percentage of thermal energy release at low temperature and that during the entire oxidation process was similar. The changes in the apparent activation energy of coal specimens from the seam were similar. It was, and is, important to investigate the prediction and prevention technique of spontaneous combustion in regional coal seams.

Thermal hazard evaluation of tert-butylperoxy-2-ethylhexanoate mixed with H2O and NaOH solution

Tert-butylperoxy-2-ethylhexanoate (TBEC)—an easily decomposable organic peroxide—is widely used as a polymerization initiator in industrial production. Sodium hydroxide solution and water are common impurities in the polymerization process. In this study, exothermic onset temperature (T0) and heat of decomposition (ΔH) of TBEC with impurities were obtained through differential scanning calorimetry. In addition, maximum pressure (Pmax), maximum temperature (Tmax), and adiabatic temperature rise (ΔTad) were obtained through accelerated rate calorimetry (ARC). Apparent activation energy (Ea) scores for pure TBEC and TBEC mixed with water (TBEC/H2O) and sodium hydroxide (TBEC/NaOH) were calculated. Subsequently, based on experimental data obtained through ARC, the self-accelerating decomposition temperature and temperature at the time to maximum rate under adiabatic conditions were calculated for 24 h (TD24) and 8 h (TD8). The experimental results indicated that H2O negligibly affected T0 but decreased ΔH, Pmax, Tmax, and ΔTad. Moreover, addition of H2O increased the TD24 and TD8 of TBEC. Thus, the thermal hazard of TBEC was reduced by addition of H2O. Addition of NaOH solution increased the complexity of the reaction because the initial decomposition temperature and activation energy were negatively correlated to the content of NaOH in the solution.

Overcharge cycling effect on the thermal behavior, structure, and material of lithium-ion batteries

The present study investigates the overcharge cycling effect on thermal behavior, structure, and electrode material of lithium-ion batteries (LIB) with a Lix(Ni0.3Co0.3Mn0.2)O2 cathode. The thermal behavior of LIBs with different overcharged degrees was studied using vent sizing package 2 and differential scanning calorimetry. Changes in the internal composition of the batteries during overcharge were observed using a scanning electron microscope and an inductively coupled plasma optical emission spectrometer. The results indicate that the overcharge process can be divided into four stages. A battery was more likely to trigger thermal runaway during overcharge under adiabatic conditions than in an ambient environment. During overcharge, the surface temperature of a 150% state-of-charge (SOC) battery was approximately 3.0 °C higher than that of a 100% SOC battery. Because of generated gas and lithium deposition during overcharge cycling, the battery thickness increases and coulombic efficiency decreases. The apparent exothermic onset temperature (T0) of a battery with 150% SOC was 87 °C below that of a 100% SOC battery. Cathode material becomes highly reactive when the battery was overcharged to 150% SOC. Here, the released heat was 1026.4 J/g. These results provide feasible support for understanding the overcharge mechanism and battery management system.

Thermal kinetic analysis of exothermic nature and cupric ion catalysis of electronic-grade etching solutions by using calorimetry

Wet etching is a fundamental process in the electronic industry, particularly in the production of liquid crystal display panels, integrated circuit wafers, and printed circuit boards. Various electronic-grade etchants, such as Cu-etchant, Al-etchant, and sodium persulfate (SPS)-etchant, have been used for etching process. Furthermore, the Cu-etchant, which contains hydrogen peroxide and concentrated acids, are widely used in panel etching nowadays owing to its high etching rate and ease of regeneration. Nonetheless, high-tech industries that use etchants should consider their hazardous properties, such as explosiveness, flammability, and corrodibility. This study evaluated the exothermic nature and incompatibility of the Cu-etchant in the storage tanks and etching tools. Understanding the exothermic and runaway hazards of the Cu-etchant and its reaction with cupric ion catalyst is necessary in case the etching process fails due to mixing, contamination, or lack of temperature control. Data of thermal dynamic scanning on various etchants can ascertain the exothermic onset temperature (T0), peak power, and exothermic enthalpy (ΔH). Reaction kinetic data were evaluated after comparison with various etchants' exothermic behaviors. Moreover, various self-heating models (dT/dt) of thermal decompositions for the Cu-etchant and its cupric-ion catalysis were proposed using thermokinetic analysis methods for improving the safety of operation while conducting etching process.

Thermal stability evaluation of multiple tubes of fireworks by calorimetry approaches

Fireworks are constructed of powder and other materials that can readily release light and heat by oxidation reaction. Pyrotechnic compositions are highly susceptible and readily result in explosive decomposition. Fireworks have led to numerous accidents during their manufacture, storage, and display. Water as an impurity affects the decomposition properties of fireworks, and consequently influences their emission safety. This research focused on the thermal stability of multiple tubes of propellant, effect pieces, and propellant mixed with water using differential scanning calorimetry (DSC) and thermokinetic analysis. The thermokinetic method was employed to determine the apparent activation energy and predict the long-term stability of dry and humid propellants. According to the predicted results, the decomposition of dry and humid propellants was severely limited after 30 days at an isothermal condition of 80 °C. However, the DSC tests indicated that water could substantially influence the heat release, emission ability, and sensitivity of the propellant. The exothermic peak for the humid propellant was ca. 275 °C, which was lower than dry propellant of 318 °C. The water visibly diminished the heat emitted from and peak intensity of the propellant. Insufficient energy supply might result in lower emission height, and lower exothermic onset temperatures in wetted propellant could lead to faulty ignition times. Therefore, contact with water (that could lead to water infiltration) should be avoided to increase the probability of successful launching and ignition.

Complex thermal analysis and runaway reaction of 2,2′-azobis (isobutyronitrile) using DSC, STA, VSP2, and GC/MS

A severe manufacturing accident involving 2,2′-azobis (isobutyronitrile) (AIBN) occurred in China on April 14, 2011, which created high-pressure gas release killing nine people and severely damaging equipment and buildings. Eliminating chemical catastrophes in the petrochemical industry is a global concern. A new approach, which combines non-isothermal kinetic modeling, runaway reaction, and product analysis, was employed to determine decomposition mechanisms of AIBN by separately using differential scanning calorimetry, simultaneous thermogravimetric analyzer, vent sizing package 2, and gas chromatography/mass spectrometer. The results indicated that azo compound AIBN exhibits higher level of thermal decomposition with a maximum temperature of 294 °C and maximum pressure of 367 psig in comparison to the other azos. Moreover, various critical thermokinetic parameters, such as time to maximum rate, exothermic onset temperature, adiabatic temperature rise, and pressure gradients were obtained. A combination of thermal hazards and reaction pathways was subsequently employed to investigate the thermokinetics and mechanisms of AIBN decomposition.