THERMOCHIMICA ACTA
·
2021
·
IF 3.115
Jihe Zhao,Xuefeng Gui,Wenhai Zhang,Shudong Lin,Yuanyuan Tu,Jiwen Hu,Daguang He,Xiaohua Huang
Thermal runaway primarily occurs during the course of copolymerization due to the release of large amounts of heat. In this paper, the thermal risk associated with styrene-methyl methacrylate bulk copolymerization was firstly investigated by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC). The result found that the exothermic behavior was greatly affected by the initiator concentration, in contrast the exothermic enthalpy was not. This exothermic behavior was firstly illustrated via polymerization mechanism. The temperature and pressure have changed dramatically during the adiabatic runaway copolymerization, which demonstrated a great potential risk of thermal runaway. Kinetic parameters, such as T NR , T SADT was calculated accordingly, which provided guidance for the safety of storage and transportation. This study will provide a helpful safety assessment for the styrene-methyl methacrylate bulk copolymerization, which is widely used in industry.
研究领域:
化学工程
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材料科学
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安全科学
✓ 已验证
产品关联
DOI
高影响因子
QUIMICA NOVA
·
2025
·
IF 0.7
Li Xin Yi,Xing Zhi Xiang,Liu Ye Cheng,Cheng Yang,Huang An Chi
Nitroaromatic acids, ubiquitous intermediates in nitro compounds, find broad applications in pharmaceuticals and fine chemical industries, yet their safety often receives inadequate attention. This paper investigates the thermal decomposition process of three isomers of nitrobenzoic acid using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), complemented by calculations of the apparent activation energy using typical kinetic methods. The reaction type was verified using a nonlinear fitting method. Thermal safety parameters including the time to maximum rate (TMR), critical temperature of self-acceleration (TCL), and thermal risk index (TRI) were employed to elucidate the thermal hazards. The thermal decomposition mechanism was further explained using density functional theory (DFT) methods, focusing on the Mayer bond order. The findings revealed that the average apparent activation energies for p-nitrobenzoic acid (PNBA), m-nitrobenzoic acid (MNBA), and o-nitrobenzoic acid (ONBA) were 157.00, 203.43, and 131.31 kJ mol-1, respectively. A single n-order reaction characterized the thermal decomposition process. The TMR and TCL parameters indicated a decomposition tendency at high temperatures, with the thermal stability at elevated temperatures following the order: PNBA < ONBA < MNBA. The TRI parameter indicates the danger level of the nitrobenzoic acids. The thermal decomposition mechanism was elucidated using Mayer bond energies, offering valuable insights into storage and transportation, and contributing to developing predictive models for thermal characteristics.
研究领域:
化学工程
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安全科学
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计算化学
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产品关联
DOI
高影响因子
MACROMOLECULES
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2017
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IF 5.835
Qingsong Lian,Yan Li,Kai Li,Jue Cheng,Junying Zhang
The vulcanization mechanism remains unclear due to the difficulty of characterization and the complexity of the vulcanization systems. In this work, a series of epoxy model systems were used to study the sulfur cleavage behavior, from which the study process of the vulcanization mechanism was significantly simplified and a brand new sulfur-only vulcanization mechanism was revealed by the FTIR and DSC analysis. Our studies suggest that thiyl radicals derived from the homolytic cleavage of sulfur play the dominant role in the vulcanization, while the heterolytic fission of sulfur cannot occur as expected because this reaction needs 200 °C. Nevertheless, sulfur anions, which are easy to be understood derived from the heterolytic cleavage of sulfur, are actually transformed from the thiol groups that are produced through the reaction of thiyl radicals abstracting α-H atoms of allyl groups in rubber, and this maybe the reason that vulcanization mechanism remains controversial for centuries.
研究领域:
材料科学
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化学工程
✓ 已验证
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2017
·
IF 4.811
Xi Chen,Nan Zheng,Qiao Wang,Lingzhi Liu,Yongfeng Men
The differences in side chain crystallization behavior between cellulose esters (CEs) and hydroxypropyl cellulose esters (HPCEs) were systematically investigated by a combination of differential scanning calorimetry (DSC) and small and wide-angle X-ray scattering techniques. DSC investigation indicated that under the same side chain length, the fusion enthalpy and the number of crystallized CH 2 of CEs were smaller than HPCEs. At the same time, their d-spacing and molecular arrangements were also different from each other. For the CEs, the side chains are perpendicular to the main chain, while the side chains most probably tend to tilt to main chain in the HPCEs as was evidenced by X-ray scattering results. The phenomenon can be understood as a consequence of different flexibility of attachment bridges in both kinds of side chain polymers and the steric hindrance of methyl group in the hydroxypropyl group in HPCEs. In addition, the added hydroxypropyl substituents make the side chain length increasing.
研究领域:
材料科学
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高分子化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
EUROPEAN JOURNAL OF PHARMACEUTICAL SCIENCES
·
2018
·
IF 3.466
Wei Wang,Chao Liu,Zheng Luo,Xiaocao Wan,Liang Fang
The aim of present study was to develop an oxybutynin (OXY) transdermal patch with good permeation behavior and mechanical property. Special attention was paid to the effect of chemical enhancer on the molecular mobility of pressure sensitive adhesive (PSA) at molecular level. PSAs and permeation enhancers were investigated through in vitro experiment using rat skin. The optimized formulation was evaluated through pharmacokinetic study using rat. In addition, the molecular mechanism of sorbitan monooleate (Span® 80) in the improvement of PSA molecular mobility was investigated using FT-IR, molecular dynamics simulation, DSC and rheological study. As a result, the optimized formulation using amide PSA demonstrated good adhesion property. And the AUC 0-t and C max of optimized patch were 6435.8 ± 747.8 h ∗ ng/mL and 127.8 ± 18.0 ng/mL, respectively, which had no significant difference with commercial product. Furthermore, the improvement of the PSA mobility by Span® 80 rather than the decrease of interaction between drug and PSA was the main factor that enhanced the release of OXY from patch. In conclusion, a drug-in-adhesive OXY patch was developed, and the effect of PSA molecular mobility increase on the enhancement of drug skin permeation was proposed at molecular level.
研究领域:
药剂学
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生物医学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
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2020
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IF 5.065
Shengbo Zhu,Wei Li,Bingyang Lu,Weixing Chen,Wenzhi Zhang,Xiaoling Niu,Xinbing Chen,Zhongwei An
Two series of terminal epoxy compounds, PmOBC (m = 1, 2, 3, 4) and P1OBEn (n = 6, 8, 10, 12), were synthesized for investigating the effect of epoxidation on mesomorphic and thermal stabilities. Molecular polarization and configuration obtained by DFT calculations can provide theoretical perspective. In addition, thermal stability is evaluated by the combination of DSC , TGA , and 1 H NMR. Compared with the corresponding alkenyl compounds, epoxidation reduces the molecular dipole moment and increase the molecular steric effect , which is not conducive to the formation of LC phases, but the reduced intramolecular energy may be helpful to improve thermal stability. Therefore, these terminal epoxy LCs are very promising for application in display devices requiring extremely high-temperature environments.
研究领域:
材料科学
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物理化学
✓ 已验证
产品关联
DOI
高影响因子
FLUID PHASE EQUILIBRIA
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2021
·
IF 2.775
Zhenxing Cai,Hui Zhao,Xin Zhou,Xiaobo Chen,Chaohe Yang
Solid-liquid equilibria of three binary mixtures consisting of para-xylene, ortho-xylene, meta-xylene and ethylbenzene were investigated in this study using differential scanning calorimetry (DSC) method, the mixtures were cooled to -120 °C and then heated to 20 °C at different heating rates, eutectic phase diagrams were observed for para-xylene/ortho-xylene and para-xylene/meta-xylene binary systems. The freezing point of pure ethylbenzene at atmospheric pressure is around -95 °C, but due to the effect of induction time, the observed freezing temperature is lower than -120 °C, the operation temperature of industrial xylene crystallization separation process is higher than -80 °C traditionally, therefore ethylbenzene will not crystallize in practical process, the phase diagram for para-xylene/ethylbenzene was not achieved. The experimental data were compared with data from other literatures and new features were found. The data were well correlated by Apelblat equation and λ H equation, it is significative to provide important engineering data for the separation and purification of xylene mixtures.
研究领域:
化学工程
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热力学
✓ 已验证
产品关联
DOI
高影响因子
Catalysts
·
2020
·Vol. 10
·期 3
·331
·
IF 3.52
Ergang Yao,Siyu Xu,Fengqi Zhao,Taizhong Huang,Haijian Li,Ningning Zhao,Jianhua Yi,Yanjing Yang,Changjian Wang
The fiber-like bis-(dimethylglyoximato) nickel(II) complex, Ni(DMG)2was successfully synthesized. The obtained samples were characterized by SEM-EDS, FT-IR, XRD, and XPS. The TG-DSC-FTIR-MS coupling technique was used to characterize the thermal decomposition behavior and evolved gas analysis of Ni(DMG)2. The non-isothermal decomposition reaction kinetic parameters were obtained by both combined kinetic analysis and isoconversional Vyazovkin methods. It was found that Ni(DMG)2begins to decompose at around 280 °C, and a sharp exothermic peak is observed in the DSC curve at about 308.2 °C at a heating rate of 10 °C·min−1. The main gaseous products are H2O, NH3, N2O, CO, and HCN, and the content of H2O is significantly higher than that of the others. The activation energy obtained by the combined kinetic analysis method is 170.61 ± 0.65 kJ·mol−1. The decomposition process can be described by the random nucleation and growth of the nuclei model. However, it was challenging to attempt to evaluate the reaction mechanism precisely by one ideal kinetic model.Keywords:nickel (II) complex;dimethylglyoxime;thermal behavior;kinetic analysis;combustion catalyst
研究领域:
材料科学
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化学动力学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED MICROBIOLOGY
·
2025
·
IF 3.2
Zhang Chuhan,Qin Lijun
AimsTo determine the optimum conditions for extracting Eucommia ulmoides gum (EUG) from Eucommia ulmoides leaves during fermentation by Coprinellus disseminatus. At the same time, the EUG characteristics were characterized.Methods and resultsThe ability of C. disseminatus to secrete degrading enzymes, including enzyme activity and lignocellulose content, was observed by culturing C. disseminatus on a medium with different formulations. Based on the optimal formula, the fermentation conditions were determined by an orthogonal test and EUG was extracted. After that, the characteristic parameters of EUG were determined by FT-IR, 1H-NMR, SEM, POM, DSC, XRD and GPC. The results showed that the lignin and hemicellulose contents in Eucommia leaves decreased significantly with the increase of fermentation days, and C. disseminatus mediated fermentation had an obvious damage effect on the tissue of Eucommia leaves. At the same time, At the same time, xylan can be used as an initiator to induce the expression of degradation-related enzymes. The extraction yield of EUG from Eucommia ulmoides leaves after fermentation was 3.06%, which was significantly improved. The optimum fermentation conditions were 4% inoculum, 28°C fermentation temperature, and pH = 5. The results of infrared FT-IR and 1H-NMR showed that the extract had typical characteristics of EUG, and the surface and quenching part of the EUG were smooth, as observed by SEM. In addition, DSC and XRD analysis show that there are two crystal types, α and β, in the crystallization process of molten EUG. The main crystallization type of EUG extracted from fermented leaves was β type.ConclusionThe ability of C. disseminatus to produce degrading enzymes can effectively improve the extraction rate of EUG under optimal fermentation process. The method can maintain the integrity of gutta-percha better. EUG has the characteristics of good crystallinity, many β crystal types and high molecular weight.
研究领域:
生物技术
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生物化学
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材料科学
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植物学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Nanomaterials
·
2022
·Vol. 12
·期 13
·2249
·
IF 5.719
Rui Cai,Jinlong Zhao,Naixin Lv,Anqing Fu,Chengxian Yin,Chengjun Song,Min Chao
Herein, the curing kinetics and the glass transition temperature (Tg) of MXene/phenolic epoxy composites with two curing agents, i.e., 4,4-diaminodiphenyl sulfone (DDS) and dicyandiamine (DICY), are systematically investigated using experimental characterization, mathematical modeling and molecular dynamics simulations. The effect of MXene content on an epoxy resin/amine curing agent system is also studied. These results reveal that the MXene/epoxy composites with both curing agent systems conform to the SB(m,n) two-parameter autocatalytic model. The addition of MXene accelerated the curing of the epoxy composite and increased theTgby about 20 K. In addition, molecular dynamics were used to simulate theTgof the cross-linked MXene/epoxy composites and to analyze microstructural features such as the free volume fraction (FFV). The simulation results show that the introduction of MXene improves theTgandFFVof the simulated system. This is because the introduction of MXene restricts the movement of the epoxy/curing agent system. The conclusions are in good agreement with the experimental results.Keywords:MXene;epoxy resin;amine curing agent;curing kinetics;molecular dynamic simulations;non-isothermal DSC
研究领域:
材料科学
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化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
COMBUSTION AND FLAME
·
2023
·
IF 4.4
Jian Wang,Jie Chen,Yaofeng Mao,Xingquan Zhang,Jun Wang,Fude Nie
Metal fuel with high energy and reactivity is an urgent need for the development of solid propellant, explosive and pyrotechnics. Herein, spherical B/Al/PTFE fuel is designed based on synergistic reaction effect between B/F and Al/F and prepared through the confinement-emulsion-templated method. The combustion reaction performance and pressure output performance of B/Al/PTFE microspheres are much better than their physically mixed counterparts. The synergistic reaction effect between B/F and Al/F on the reaction heat, flame propagation , and pressure output were systematically investigated through adjusting the B/Al mass ratio (30/0∼0/30). The DSC results show that the highest heat of combustion of 4904 J/g can be achieved when the B/Al mass ratio is 21/9. Furthermore, the combustion duration , peak pressure, and pressurization rate are monotonically accelerated from 653 ms, 352.15 kPa, and 305.67 MPa/s to 200 ms, 821.25 kPa, and 1831.18 MPa/s, respectively. This work provides a promising method for the design and preparation of highly composited metal fuel for practical application.
研究领域:
材料科学
·
能源工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
·
2024
·Vol. 149
·期 10
·4491-4503
·
IF 3
Chen Yongjia,Zhao Yilin,Hua Min,Pan Xuhai,Jiang Huichun,Jiang Juncheng
We investigated the inhibition of thermal runaway of styrene polymerization by DNPB. DNBP is an inhibitor in styrene polymerization reaction. Polymerization is one of eighteen hazardous processes. Styrene polymerization reaction is characterized by high heat production and fast reaction rate. Firstly, differential scanning calorimetry (DSC) and adiabatic calorimetry (ARC) were chosen to study the effect of different mass of DNBP on thermal behavior in non-isothermal and adiabatic environments. Secondly, exploring the inhibitory effect of DNBP at different runaway temperatures using an oil bath reactor. The results showed that when DNBP was at 0.80%, effective inhibition was obtained at different runaway temperatures. Finally, GC/MS and Gauss16 were used to infer the mechanism of inhibition in terms of macroscopic products and microscopic instabilities. The results showed that the products of the oil bath reactor experiments were related to the mass of DNBP, and when DNBP was 0.80%, the products increased and the main reaction was inhibited. Finally, it was deduced that the nitro group undergoes a possible path of direct addition reaction with the styrene radical before bond breaking.
研究领域:
化学工程
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材料科学
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安全工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）