RSC Advances
·
2019
·Vol. 9
·期 15
·8415-8425
·
IF 3.049
Jing Li,Chuanfu Zhang,Ruiming Yin,Wenhai Zhang
In this work, the pyrolysis characteristics of a low-toxic N,N-dimethylacrylamide (DMAA) gel polymer was investigated through nonisothermal thermogravimetry (TG) and TG-FTIR analyses. Moreover, the thermal debinding kinetics of gelcast SiAlON ceramic parts was studied through three different kinetic models: the Coats–Redfern (C–R) method, distributed activation energy model (DAEM) and three-Gaussian-DAEM-reaction model (3-DAEM). The rationality and adaptability of the three models to the thermal debinding kinetics study were analyzed by comparison with experimental data. The results showed that three mass loss zones were observed in the temperature ranges of 100–320 °C, 320–520 °C and 520–600 °C, respectively, and the main pyrolysis gas products were CO2, H2O and CH4. The conversion rate (α) curves calculated by 3-DAEM were more consistent with the experimental values than those calculated with the C–R and DAEM methods. The fitting quality parameter (Fit%) was less than 2.63%, and the reaction rate (dα/dT) curves calculated by 3-DAEM were bimodal distribution curves, which were in good agreement with the experimental results. The kinetic parameters (E0,i, k0,i and σi) of the global thermal debinding process calculated by 3-DAEM were 116.00–145.79 kJ mol−1, 1.10 × 109 s−1 and 1.67–43.25 kJ mol−1, respectively. It is anticipated that the study achievements can be used to help predict the thermal debinding behavior and design a reasonable debinding technology for the gelcasting of ceramic parts.
研究领域:
材料科学
·
化学工程
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DOI
PubMed
高影响因子
RSC Advances
·
2014
·Vol. 4
·期 59
·31249-31260
·
IF 3.708
Yang Meng,Junfeng Chu,Jiajia Xue,Chaohao Liu,Zhen Wang,Liqun Zhang
Although polysiloxane elastomers have many merits, their fast crystallization at low temperature is problematic in some fields. In this study, a novel non-crystallizable, low-Tg epoxidized polysiloxane (ESR) with functional epoxy groups in side chains was designed and synthesized though two steps: (i) the preparation of poly(methylvinylsiloxane) (SR) by anionic ring-opening copolymerization of 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl cyclotetrasiloxane and octamethylcyclotetrasiloxane, and (ii) the subsequent epoxidation of the SR. Reaction kinetic studies demonstrated that the epoxidation of SR was a second-order reaction and more than 90% of the double bonds were converted into epoxy groups during the epoxidation. Despite a slight increase in the Tg of ESRs as the content of epoxy groups increased, the low-temperature performances of ESRs were greatly improved because of the inhibition of the crystallization of polysiloxane chains. Surprisingly, the ESRs also showed higher thermal degradation temperatures than the traditional poly(dimethylsiloxane) did. The excellent low-temperature performance and high degradation temperatures endowed the ESR with great potential as an elastic material in the aerospace industry where materials have to undergo very high and low temperature.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2022
·
IF 5.546
Ge Zhu,Haoji Lao,Feng Feng,Minyan Wang,Xingzhong Fang,Guofei Chen
Two series of poly(amide imide)s (PAIs) based on two novel isomeric amide-containing diamine monomers and different commercial aromatic dianhydrides were synthesized via thermal imidization. These PAIs exhibited excellent T g s ranging from 368 to 431 °C, low coefficients of thermal expansion (CTE) of 6.7–47.2 ppm/K, and good 5% weight loss temperatures ( T d5% s) in N 2 of 494–540 °C, which was attributed to the introduction of rigid backbone and strong intermolecular hydrogen bonding resulted from amide bond. In particular, PAI-1a and PAI-1b displayed well-balanced performance with T g s in the range of 419–431 °C, CTE in the range of 6.7–9.0 ppm/K, and mechanical properties with tensile strengths of 116–125 MPa, tensile moduli of 8.4–8.7 GPa, which could be probably used in flexible displays. In addition, the effects of two isomeric monomers on the properties of films were compared, and it was found that PAI-(1 – 3)a showed higher T g, T d5% and CTE, but lower tensile strength and transparency than PAI-(1 – 3)b .
研究领域:
高分子化学
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材料科学
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DOI
高影响因子
COMPOSITE STRUCTURES
·
2023
·
IF 6.3
Xiaofei Wang,Yang He,Xinli Xiao,Wei Zhao,Jinsong Leng
In order to enhance the thermal conduction property and shorten response time of shape memory polyimide (SMPI), “spot-plane” directional thermally conductive acidified graphene/AlN/SMPI composites were prepared, in which AlN nanoparticles were used as “thermal conduction spots” and acidified graphene was used as two-dimensional “thermal conduction planes”. The SMPI composite doped with 6 wt% AlN and 0.8 wt% acidified graphene had good heat conducting properties (the in-plane thermal conductivity of 5.90 W m −1 K −1 ), excellent mechanical propertied (the tensile strength of 134.5 MPa, and Young’s modulus of 3.8 GPa), high shape memory transition temperature (at 419 ℃), and great thermal stability and shape memory properties. Compared with SMPI resin matrix, the response time of the acidified graphene/AlN/SMPI composite was shortened by 140 s, only 20 s, and it can be applied in flexible electronics, intelligent response structures and active deformation structures in high-temperature environment.
研究领域:
材料科学
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复合材料
·
热传导工程
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DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 138
·期 46
·51364
·
IF 3.125
Huimin Zhang,Dan Meng,Wenjia Wang,Hongfei Li,Xiaoyu Gu,Sheng Zhang,Jun Sun,Fei Xin,Zuodong Qin,Wufei Tang
A modified kaolinite by grafting with phytic acid (PA-g-Kaol) is fabricated, and it was introduced into ethylene vinyl acetate (EVA) with intumescent flame retardancy (IFR) together to improve the flame retardancy of EVA composites. The results show the limiting oxygen index value of EVA/ (18.0 wt% IFR)/ (2.0 wt% PA-g-Kaol) is 30.8%. Meanwhile, there is only one dripping produced in the vertical burning test. What's more, the flame-retardant mechanism is demonstrated by TG-IR, real-time-IR and GC–MS analysis. The results indicate that some pyrolytic products of IFR and PA-g-Kaol, like ammonia and phosphoric acid, catalyze the crosslinking of EVA and flame retardant, the resultant compact char protects the substrate from further burning.
研究领域:
材料科学
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聚合物化学
·
消防安全工程
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DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2023
·
IF 6
Guofei Chen,Gang Xu,Yang Jiao,Yongmei Tang,Liyun Tan,Xingzhong Fang
Two series of transparent cardo polyimides (PIs) derived from bisphenol fluorenes and 1,4-bis(4-fluorophthalimide)cyclohexanes (BFCH) with different ratios of trans- and cis - 1,4-diaminocyclohexane were prepared via aromatic nucleophilic substitution. These PIs exhibited high glass transition temperatures ( T g s) of 271–352 °C, 5% weight loss temperatures ( T d 5% ) of 400–433 °C in nitrogen, mechanical properties of tensile strengths of 62–107 MPa, tensile moduli of 3.0–4.4 GPa and elongations at break of 1.7–4.5% and great solubility in a variety of organic solvents. These PI films appeared excellent optical transparency, which displayed the cut-off wavelengths from 323 to 355 nm and high transmittance at 450 nm with more than 85 %. The steric effects of different substituent groups on bisphenol fluorene and different ratios of trans / cis configuration were also investigated.
研究领域:
材料科学
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化学工程
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DOI
高影响因子
CANADIAN JOURNAL OF CHEMICAL ENGINEERING
·
2018
·Vol. 96
·期 12
·2586-2592
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IF 1.265
Renjie Deng,Kuiyi You,Fangfang Zhao,Pingle Liu,He'an Luo
In this work, a simple method for the highly selective preparation of valuable dinitronaphthalene from 1-nitronaphthalene employing NO 2 as a nitrating agent has been developed. The results demonstrated that HY zeolite as an eco-friendly and stable catalyst exhibits good catalytic performances. The total selectivity to valuable dinitronaphthalene compounds including 1,5-, 1,4-, and 1,3-dinitronaphthalene can reach 87.6 % in our present nitration reaction. Meanwhile, the physico-chemical properties of catalysts were characterized by XRD, FTIR, TG/DTG, BET, and NH 3 -TPD, and the probable nitration reaction mechanism was also suggested in this paper. The present nitration process seems to be a mild, eco-friendly, and economical route for the preparation of valuable dinitronaphthalene compounds.
研究领域:
化学工程
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催化
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环境化学
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DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2020
·
IF 3.408
Bo Li,Hansheng Leng,Wei Liu
A new low-temperature sintered microwave ceramic Ca 5 Ni 2 Mg 2 V 6 O 24 (CNMVO) was synthesized by a solid-state reaction method. The effect of sintering process on microstructures and microwave properties of CNMVO ceramics was investigated in detail. XRD results and EDS analyses show that CNMVO ceramics sintered at 850–925 °C are the uniform solid solution with a stable cubic garnet structure. The CNMVO ceramic sintered at 875 °C has the highest Q × f value and is accompanied by the volatilization of vanadium observed by SEM . TG curves demonstrate that the increase of heating rate weakens the vanadium loss. According to the Raman spectra , the Q × f value reaches the maximum value at a heating rate of 2 °C/min, because of the highest cation ordering degree and the densest packing fraction caused by the properly deficient vanadium. As a result, the Ca 5 Ni 2 Mg 2 V 6 O 24 ceramic sintered at 875 °C with a heating rate of 2 °C/min exhibits the best microwave properties: ε r = 8.07, Q × f = 60,613 GHz, and τ f = −32 ppm/°C.
研究领域:
材料科学
·
陶瓷
·
微波工程
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DOI
高影响因子
FUEL
·
2022
·
IF 8.035
Zhanshi Ni,Haobo Bi,Chunlong Jiang,Hao Sun,Wenliang Zhou,Zhicong Qiu,Qizhao Lin
Faced with increasingly severe environmental and energy issues, the development and utilization of solid waste have become a trend. In this study, a thermogravimetric-Fourier infrared spectrometer-mass spectrometer (TG-FTIR-MS) was used to carry out the co-pyrolysis experiment of coal slime and cellulose. The samples with mass mixing ratios of 0:10, 1:9, 3:7, 5:5, 7:3, 9:1, and 10:0 were pyrolyzed in N 2 atmosphere. The percentages of mass loss during the pyrolysis of coal slime and cellulose were 15.69 and 94.28%, respectively. The addition of cellulose to the coal slime could significantly improve the pyrolysis performance of the sample. It was detected by FTIR that the pyrolysis of the blends mainly formed C=O-containing compounds. MS was used to monitor the ion current intensity of gaseous products of sample pyrolysis online. The average activation energy of the reaction between coal slime and cellulose calculated by the Kissinger-Akahira-Sunose method were 237.59 kJ/mol and 174.06 kJ/mol, respectively. The principal component 1 and principal component 2 dominated the co-pyrolysis process of coal slime and cellulose. The MAE, RMSE, and R 2 of the artificial neural network prediction model for predicting the pyrolysis process of the sample were 0.5249, 0.8244, and 0.9994, respectively. This research provided basic theory and data support for understanding the co-pyrolysis of coal slime and biomass.
研究领域:
能源化学
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环境科学
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热化学转化
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可再生能源
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固体废物利用
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DOI
高影响因子
POLYMER
·
2019
·
IF 3.771
Yiyao Tian,Longbo Luo,Qiqi Yang,Lingjie Zhang,Ming Wang,Difeng Wu,Xu Wang,Xiangyang Liu
Low coefficient of thermal expansion (CTE) in the range of 40–400 °C is a crucial factor for polyimide (PI) films serving as the flexible substrate for display devices. The introduction of hydrogen bonds (H-bonds) is an effective method to obtain high Tg and low in-plane CTE below polyimide (PI) film. However, these H-bonds commonly exhibit low thermal stability and would be ruptured at high temperature (>300 °C), which leads to a remarkable increase of CTE. Herein, we report a strategy to improve thermal stability of H-bonds at the high temperature via intermolecular crosslinking. For neat PI, its in-situ FTIR results confirm severe dissociation of H-bonds above 300 °C, While after the crosslinking reaction, the content of strong H-bonds at 400 °C is 110% higher than that of neat PI, which indicates this intermolecular crosslinking restrains dissociation of H-bonds. Correspondingly, CTE values of crosslinked PI films at 300 o C–400 °C are sharply decreased from 33.8 ppm/K to 6.0 ppm/K. Moreover, decrease of in-plane orientation accompanying lower CTEs in crosslinked PI deviates from common rule reported in linear PIs, implying the important roles of H-bonds and crosslinking. More over, the contribution of H-bonds and crosslink to the decrease of CTE are performed by Pearson correlation analysis and the results indicate that the decrease of CTE in crosslinked PIs at low temperatures is completely attributed to confinement effect of crosslinking, but contribution of stable H-bonds becomes more prominent above 300 °C. Consequently, the obtained PI films exhibit ultra low CTE (1.9 ppm/K) at the range of 40 o C–400 °C, along with high Tg (>450 °C) exhibiting great potential for flexible-display substrates.
研究领域:
材料科学
·
高分子化学
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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
·
化学动力学
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产品关联
DOI
高影响因子
POLYMER
·
2026
·
IF 5.1
Tianci Ma,Lei Yang,Jinglei Xing,Long Wang,Guofei Chen
It is a new challenge to develop fluorine-free transparent polyimides due to the prohibition of perfluoroalkyl and polyfluoroalkyl substances (PFAS). Hence, a series of fluorine-free polyimides were synthesized by 9,9-bis(3,4-dicarboxyphenyl) fluorene dianhydride (BPAF) with 3,3′-bis(methyl)-4,4′-benzidine (2,2′-DMBZ), 3,3′-bis(methyl)-4,4′-benzidine (3,3′-DMBZ), 1,4-diaminobenzene ( p -PDA), 1,3-diaminobenzene ( m -PDA), 2,6-toluenediamine ( m -MPDA) and 2,4,6-trimethyl-1,3-phenylenediamine ( m -TMPDA) through one-step and two-step methods. Then the corresponding polyimide films were obtained by solution casting. All polyimides exhibited high glass transition temperatures ( T g s) of 404-523 °C, coefficients of thermal expansion (CTEs) of 39-65 ppm/K, optical transmittances at 400 nm ( T 400 s) of 36-82 %, tensile strengths of 104.6-156.3 MPa, and tensile moduli of 2.6-4.3 GPa. The prepared fluorine-free polyimides had better performances than typical fluorine-containing polyimide derived from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2′-bis(trifluoromethyl)-4,4′-benzidine (TFDB). In particular, PI-6 exhibited comprehensive properties with T g of 523 °C, T 400 of 82%, and CTE of 42 ppm/K.
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DOI
高影响因子
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