Polymers
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2022
·Vol. 14
·期 23
·5233
·
IF 4.967
Chunhua Lou,Siyu Jiang,Yongli Zhou,Xiaohua Gu,Yong Zhang,Xianzhi Kong
A modified corn straw (CS)/epoxy resin (EP) composite was prepared using bisphenol A EP (i.e., E-51) as matrix, 2-methylimidazole as curing agent, and CS modified by 3-glycidyl ether oxypropyl trimethoxysilane (KHCS) as filler. Its chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR). The dynamic thermodynamic properties, mechanical properties, flame retardant property, and fracture morphology were studied using dynamic mechanical analysis (DMA), a universal testing machine, a micro combustion calorimeter, and a scanning electron microscope (SEM), respectively. The effects of different contents of KHCS on various properties were discussed. The experimental result showed that the CS was bonded toKH560 by a covalent bond. The impact strength, tensile strength, and flexural strength of the composites were all improved compared with those of pure EP. When the content of KHCS was 15 wt%, the maximum impact strength of the composites was 3.31 kJ/m2, which was 1.43 times that of the pure EP. The p HRR and THR of MCSEC-20 were 512.44 W/g and 25.03 kJ/g, respectively, which were 40.71% and 27.76% lower than those of pure EP, when the content of KHCS was 20 wt%. Moreover, the mechanism of the curing composites was investigated.Keywords:epoxy resin;corn straw;composites;preparation;curing mechanism
研究领域:
材料科学
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化学工程
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产品关联
DOI
PubMed
高影响因子
Advanced Composites and Hybrid Materials
·
2021
·Vol. 5
·期 1
·322-334
·
IF 5.693
Fan Xiaotian,Liu Zhanxin,Huang Jianguang,Han Ding,Qiao Zihe,Liu Huihui,Du Jie,Yan Hui,Ma Yuanyuan,Zhang Congyun,Wang Zhi
The development of materials with high thermal stability and good hydrophobicity is important in the field of coatings. Fluorinated benzoxazines are good choices for coating applications; however, fundamental discussion among structure, curing mechanism, and properties is still scarce. Thus, a series of new fluorinated benzoxazines, including totally new meta - fluoroaniline-, ortho-fluoroaniline-, and para-fluoroaniline-based benzoxazine, is successfully synthesized. The effect of different substituted positions of fluorine atoms on the curing mechanism, thermal stability, and surface properties of polybenzoxazines is discussed in detail based on experimental and theory analysis. The structural and geometrical parameters were investigated by NMR ( 1 H, 19 F) and FTIR spectroscopy. The curing peak temperature of fluorine-substituted benzoxazines was found to be in order of meta - fluoroaniline benzoxazine (m-Bf, 235.9 °C) < para-fluoroaniline benzoxazine (p-Bf, 244.4 °C) < ortho - fluoroaniline benzoxazine (o-Bf, 262.7 °C). Furthermore, the density functional theory (DFT) was used for quantitative analysis to determine the effect of fluorine atom position on the curing mechanism of benzoxazine for the first time. Moreover, the thermal stability (at 10% weight loss temperature) for different cured polybenzoxazines was found to be in the order of m-Bf (323.4 °C) < o-Bf (289.1 °C) < p-Bf (255.5 °C), and the hydrophobicity was in the order of m-Bf (121.4°) < o-Bf (119.3°) < p-Bf (106.3°). Meanwhile, the coatings based on fluorinated polybenzoxazines also have shown excellent mechanical and anti-corrosion properties. In this paper, not only new benzoxazines that can be used as coatings and composites are provided, but a deep understanding of the relationship among structure, curing mechanism, and performance of fluorinated benzoxazines is got. Graphical abstract Three fluorinated benzoxazines were synthesized and corresponding curing mechanism, thermal stability and possible application were discussed and showed.
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
POLYMER DEGRADATION AND STABILITY
·
2020
·
IF 4.032
Peng Wang,Ming Liu,Qichao Ran
Based on the weight loss and small molecule volatiles released during the thermal curing process of three kinds of benzoxazines , bisphenol A/aniline type benzoxazine (BA-a), p-cresol/diamine type benzoxazine (MPH-mda) and 2,4-xylenol/4,4′-methylenebis-(2,6-diisopropyl) aniline type benzoxazine (DMPH-mdpa), their curing mechanisms and the weight-loss mechanisms were studied. The weight-loss ratios and structure changes of these benzoxazines during the curing process were studied by weighing method, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The volatiles released from these benzoxazines during different curing stages were collected by a self-made experimental device. The structures of these volatiles were characterized by FTIR and proton nuclear magnetic resonance spectroscopy ( 1 H NMR). The results showed that the mixtures of imine , triazine , aniline and Schiff base were released from the cracking of the intermediate during the thermal curing of BA-a. Compared with BA-a, the weight loss of MPH-mda was smaller, and its volatile was a small amount of stable diamine type Schiff base. For DMPH-mdpa, because all active reaction points on benzene ring were occupied by alkyl groups , it cannot form effective polymer structures after ring-opening reactions, which led to that DMPH-mdpa had the most weight loss during the curing process, and mainly generated phenol type volatiles.
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
ChemistrySelect
·
2025
·Vol. 10
·期 29
·e00501
·
IF 2
Junjie Zhou,Chaoen Jin,Fan Wang,Yaping Zhu,Huimin Qi
Graphical Under aromatic amine catalysis, the cyanate ester/epoxy system reached 80.6% curing after 5 days at room temperature. Research indicates that adding 20% epoxy resin to pure cyanate ester increases the oxazolidinone content in the cured product, thereby enhancing its flexural strength to 71.43 MPa. This system can be effectively applied to the formulation design of room-temperature fast-curing adhesives. The room-temperature curing behavior of cyanate ester/epoxy resins in the presence of aromatic amines was comprehensively investigated by DSC and FTIR. Additionally, the curing mechanism was confirmed via PY-GC-MS. The results showed that in the reaction system, the catalyst not only promoted the formation of the triazine ring from the cyanate ester but also induced ring opening of the epoxy group. The ring-opened epoxy group then reacted with either the cyanate ester group or the intermediates containing ─C─O═NH to generate oxazolidine. Subsequently, the oxazolidine underwent a rearrangement reaction, leading to the formation of oxazolidinone. After a 5-day reaction at room temperature, the curing degree of the resin system reached 80.6%, thus accomplishing room temperature polymerization. For room-temperature fast-curing adhesive applications, this reaction system not only ensures a relatively short initial curing time but also guarantees a minimum sizing time of 60 min. When the epoxy resin content was 20%, the cured system exhibited a T d5 (5% weight loss temperature) of 323 °C, a flexural strength of 71.43 MPa, and a tensile shear strength of 8.06 MPa, with vacuum volatility meets aerospace standards.
研究领域:
高分子化学
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材料科学
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有机化学
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化学工程
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胶粘剂技术
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）