共查询到20条相似文献,搜索用时 31 毫秒
1.
Liquid‐crystalline epoxy–organoclay nanocomposites were synthesized based on two different liquid‐crystalline epoxy monomers, 4, 4′‐diglycidyloxybiphenyl (BP) and hydroquinone bis(4‐epoxypropylbenzoate) (HB). The X‐ray diffraction patterns of BP–organoclay (93A) hybrids indicate that BP diffuses into the organoclay layers and increases d‐spacing from 2.3 to 3.7 nm either in a solvent or in the melting state. The dynamic differential scanning calorimetry results indicate that the alkylammonium ion in the clay gallery catalyzes the epoxy ring‐opening reaction with a diamine curing agent. The fast intergallery polymerization forms the exfoliated nanocomposite if the content of organoclay is below 2 %. But an intercalated nanocomposite is obtained with an increase of organoclay to 10 %. The nanocomposite with 5 % of organoclay is a mixture of the two types. Polarizing optical microscopy photographs of the cured products showed that the liquid‐crystalline phase is formed with or without organoclay. Copyright © 2005 Society of Chemical Industry 相似文献
2.
The commercial epoxy prepreg SPX 8800, containing diglycidyl ether of bisphenol A, dicyanodiamide, diuron, and reinforcing glass fibers, was isothermally cured at different temperatures from 75 to 110°C and monitored via in situ near‐infrared Fourier transform spectroscopy. Two cure conditions were investigated: curing the epoxy prepreg directly (condition 1) and curing the epoxy prepreg between two glass plates (condition 2). Under both curing conditions, the epoxy group could not reach 100% conversion with curing at low temperatures (75–80°C) for 24 h. A comparison of the changes in the epoxy, primary amine, and hydroxyl groups during the curing showed that the samples cured under condition 2 had lower initial epoxy conversion rates than those cured under condition 1 and that more primary amine–epoxy addition occurred under condition 2. In addition, the activation energy under cure condition 2 (104–97 kJ/mol) was higher than that under condition 1 (93–86 kJ/mol), but a lower glass‐transition temperature of the cured samples was observed via differential scanning calorimetry. The moisture in the prepreg was assumed to account for the different reaction kinetics observed and to have led to different reaction mechanisms. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2295–2305, 2003 相似文献
3.
The effect of the molar ratio of diglycidyl ether of a bisphenol‐A based epoxy (DGEBA) and synthesized 4‐phenyl‐2,6‐bis(4‐aminophenyl)pyridine (PAP) as curing agent during nonisothermal cure reaction by the Kissinger, Ozawa, and isoconversional equations was studied. The cure mechanism was studied by FTIR analysis. Kinetic analysis of the curing reaction of DGEBA at two different concentrations (42 and 32 phr) of the curing agent was studied by using DSC analysis. With an increasing PAP content, the pre‐exponential factor increased by increasing collision probability between epoxide and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of crosslink density. The activation energies obtained from three equations were in good agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3076–3083, 2007. 相似文献
4.
5.
Thanhkieu Giang Jaeman Park Inhee Cho Youngjun Ko Jinhwan Kim 《Polymer Composites》2013,34(4):468-476
We chose two commercial epoxies, bisphenol A diglycidyl ether (DGEBA) and 3,3′,5,5′‐tetramethyl‐4,4′‐biphenol diglycidyl ether (TMBP), and synthesized one liquid crystalline epoxy (LCE), 4′4′‐bis(4‐hydroxybenzylidene)‐diaminophenylene diglycidyl ether (LCE‐DP) to investigate the effect of backbone moiety in epoxies on the thermal conductivity of epoxy/alumina composite. The DGEBA structure shows an amorphous state and the TMBP structure displays a crystal phase, whereas the LCE‐DP structure exhibits a liquid crystalline phase. The curing behaviors of them were examined employing 4,4′‐diaminodiphenylsulfone (DDS) as a curing agent. The heat of curing of epoxy resin was measured with dynamic differential scanning calorimetry (DSC). Alumina (Al2O3) of commercial source was applied as an inorganic filler. Thermal conductivity was measured by laser flash method and compared with value predicted by two theoretical models, Lewis‐Nielsen and Agari‐Uno. The results indicated that the thermal conductivity of the LCE‐DP structure was larger than that of the commercial epoxy resins such as TMBP and DGEBA and the experimental data fitted quite well in the values estimated by Agari‐Uno model. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers 相似文献
6.
The curing reaction of different mixtures of an epoxy resin (diglycidyl ether of bisphenol A type) and a phenolic resin (resole type) cured with different amine concentrations (triethylene tetramine) was studied with thermal scanning rheometry under isothermal conditions from 30 to 95°C. The gel time, defined by several criteria, was used to determine the apparent activation energy of the process. Moreover, with an empirical model used to predict the change in the complex viscosity versus time until the gel time was reached, and under the assumption of first‐order kinetics, the apparent rate constant and the apparent activation energy for the curing process were calculated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 818–824, 2005 相似文献
7.
8.
The aim of the study is to determine the optimum cure temperatures and kinetics for two different epoxy resin systems without using solvent. Two resin systems consist of EPIKOTE 828® epoxy resin–EPIKURE® 3090 polyamidoamine curing agent and DURATEK® KLM 606A epoxy resin–DURATEK® KLM 606B polyamide curing agent. The ratio of resin to curing agent was kept as 1:1 for both the systems. Curing temperatures of both the systems were determined and kinetic parameters were calculated with respect to the experimental results following nth‐order kinetics. Then, a series of isothermal temperatures was applied to the resin systems in order to assess the cure process in terms of conversion, time, and temperature by using differential scanning calorimeter (DSC). The test results of both systems show that the rate of degree of cure for EPIKOTE 828® epoxy resin–EPIKURE® 3090 polyamidoamine curing agent system is approximately 10 times higher than that of DURATEK® KLM 606A epoxy resin–DURATEK® KLM 606B polyamide curing agent system at 230°C. POLYM. COMPOS., 28:762–770, 2007. © 2007 Society of Plastics Engineers 相似文献
9.
Jun Yeob Lee 《应用聚合物科学杂志》2006,102(2):1712-1716
The effect of macroscopic orientation of liquid crystalline epoxy (LCE) resin, 4,4′‐di(2,3‐epoxypropenyloxy)phenyl benzoate, on the curing and liquid crystalline phase of LCE/diaminodiphenylester (DDE) mixture was investigated. Birefringence and curing rate of uniaxially aligned LCE/DDE on rubbed PI surface was compared with those of unaligned LCE/DDE. Anisotropic orientation accelerated the curing of LCE and facilitated the formation of liquid crystalline phase. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1712–1716, 2006 相似文献
10.
Low molar mass poly (phenylene ether) (LMW‐PPE) with phenol‐reactive chain ends was used as modifier of epoxy thermoset. The epoxy monomer was diglycidylether of bisphenol A (DGEBA), and several imidazoles were used as initiators of anionic polymerization. The curing and phase separation processes were investigated by different techniques: Differential Scanning Calorimetry, Size Exclusion Chromatography, and Light Transmission measurements. The final morphology of blends was observed by Environmental Scanning Electron Microscopy and Transmission Electron Microscopy. The epoxy network is obtained by imidazole initiated DGEBA homopolymerization. Initial LMW‐PPE/DGEBA mixtures show an UCST behavior with cloud point temperatures between 40 and 90°C. PPE phenol end‐groups can react with epoxy, leading to a better interaction between phases. The curing mechanism and phase separation process are not influenced by the chemical structure of initiators, except when reactive amine groups are present. The phase inversion is observed at 30 wt % of PPE. The mixtures with amine‐substituted imidazole present important differences in the initial miscibility and curing process interpreted in terms of fast room temperature amine‐epoxy reaction during blending. Final domain size is affected by this prereaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2678–2687, 2004 相似文献
11.
Cure behavior and kinetic study of diglycidyl ether of bisphenol A with a tertiary amine salt by differential scanning calorimetry
下载免费PDF全文
![点击此处可从《Polymer Engineering and Science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alejandra Ortiz Vélez Samuel Siles Alvarado Juan Ramón Avendaño‐Gómez 《Polymer Engineering and Science》2018,58(5):784-792
To favor the curing process of epoxy resin by cross ‐ linking and not by vitrification, the use of a tertiary amine salt is proposed. The curing reaction between diglycidyl ether of bisphenol A and tris‐(dimethylaminomethyl) phenol tri(2‐ethyl hexanoate) is studied by differential scanning calorimetry (DSC). Studies are carried out at different concentrations of amine salt: 5, 7.5, and 10 wt%. The vitrification is observed at low concentrations of the amine salt in curing experimental assessments. Furthermore, the experimental characterization of the glass transition temperature at different amine salt concentration allows inferring the polymer network connectivity. Later, the Kissinger method is used to calculate the activation energy. Finally, a reaction mechanism between the epoxy resin and the curing agent is proposed. The reaction mechanism is based on four reactions that may occur. In the most likely reaction happening in the curing, the 2‐ethyl hexanoate behaves as a catalyst through three types of esterification. The characterization and mechanism of the curing reaction of the epoxy resin DER 331 and the amine salt tris‐(dimethylaminomethyl) phenol tri(2‐ethyl hexanoate) have not been reported previously, so it is a novel support of technological relevance for the cure of epoxy community. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers 相似文献
12.
The curing characteristics of epoxy resin systems that include a biphenyl moiety were investigated according to the change of curing agents. Their curing kinetics mainly depend on the type of hardener. An autocatalytic kinetic reaction occurs in epoxy resin systems with phenol novolac hardener, regardless of the kinds of epoxy resin and the epoxy resin systems using Xylok and DCPDP (dicyclopentadiene‐type phenol resin) curing agents following an nth‐order kinetic mechanism. The kinetic parameters of all epoxy resin systems were reported in terms of a generalized kinetic equation that considered the diffusion term. The fastest reaction conversion rate among the epoxy resin systems with a phenol novolac curing agent was obtained in the EOCN‐C epoxy resin system, and for systems with Xylok and DCPDP hardeners, the highest reaction rate values were obtained in NC‐3000P and EOCN‐C epoxy resin systems, respectively. The system constants in DiBenedetto's equation of each epoxy resin system with different curing agents were obtained, and their curing characteristics can be interpreted by the curing model using a curing agent as a spacer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1942–1952, 2002 相似文献
13.
Nanocomposites of epoxy resin with montmorillonite clay were synthesized by swelling of different proportions of the clay in a diglycidyl ether of bisphenol‐A followed by in situ polymerization with aromatic diamine as a curing agent. The montmorillonite was modified with octadecylamine and made organophilic. The organoclay was found to be intercalated easily by incorporation of the epoxy precursor and the clay galleries were simultaneously expanded. However, Na‐montmorillonite clay could not be intercalated during the mixing or through the curing process. Curing temperature was found to provide a balance between the reaction rate of the epoxy precursor and the diffusion rate of the curing agent into the clay galleries. The cure kinetics were studied by differential scanning calorimetry. The exfoliation behavior of the organoclay system was investigated by X‐ray diffraction. Thermogravimetric analysis was used to determine the thermal stability, which was correlated with the ionic exchange between the organic species and the silicate layers. The morphology of the nanocomposites was evaluated by scanning electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2201–2210, 2004 相似文献
14.
Nanoscale colloidal silica showed high reactivity toward curing epoxy resins to form epoxy–silica nanocomposites under mild conditions. Adding a certain amount (5000 ppm) of magnesium chloride lowered the activation energy of the reaction from 71 to 46 kJ/mol. Less and more magnesium chloride both exhibited counter action on lowering the activation energy of the curing reaction. Tin chloride dihydrate and zinc acetylacetonate hydrate were also added into the curing compositions, however, showing no significant effect on promoting the curing reaction. Through this curing reaction, epoxy–silica nanocomposites containing high silica contents up to 70 wt % were obtained. Therefore, this reaction provided a novel and convenient route in preparation of epoxy–silica nanocomposites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1237–1245, 2005 相似文献
15.
The curing behavior of epoxy resin prepared by reacting epichlorohydrin with amine functional aniline acetaldehyde condensate (AFAAC) was investigated using AFAAC as a curing agent. The epoxy resin, {2,6‐bis‐[2‐(bis‐oxiranylmethyl‐amino)‐methylbenzyl]‐phenyl}‐bis‐oxiranylmethylamine (BPBOMA), was characterized by FTIR and 1H‐NMR spectroscopy, viscosity measurement, and determination of epoxy content. Analysis of the curing reaction was followed by differential scanning calorimetry (DSC) analysis. To investigate the curing kinetic with AFAAC, dynamic DSC scans were made at heating rates of 5, 10, 15, and 20°C/min. The activation energy and frequency factor of the AFAAC formulation were evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3168–3174, 2006 相似文献
16.
To improve the disadvantage of the low reactivity and reduce the high curing temperature of epoxy resin cured by dicyandiamide (DICY), DICY is chemically modified with phenyl hydrazine and a new curing agent, LB‐A, is developed in this research. The structure, the curing behavior, and reaction kinetics of LB‐A curing epoxy resin are investigated. Results show that the DICY is modified successfully and the well‐defined structure of DICY is destroyed after modification. Consequently, a new curing agent in a noncrystal form is resulted. Thereupon, the reactivity and compatibility between the epoxy resin and the curing agent are improved appreciably using LB‐A instead of DICY. Meanwhile, the curing temperature and activation energy of the curing reaction decrease outstanding, whereas the rate constant increases remarkably. In addition, the compressive strength and the adhesive strength in shear by tension loading of the resulting epoxy resins have been increased using LB‐A instead of DICY as the curing agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
17.
Mixtures of diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin with poly(4‐vinyl phenol) (PVPh) of various compositions were examined with a differential scanning calorimeter (DSC), using the curing agent 4,4′‐diaminodiphenylsulfone (DDS). The phase morphology of the cured epoxy blends and their curing mechanisms depended on the reactive additive, PVPh. Cured epoxy/PVPh blends exhibited network homogeneity based on a single glass transition temperature (Tg) over the whole composition range. Additionally, the morphology of these cured PVPh/epoxy blends exhibited a homogeneous network when observed by optical microscopy. Furthermore, the DDS‐cure of the epoxy blends with PVPh exhibited an autocatalytic mechanism. This was similar to the neat epoxy system, but the reaction rate of the epoxy/polymer blends exceeded that of neat epoxy. These results are mainly attributable to the chemical reactions between the epoxy and PVPh, and the regular reactions between DDS and epoxy. Polym. Eng. Sci. 45:1–10, 2005. © 2004 Society of Plastics Engineers. 相似文献
18.
Multiwall carbon nanotubes were functionalized with epoxy groups by chemical modification in four stages. At each stage, the compound was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Epoxy composite samples were prepared by mixing diglycidyl ether of bisphenol A‐based epoxy resin and synthetic epoxy‐functionalized multiwall carbon nanotube (E‐MWCNT) with different percentages (1, 3, 6, 9, 12, and 15%) in acetone. Ultrasonic dispersion was used to produce homogenous blends. The optimum ratio of the reacting components (9%) was investigated by total enthalpy of the curing reaction from differential scanning calorimetry (DSC) thermograms. The kinetics of the curing reaction for epoxy composites with 4,4′‐diaminodiphenylsolfon as a curing agent was studied by means of a DSC nonisothermal technique. The kinetic parameters such as activation energy, pre‐exponential factor, and rate constant were obtained from DSC data. The structure ofthe nanocomposites and dispersion of the E‐MWCNTs in the nanocomposites were observed using SEM, and the thermal properties were studied by thermogravimetric analysis. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers 相似文献
19.
Wei‐Jen Chen Shih‐Chieh Wang Po‐Cheng Chen Tsorng‐Wen Chen Kan‐Nan Chen 《应用聚合物科学杂志》2008,110(1):147-155
Amino‐terminated and carboxyl‐containing polyurethane (PU) is prepared by an isocyanate‐terminated PU prepolymer process. Carboxyl‐containing epoxy resin is obtained from a half‐esterification of epoxy resin with maleic anhydride. These two aqueous resins are obtained after neutralization with triethylamine and dispersion into water phase, respectively. A latent curing agent (TMPTA‐AZ) is prepared by a Michael addition of aziridine with trimethylolpropane triacrylate (TMPTA). A self‐curing system of PU/epoxy hybrid is obtained from a blending of these two aqueous resins with latent curing agent. PU/epoxy hybrid is derived from two self‐curing reactions on drying. The first curing for hybridization between PU amino groups with oxirane groups of epoxy resin is via a ring‐opening reaction and the secondary curing takes place on carboxyl groups of PU/epoxy hybrid with aziridine of TMPTA‐AZ. The final properties of these dual self‐cured PU/epoxy hybrids are reported. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
20.
Ultraviolet (UV)‐curing behavior of an epoxy acrylate resin system comprising an epoxy acrylate oligomer, a reactive diluent, and a photoinitiator was investigated by Fourier transform infrared (FTIR) spectroscopy. The conversion changes of the resin system containing 20 phr of 1,6‐hexanediol diacrylate as a reactive diluent and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one as a photoinitiator were measured under different UV‐curing conditions. The fractional conversion was calculated from the area of the absorption peak for the vinyl group vibration occurring at 810 cm?1. The effects of photoinitiator concentration, total UV dosage, one‐step or stepwise UV irradiation, UV intensity, atmosphere, and temperature on the curing behavior of the resin system were investigated. The conversion of the resin system increased rapidly at the initial stage of the UV‐curing process but increased very slowly after that. The final conversion of the resin system was mainly affected by total UV dosage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1180–1185, 2005 相似文献