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1.
Monitoring the reaction of an aromatic diamine cure agent with epoxy by fluorescence technique was used for cure characterization of the interphase in epoxy/glass and epoxy/carbon composites. The effect of the various surface treatments was first studied by the model interphase obtained by using a quartz plate for glass or a modified quartz plate for carbon surface. Aminosilane treated quartz cured faster and showed increased cure extent, while water aging and air oxidation showed almost no effect on the cure kinetics in comparison to the untreated quartz surface. For a model carbon surface, air oxidation showed a faster reaction only at the early stage of cure. The effects of the various surface treatments on glass or carbon fiber were also studied with the actual composites made by a thin coating of epoxy-diamine melt on glass or carbon fiber bundles. Epoxy/glass fiber composite showed a similar trend as the model interphase system. In the case of epoxy/carbon fiber composite, both air oxidation and water aging treatment showed a faster cure reaction at the early stage of cure. Furthermore, air oxidation treatment for the epoxy/carbon fiber composite showed somewhat increased cure extent. The reasons for these trends have been discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1769–1775, 1997 相似文献
2.
This paper describes the application of a molecular sensor for in-situ monitoring of epoxy-diamine cure via remote sensing fiberoptic probes. A custom-built, fiberoptic fluorimeter allows on-line recording of fluorescence spectra directly from the cure environment. Cure reactions in epoxy-diamine network, such as diglycidyl ether of bisphenol A-diaminodiphenyl sulfone (DGEBA-DDS) or diglycidyl ether of butanediol-diaminodiphenyl sulfone (DGEB-DDS), have been monitored by a reactive molecular sensor, diamino azobenzene (DAA). DAA exhibits sensitive changes in UV-visible and fluorescence spectra due to the conversion of its primary amine groups to secondary and tertiary amine groups. Fluorescence intensities are correlated with extent of reaction in epoxy network and processing parameters, such as cure temperatures and time. The use of an internal reference dye for normalization of fluorescence intensities is necessary for the quantitative correlation of spectral signals with the network structure. Variables affecting the fluorescence intensity such as excitation volume, probe location, excitation intensity fluctuation, temperature, and background intensities from optical fiber can be calibrated by normalizing the signal intensities against the internal reference. Sulforhodamine 101 was found to be a satisfactory reference dye which provides stable, readable signals over temperatures up to 200°C. 相似文献
3.
对基于香草醛的可降解缩水甘油醚 (DEPVD)胺解得到生物基可降解胺(DAPVD),再与樟脑酸缩水甘油酯(DGECA)固化得到环氧树脂。采用红外光谱(FTIR)对DAPVD的结构进行了表征,并制备了树脂样条及碳纤维复合材料,通过动态机械分析(DMA)、拉伸测试、应力松弛测试、降解实验、热重分析(TGA)等手段对环氧树脂的性能进行了表征,并使用拉曼光谱验证了碳纤维的回收效果。结果表明:固化剂中含有的螺环缩醛结构赋予了环氧树脂可降解的特性,而固化反应中原位形成的β羟基叔胺结构在加工温度下可以参与动态酯交换反应,赋予了环氧树脂自修复和可重加工的功能。此外,基于环氧树脂良好的降解性能,制得的碳纤维复合材料在经过0.1M H+酸性溶液中50℃/48h处理后,高价值的碳纤维可以完全回收。 相似文献
4.
A tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) type tetrafunctional epoxy resin containing carbon powders was cured with the stoichiometric amount of a tetrafunctional curing agent, namely m-phenylenediamine (mPDA). Carbon powders were oxidised with air or nitric acid. The influence of carbon powders on curing of the resin was followed by dynamic mechanical analysis, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Gelation and vitrification times were determined as a function of the variations of dynamic properties. The evolution of viscoelastic modulus during curing of the different mixtures showed that untreated carbon powder clearly accelerated the kinetics of curing whilst oxidation of carbon powders could remove their catalysing effect. These results were confirmed by monitoring the changes in conversion of epoxy and amine groups during cure using the FTIR technique. DSC experiments also showed the influence of carbon powder as a catalyst and the loss of the catalysing effect as a consequence of chemical treatment. 相似文献
5.
The curing exotherm pattern is affected by the equivalent ratio of curing agent, boron trifluoride monoethylamine complex (BF3 · MEA), to epoxy resin. The diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) cures more slowly than the diglycidyl ether of bisphenol A (Epon 828). The glass transition temperatures (Tg's) of BF3 · MEA cured Epon 828 are increased with inceasing concentration of curing agent (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF3 · MEA (0.0450–0.1350 eq.) cured DGEBF. The activation energies for the thermal decomposition for BF3 · MEA (0.0450 eq./epoxy eq.) cured Epon 828 and DGEBF are almost equivalent 43 and 44 kcal/mol, respectively. DGEBF when added to DGEBA improves the Tg and char yield with the BF3 · MEA curing system. The Tg of both resin systems can be increased by longer post cure, whereas the char yield does not appear to change significantly. No ester group formation is found for the BF3 · MEA-cured DGEBF, although this has been previously reported for the DGEBA system. The BF3 · MEA cure at 120°C is better than at 140°C because of vaporization and degradation of the curing agent at the higher temperature. The rapid gelation of the epoxy resin may be another reason for the lower degree of cure at high temperature. 相似文献
6.
以改性酚醛胺固化的环氧树脂制成的防腐底漆,具有更好的耐水性和耐湿热性能。介绍其涂料配方及制备,并与俄罗斯航空通用防腐底漆进行了比较。 相似文献
7.
Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (Tg) of the composites is 12–14°C lower than the Tg of the unfilled epoxy resin. This Tg depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm. Tan δc tan δm decreases with increasing Hg-surface area. 相似文献
8.
Catherine A. Byrne Gary L. Hagnauer Nathan S. Schneider Robert W. Lenz 《Polymer Composites》1980,1(2):71-76
Monoepoxy phenyl glycidyl ether, curing agent p-chloroaniline, and the substituted urea type accelerator Monuron were used as a model system for studying the amine cure of epoxies. Reactions were carried out at 120°C with amine to epoxy equivalent rations of 0.25 and 1.0 Reaction mixtures were analyzed primarily by reverse phase high performance liquid chromatography. Three types of reactions occur; simple amine addition to epoxy, homopolymerization of epoxy, and epoxy polymerization involving the addition products. In the absence of accelerator the reaction involved simple addition. With the accelerator, there was competition between addition and polymerization, the balance depending on the amine to epoxy equivalent ratio. Both addition and polymerization were important for a ratio of 1, but polymerization far outweighed addition for a ratio of 0.25. 相似文献
9.
Mechanical test data are reported on lap joints and tensile test specimens which have been subjected to a defined post cure cycle. The mechanical properties exhibited an apparently systematic variation with temperature. Inspection of the resins indicated that chemical modification does not appear to occur to a significant extent below 433K. The change in the strength of the joints tensile test samples are discussed in terms of the relative importance of physical and chemical changes on the mechanical properties. It is evident that in the presence of oxygen considerable chemical modification can occur and this is observed both in terms of a change in colour of the resin and the appearance of voids. 相似文献
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The photoresponsive behavior of the glycidyloxyazobenzene (GOAB) monomer, synthesized using an improved method, is examined by UV/Vis spectroscopy. The monomer is cured with diethylenetriamine (DETA), forming a new epoxy resin. Proton NMR spectroscopy is used to monitor the completion of the curing reactions. Kinetics for reversible trans and cis isomerization in the cured system and also in the epoxy monomer are identified by UV/Vis spectroscopy during in situ irradiation with appropriate wavelengths (290–320 nm for UV and 400–500 nm for visible). The rates of recovery of the monomer from cis to trans forms are also obtained by heating and storing in the dark. Furthermore, the reactivity of the monofunctional GOAB monomer with a common amine, DETA, as a curing agent, is investigated using isothermal and dynamic heating scans in a DSC pan and by simultaneously monitoring the near‐FTIR spectra. The modified epoxy azobenzene proved to be reactive enough with DETA to form a network that can sustain temperatures of up to 200°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40770. 相似文献
13.
Catherine Jordan Jocelyne Galy Jean-Pierre Pascault Claude Mor Michel Delmotte Henri Jullien 《Polymer Engineering and Science》1995,35(3):233-239
An investigation was carried out into the effect ofa microwave cure on an epoxy prepolymer with a cycloaliphatic diamine mixture, as compared to a standard thermal cure. The microwave waveguide and process (propagation mode TE01) were adjusted to obtain large homogeneous samples. The extent of reaction, x, was measured during the microwave processing by size exclusion chromatography and differential scanning calorimetry. A good estimate of x was found using a modified DiBenedetto equation correlating x and the glass transition temperature Tg. The homogeneity of the samples was checked during the last steps of cure, showing the efficiency of the microwave processing and waveguide. The influence of the nature of the mold (metallic or dielectric) on the reaction kinetic was also investigated. Samples cured by both thermal and microwave processing were characterized by dynamic and static mechanical properties and then compared with those of fully crosslinked networks, i.e., postcured at a high temperature. 相似文献
14.
Simona Carrozzino Giovanni Levita Pierangelo Rolla Elpidio Tombari 《Polymer Engineering and Science》1990,30(6):366-373
The cure process of a BADGE (diglycidyl ether of bisphenol-A) resin (Epon 828) and ethylenediamine has been investigated by means of calorimetry and dielectrometry in the microwave region (107–1010 Hz) in the temperature range 50 to 70°C. Kinetic data from calorimetry were analyzed in detail. An overall kinetic order of 2.5 has been obtained. The time domain reflectometry (TDR) has been used to characterize pure components and their mixtures. Cure monitoring was carried out with both TDR and a cavity method at fixed frequency (9.5 × 109 Hz). A very good agreement was obtained between the reaction rate as measured by calorimetry and the rate of decrease of dielectric constants up to very high conversion. This was explained by admitting that the rates of disappearance of dielectric dipoles and of reactive species coincided. 相似文献
15.
L. Matisov-Rych
J. Rychlý J. Verdu L. Audouin A. Tcharkhtchi I. Janigova 《应用聚合物科学杂志》1994,53(10):1375-1384
Chemiluminescence from thermooxidized epoxide alone and that modified with phenyl glycidyl ethers has been investigated in isothermal and nonisothermal regime. Isothermal curves are characterized by a monotonous fall of chemiluminescence intensity from some initial value to very low levels of light emission. Nonisothermal curves show a maximum intensity at temperatures above 473 K. The luminescence intensity is influenced by both Tg and thermal stability of epoxide. The higher Tg or higher thermal stability brings about the higher intensity of light emission and vice versa. © 1994 John Wiley & Sons, Inc. 相似文献
16.
Walter X. Zukas 《应用聚合物科学杂志》1994,53(4):429-440
The cure behavior of diglycidyl ether of bisphenol A (DGEBA) type of epoxy resins with three aromatic diamines, 4,4′-diaminodiphenyl methane (DDM), 4,4′-diaminodiphenyl sulfone (44DDS), and 3,3′-diaminodiphenyl sulfone (33DDS) was studied by torsional braid analysis. For each curing agent the stoichiometry of the resin mixtures was varied from a two to one excess of amino hydrogens per epoxy group to a two to one excess of epoxy groups per amino hydrogen. Isothermal cures of the resin mixtures were carried out from 70 to 210°C (range depending on epoxy—amine mixture), followed by a temperature scan to determine the glass transition temperature (Tg). The times to the isothermal liquid-to-rubber transition were shortest for the DDM mixtures and longest for the 44DDS mixtures. The liquid-to-rubber transition times were also shortest for the amine excess mixtures when stoichiometry was varied. A relatively rapid reaction to the liquid-to-rubber transition was observed for the epoxy excess mixtures, followed by an exceedingly slow reaction process at cure temperatures well above the Tg. This slow process was only observed for epoxy excess mixtures and eventually led to significant increases in Tg. Using time—temperature shifts of the glass transition temperature vs. logarithm of time, activation energies approximately 50% higher were derived for this process compared to those derived from the liquid-to-rubber transition. The rate of this reaction was virtually independent of curing agent and was attributed to etherification taking place in the epoxy excess mixtures. © 1994 John Wiley & Sons, Inc. 相似文献
17.
Sue Ann Bidstrup Norman F. Sheppard Stephen D. Senturia 《Polymer Engineering and Science》1989,29(5):325-328
A low molecular weight epoxy resin is cured isothermally with an aromatic amine hardener, and the dielectric properties are measured as a function of the frequency, reaction time, and cure temperature. At specific stages in the cure, small samples from the reacting mixture are quenched and subsequently analyzed for the glass transition temperature and epoxy group conversion by differential scanning calorimetry. In this manner, the change In dielectric properties can be directly correlated with the network structure. The ionic conductivity is modeled as a function of the cure temperature and the cure-dependent glass transition temperature using a Williams-Landel-Ferry (WLF) relation. Combining this WLF relation with the DiBenedetto equation, a comprehensive model relating conductivity with the extent of reaction and cure temperature has been developed. 相似文献
18.
The phase structure of an amine cured, rubber-modified epoxy was characterized. The sharpness of the interface between the matrix and the dispersed phase, the volume fraction of the dispersed phase, the distribution of particle sizes, and the concentration of epoxy in the dispersed phase were determined. Scanning transmission electron microscopy coupled with energy dispersive X-ray analysis revealed that the interface width is less than 500 Å. Variation in the fraction of mobile hydrogens with temperature determined by nuclear magnetic resonance indicated that a small fraction of segments participated in mixing at the interface. Differential scanning calorimetry and nuclear magnetic resonance showed that the volume fraction of the dispersed phase equalled that predicted by assuming all of the rubber plus the epoxy monomer units bonded directly to the rubber precipitates. The distribution of particles greater than 0.1 μm in diameter was measured, and the average diameter of these particles was found to be 0.8 μm. This distribution accounted for approximately 50% of the dispersed phase. The epoxy concentration in the dispersed phase was determined using 13C nuclear magnetic resonance spectroscopy. This concentration was found to be less than that predicted if all the epoxy monomer units attached to the rubber molecules were present in the dispersed phase. 相似文献
19.
J. Y. Wang S.Y. Yang Y.L. Huang H.W. Tien W.K. Chin C.C.M. Ma W.J. Shu 《应用聚合物科学杂志》2012,124(3):2615-2624
The study synthesized a trifluoromethyl (CF3) groups with a modified epoxy resin, diglycidyl ether of bisphenol F (DGEBF), using environmental friendly methods. The epoxy resin was cured with 4,4′‐diaminodiphenyl‐methane (DDM). For comparison, this study also investigated curing of commercially available diglycidyl ether of bisphenol A (DGEBA) with the same curing agent by varying the ratios of DGEBF. The structure and physical properties of the epoxy resins were characterized to investigate the effect of injecting fluorinated groups into epoxy resin structures. Regarding the thermal behaviors of the specimens, the glass transition temperatures (Tg) of 50–160°C and the thermal decomposition temperatures of 200–350 °C at 5% weight loss (Td5%) in nitrogen decreased as amount of DGEBF increased. The different ratios of cured epoxy resins showed reduced dielectric constants (Dk) (2.03–3.80 at 1 MHz) that were lower than those of pure DGEBA epoxy resins. Reduced dielectric constant is related to high electrronegativity and large free volume of fluorine atoms. In the presence of hydrophobic CF3 groups, the epoxy resins exhibited low moisture absorption and higher contact angles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献