Physical aging studies in epoxy resins. I. Kinetics of the enthalpy relaxation process in a fully cured epoxy resin

The physical aging of an epoxy resin based on diglycidyl ether of bisphenol-A cured by a hardener derived from phthalic anhydride has been studied by differential scanning calorimetry. The isothermal curing of the epoxy resin was carried out in one step at 130°C for 8 h, obtaining a fully cured resin whose glass transition was at 98.9°C. Samples were aged at temperatures between 50 and 100°C for periods of time from 15 min to a maximum of 1680 h. The extent of physical aging has been measured by the area of the endothermic peak which appears below and within the glass transition region. The enthalpy relaxation was found to increase gradually with aging time to a limiting value where structural equilibrium is reached. However, this structural equilibrium was reached experimentally only at an aging temperature of T_g-10°C. The kinetics of enthalpy relaxation was analysed in terms of the effective relaxation time τ_eff. The rate of relaxation of the system given by 1/τ_eff decreases as the system approaches equilibrium, as the enthalpy relaxation tends to its limiting value. Single phenomenological approaches were applied to enthalpy relaxation data. Assuming a separate dependence of temperature and structure on τ, three characteristic parameters of the enthalpic relaxation process were obtained (In A = ?333, E_H = 1020 kJ/mol, C = 2.1 g/J). Comparisons with experimental data show some discrepancies at aging temperatures of 50 and 60°C, where sub-T_g peaks appears. These discrepancies probably arise from the fact that the model assumes a single relaxation time. A better fit to aging data was obtained when a Williams-Watts function was applied. The values of the nonexponential parameter β were slightly dependent on temperature, and the characteristic time was found to decrease with temperature. © 1994 John Wiley & Sons, Inc.     

Effect of AlN content on the performance of brominated epoxy resin for printed circuit board substrate

Polymer matrix composites, based on brominated epoxy, a type of material widely used in printed circuit boards (PCBs), as matrix and AlN particle as filler were prepared. The influences of AlN content on the mechanical, thermal, and electrical properties of the composites were investigated by uniaxial tensile test, TMA, thermal conductivity measurement, DMA, and dielectric properties measurement. It was found that the properties of composites monotonically varied with AlN content except that maximum tensile strength and strain of composites corresponded to a filler content of 10 wt %. The results of DMA also showed the AlN reinforcement was more pronounced above T_g, and the peak area of tan δ versus T curves decreased with AlN content, which implied the damping capacity of the composite gradually decreased. The increase in T_g and decrease in damping were probably due to strong interaction between the AlN and epoxy matrix inhibiting the mobility of the epoxy chain. In addition, different theoretical models reported in the literature were used to predict the E, CTE, k, and D_k, and compared with the experimental data. Finally, suitable models were recommended in the present materials system. For the significant improvement of performance of epoxy, we can conclude that these composite materials may be promising for PCB substrate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1662–1674, 2007     

Ion exchange behaviour of polymeric zirconium cations

Summary Polymeric zirconium cations formed in weakly acid solution (pH2) are taken up strongly into macroporous cation exchange resins, while uptake into normal cation exchange resins (pore diameter about 1 nm) is low. Macroporous cation exchange resins loaded with polymeric Zr cations are shown to function as ligand exchange sorbents.

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Ionenaustauschverhalten polymerer Zirkonium-Kationen (Kurze Mitt.)

Zusammenfassung Polymere Zirkonium-Kationen, die in schwach sauren Lösungen (pH2) vorliegen, werden von makroporösen Kationenaustauschern stark aufgenommen, während bei den üblichen Kationenaustauschern (mit Porengrößen von etwa 1 nm) nur geringe Aufnahme stattfindet. Makroporöse Kationenaustauscher die mit polymeren Zr-Kationen beladen sind fungieren als Liganden-Austauschsorbentien.

     

玻璃纤维带隙间环氧胶渗流特性的试验研究

对环氧胶在含有玻璃纤维带的间隙中的渗流进行了试验研究. 通过试验确定纤维的松紧度、输胶压力、抽口真空度和输胶温度等不同参数对渗流流速的影响,为环氧胶的VPI(真空压力浸渍或浇铸)工艺提供工艺参数.     

Gas chromatography/mass spectrometry characterization of historical varnishes of ancient Italian lutes and violin

The organic constituents of historical vanishes from two ancient Italian lutes and a Stradivari violin, kept in the Musée de la musique in Paris, have been characterized using gas chromatography-mass spectrometry. Results have been compared with the chromatograms and mass spectra of recent as well as old naturally aged reference materials. The three historical varnishes analyzed have been shown to be oil varnishes, probably mixtures of linseed oil with resins. Identification of diterpenoids and triterpenoids compounds, and of the resins that may have been ingredients of the varnishes, are discussed in this paper.     

Validation of the concentration profiles obtained from the near infrared/multivariate curve resolution monitoring of reactions of epoxy resins using high performance liquid chromatography as a reference method

This paper reports the validation of the results obtained by combining near infrared spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS) and using high performance liquid chromatography as a reference method, for the model reaction of phenylglycidylether (PGE) and aniline. The results are obtained as concentration profiles over the reaction time. The trueness of the proposed method has been evaluated in terms of lack of bias. The joint test for the intercept and the slope showed that there were no significant differences between the profiles calculated spectroscopically and the ones obtained experimentally by means of the chromatographic reference method at an overall level of confidence of 5%. The uncertainty of the results was estimated by using information derived from the process of assessment of trueness. Such operational aspects as the cost and availability of instrumentation and the length and cost of the analysis were evaluated. The method proposed is a good way of monitoring the reactions of epoxy resins, and it adequately shows how the species concentration varies over time.     

氯磺化聚乙烯/聚甲基丙烯酸丁酯/环氧树脂三组分IPNs的合成与表征

采用同步-分步结合的方法合成了氯磺化聚乙烯/聚甲基丙烯酸丁酯/环氧树脂(CSM/PB-MA/EP)三组分IPNs.先用同步法合成CSM/EP二组分IPNs作为骨架网络,再将PBMA溶胀进入骨架网络中.得到三组分IPNs.网络间经两次相互缠结贯穿后,比单独用同步法或分步法合成的IPNs对网络间束缚作用大,且骨架网络与PBMA组成比较接近时,相容性较好.TEM结果表明:用分步染色方法可以观察三相间的形态变化和相区尺寸的相对大小.     

Syntheses and characterizations of thermally reworkable epoxy resins. Part I

To meet the need for reworkable epoxy resins, a series of cycloaliphatic diepoxides containing thermally cleavable carbamate linkages were synthesized and characterized. These materials were shown to undergo curing reactions with cyclic anhydride in a similar fashion as a commercial cycloaliphatic epoxide, except that the carbamate group within the diepoxides can act as the internal catalyst. Furthermore, cured samples of the formulations from these diepoxides started to decompose at lower temperatures, i.e., between 200–300°C as compared with 350°C for the cured sample of the commercial cycloaliphatic epoxide, which showed their potential to be used as reworkable underfill encapsulants in the electronic packaging area. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2991–3001, 1999