Chemorheology of epoxy resin Part I epoxy resin cured with tertiary amine

Epoxy resin was cured with a tertiary amine. The viscosity and dynamic mechanical properties during the curing reaction were measured by a cone-and-plate rheometer. A dual Arrhenius viscosity model was modified to predict the viscosity profile before gelation during the non-isothermal curing. The viscosity profile coincided with the experimental data. The activation energy of this system calculated using the modified model was 19.8 kcal mol^–1 for the first region, and 17.3 kcal mol^–1 for the second region. After gelation, the dynamic complex modulus was related to the reaction kinetics according to the rubber elasticity theory, and the activation energy was 15.3 kcal mol^–1. Furthermore, the gelling point can be estimated from the rheological measurements.     

Mechanical fatigue of epoxy resin

In static bending fatigue tests, epoxy resins show practically no fatigue if the stress given to specimen is lower than a critical value, which is close to the bending strength of the specimen. In cyclic bending fatigue tests, on the other hand, the resins are easily fractured even though the stresses are far below the critical values. Some strain may be accumulated on the surface of specimen through cyclic deformations. However, the strain accumulated is reversible. If the specimen is allowed to rest, the strain disappears. If the strain reaches a critical value, an irreversible transition may be induced, probably in the arrangement of segments on the surface. A crack nucleus thus created may propagate and cause the final fracture of the specimen, following the fracture mechanics of elastic materials. The lifetime of epoxy resins under cyclic bending load is determined by the time required for creating a crack nucleus on surface.     

Deformation characteristics of reinforced epoxy resin

Specimens, cut from a commercially produced epoxide resin reinforced by layers of glass cloth, were tested in tension at various strain-rates and temperatures, and at various orientations of the fibres to the tensile axis. Results are presented for elastic moduli, yield and fracture stresses, and elongations. These results give ample evidence of a decrease in the effectiveness of the reinforcement as deformation proceeds. Strain-ratechange tests show that the rate sensitivity of the composite rises rapidly as the strain increases beyond a critical value, which also indicates that the behaviour is increasingly governed by the properties of the matrix.     

环氧改性酚醛树脂的耐腐蚀性能研究

利用环氧树脂(PF)与酚醛树脂(EP)共混,再冷压-烧结成型得到改性酚醛树脂.通过在70%、50%、30%硫酸、50%盐酸、20%氢氧化钠溶液中改性酚醛树脂的腐蚀实验,证明环氧改性酚醛树脂的耐腐蚀性能优于纯酚醛,其中耐腐蚀性能最好配方是PF:EP=100:50.改性酚醛树脂耐酸性能优于耐碱性能,且在非氧化酸性(盐酸)环境中的耐腐蚀性能优于氧化性酸性(硫酸)环境下的耐腐蚀性能.热重分析(TGA)表明,环氧改性酚醛树脂的耐热性能较纯酚醛有所提高.     

Strain softening in an epoxy resin

Post-yield behaviour, particularly strain softening, has been studied here for an epoxy resin to examine the effects of postcuring and plasticization by water and a non-volatile diluent dibutylphtalate. The significance of necking was examined by conducting compression tests (at room temperature) as well as tensile tests. In the case of tensile tests, elevated temperatures were used in order to achieve yielding. The amount of strain softening was found to be reduced by postcuring or by the addition of a plasticizer. In the case of postcuring, little change in yield stress occurred, whereas, with plasticizers, a reduction in yield stress does occur.     

环氧树脂胶粘剂应用进展

阐述环氧树脂胶粘剂研究现状及应用发展。     

环氧砂浆固化剂的研究进展

环氧树脂由于具有优异的粘结、力学等性能,在建筑领域得以广泛应用。而固化剂种类以及用量对环氧树脂的固化过程、力学性质影响较大,因此固化剂的研究发展是提高环氧树脂性能的重要环节。介绍现今应用于土木工程中的传统固化剂,以及由实验室研发出的新型固化剂,并指出固化剂的发展方向。     

邻甲酚醛环氧树脂研究进展

论述了我国邻甲酚醛环氧树脂的生产、研究与应用状况及发展动向,以及与国外的差 距。介绍了邻甲酚醛环氧树脂的三种合成方法,重点论述了真空负压回流加碱生产工艺的特点。     

聚氨酯/环氧树脂IPN的研究

综述了聚氨酯 /环氧树脂的IPN生成动力学与相分离过程 ,以及形态与性能 ,并介绍了聚氨酯 /环氧树脂IPN的应用     

海因环氧树脂的制备及其应用

海因环氧树脂是由海因或其衍生物经缩水甘油化而得到的含有乙内酰脲杂环的新型特种环氧树脂,保持了环氧树脂的原有应用性能,同时乙内酰脲的杂环结构又赋予其优异的电绝缘性、耐热性、耐候性和耐磨性等特性,具有广阔的应用前景。总结了1,3-二缩水甘油基海因、缩水甘油醚类海因环氧树脂和大分子海因环氧树脂3种类型海因环氧树脂的制备方法,简要介绍了近年来关于海因环氧树脂的基本性能研究,并对其在电子封装材料、覆铜板的基板材料、绝缘材料、材料抗菌剂及其它领域的应用进行了阐述,最后探讨了海因环氧树脂在工业重防腐领域中的应用潜力。     

环氧树脂增韧改性新技术

综述了环氧树脂的增韧改性研究,着重讨论了热塑性树脂、热致液晶聚合物和互穿网络结构等环氧树脂增韧改性新技术.     

氰酸酯／双马来酰亚胺／环氧树脂三元共聚物及性能研究

采用双马来酰亚胺和环氧树脂与氰酸酯共聚对氰酸酯树脂进行改性，用FTIR跟踪了其固化过程。性能测试表明，当BCE：BMI：EP为5：2：3时，其固化物的冲击强度达到了12．2kJ·cm^-2，韧性有较大的提高；改性树脂的耐热性随着EP含量的增加而下降，当EP含量为30％时，Tg为233．7℃；改性后的氰酸酯树脂在1MHz频率下的介电常数和介电损耗角正切都比纯CE的有所增加，但上涨的幅度较小，仍具有优异的介电性能；DMA分析表明，在瓦温度时，损耗因子和损耗模量达到最大值，其中，tanδmax为0．359。     

真空辅助成型(VARI)用低黏度环氧树脂研究进展

综述了以环氧树脂为主的国内外真空辅助成型技术(VARI)用低黏度树脂基体的研发现状,以及双酚F及改性双酚F环氧树脂研究现状,分析了双酚F及改性双酚F环氧树脂应用于真空辅助成型技术(VARI)的潜力.     

Impact-modified epoxy resin with glassy second component

A resorcinol-based epoxy resin was modified by incorporating a glassy second component. The mixture showed a heterogeneous morphology with two clearly defined phases, one phase rich in oligomer, the other phase composed mainly of resorcinol epoxy resin. The fracture toughness measured asG _1c andK _1c values showed an increase from 174J m^–2 and 0.89 MN m^–1.5 S in pure epoxy resin to 431 J m^–2 and 1.36 MN m^–1.5 in 30% oligomer modified resins. The scanning electron micrographs showed that the oligomer-rich phase exhibited ductile failure behaviour and formed the dispersed phase at low concentrations while it was the continuous matrix when the concentration was 30%. Optical observations on the failure mode of thin films of the oligomer-modified epoxy resin showed the existence of both inter face failure and considerable distortion in both phase.     

Electrically conductive glass fibre reinforced epoxy resin

 The research on an industrially manufactured, electrically conductive glass fibre reinforced epoxy prepreg for aviation applications is reported. In a co-operative effort between Technical University Hamburg-Harburg (TUHH) and Daimler-Benz Aerospace Airbus (DASA) a new glass-epoxy composite with both electrical and good mechanical properties was successfully developed. The electrical conductivity was achieved adding carbon black as a conductive filler into the epoxy matrix and this at a very low level of content. The range of possible applications for this new material is not only limited to aviation. It can also be used in other transport systems or in electric and electronic devices. Received: 21 July 1998 / Accepted: 28 August 1998