Simulation of the thermal degradation and curing kinetics of fly ash reinforced diglycidyl ether bisphenol A composite

Thermogravimetric Analysis (TGA) is concluding expanding applicability in determination of the thermal stability and degradation nature of materials. The present study investigates the thermal degradation behavior and the kinetics of degradation of epoxy mixed with varying percentages of 0, 2.5, 5, and 7.5 ​wt% fly ash. Thermal stability and degradation behavior of fly ash modified epoxy cast were determined by thermogravimetric analysis. The kinetic parameters of the EF composites were calculated by using Coats–Redfern, Broido and Horowitz–Metzger models under best-fit analysis and further proved by linear regression analysis. The kinetics of thermal degradation was calculated from data scanned at a heating rate of 10 ​°C/min. The obtained results reveal that kinetic parameters and thermal behavior of EF composites were improved with the reinforcement of fly ash. The cure kinetics of the varying content of fly ash reinforced epoxy cast were also studied by using a nonisothermal differential scanning calorimetric (DSC) technique at four different heating rates 5 ​°C/min, 10 ​°C/min, 15 ​°C/min and 20 ​°C/min. The curing kinetics of the EF composite was derived from the nonisothermal differential scanning calorimetry (DSC) data with the three Kissinger, Ozawa, and Flynn–Wall–Ozawa models, respectively.     

三元乙丙橡胶/蒙脱土纳米复合材料制备中硫化体系的比较

采用了熔融插层和两种硫化体系硫磺 促进剂和过氧化物体系制备了三元乙丙橡胶 蒙脱土纳米复合材料 ,并将这两种体系形成的纳米复合材料进行了形态、力学性能和光学性能的比较 ,同时采用Flory Rehner方程对它们的硫化行为进行了评价 .X射线衍射 (XRD)、透射电镜 (TEM)、力学性能和光学性能的测试结果表明 ,由硫磺硫化体系制备的纳米复合材料为不透明和剥离型 .其原有的d0 0 1 衍射峰消失 ,有序层被剥离成 10 0～ 2 0 0nm的片层均匀分散在EPDM基体中 ,其力学性能有了极大的提高 ;而过氧化物体系制备的纳米复合材料为半透明和插层型 .对两种体系的硫化行为的评价结果表明 ,随着有机蒙脱土加入量的增加 ,硫磺 促进剂硫化体系的t90 延长 ,交联密度减小 ,最大 最小转矩也变小 ;而过氧化物硫化体系的相应值却变化不大     

Curing of an epoxy resin modified with poly(methylmethacrylate) monitored by simultaneous dielectric/near infrared spectroscopies

Simultaneous dielectric and near infrared measurements have been performed in “real-time” to follow polymerisation reactions on blends of a diglycidyl ether of bisphenol-A epoxy resin with 4,4^′-diaminodiphenylmethane hardener and different amounts of poly(methylmethacrylate) as modifier. The effect of the modifier amount on the polymerisation reactions has been studied, as well as that of the curing temperature. Epoxy and amine conversions have been followed by near infrared spectroscopy (NIR), while changes in molecular mobility in the reaction mixture have been analysed by dielectric relaxation spectroscopy (DRS). Evolutions of ionic conductivity and α-relaxation have been analysed and vitrification times have been obtained. The relaxational behaviour has been analysed through curing in the frequency domain, being the change of the main relaxation indicative of the cure reaction advancement. DRS data are also presented as complex impedance Z(ω). Vitrification times, obtained by dielectrometry have been compared with those obtained by rheological measurements and gelation times obtained by NIR have been compared with those obtained by solvent extraction.     

Innovative energy efficient low-voltage electron beam emitters

Advanced electron beams (AEB) has developed a modular, low voltage (80–125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates.     

电子束固化环氧树脂的物理特征及其分析

分析了环氧树脂电子束辐射固化的物理特征 ,电子束辐射固化过程受活性中心扩散控制 ,整个固化区域由片层状结构组成 .与电子能量沉积分布相对应 ,环氧树脂辐射固化度的最高值是在一定深度而不是在辐射表面出现 .对电子束辐射环氧树脂体系的固化过程进行了模型解释 ,固化区域大小主要由电子的能量传递范围和浓度决定 ,反应活性中心的扩散作用影响较弱     

光聚合引发剂研究进展

对最近几年光敏聚合引发体系的研究进展进行了评述，并就一些新型光敏引发体系及引发机理进行了介绍。     

Effect of structure on thermal behaviour of epoxy resins

The paper deals with the curing behaviour of diglycidyl ether of bisphenol-A (DGEBA) using three novel multifunctional aromatic amines having phosphine oxide and amide-acid linkages. The amines were prepared by reacting tris(3-aminophenyl)phosphine oxide (TAP) with 1,2,4,5-benzenetetracarboxylic acid anhydride (P)/4,4^′-(hexafluoroisopropylidene)diphthalic acid anhydride (F)/3,3^′,4,4^′-benzophenonetetracarboxylic acid dianhydride (B). Amide-acid linkage in these amines is converted to thermally stable imide linkage during curing reaction. Curing temperatures of DGEBA were higher with phosphorylated amines than the conventional amine 4,4^′-diamino diphenyl sulphone (D). A decrease in initial decomposition temperature and higher char yields were observed when phosphorus containing amide-acid amines were used as curing agents for DGEBA.     

Effect of CTBN rubber inclusions on the curing kinetic of DGEBA-DGEBF epoxy resin

The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA-DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0-10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calorimetric and rheological analysis also evidences that gelation and vitrification times take place not punctually but in a wide range of time. Rheological data show that the presence of rubbery phase induces a higher rate of gel formation during the early stages of the reactions, confirming the calorimetric results. Finally the results are compared with theoretical models evidencing a good fitting between experimental and predictive data.     

可紫外光固化聚酰亚胺的设计制备及性能研究

以含酚羟基的2,2-双(3-氨基-4-羟基苯基)六氟丙烷(6FAP)作为接枝光敏单元的载体,以刚性苯并咪唑单元赋予材料良好的力学性能,设计合成了一种具有紫外光固化能力的可溶性聚酰亚胺.系统探究了光源距离、光源电流通量、光引发剂种类和含量、活性稀释剂种类等对固化成型过程的影响,确定了光固化聚酰亚胺的组成配方及工艺条件(光源距离为10 cm、电流通量为100%、双(2,4,6-三甲基苯甲酰基)-苯基氧化膦(Irgacure 819)含量为3 wt%、活性稀释剂1-乙烯基-2-吡咯烷酮(NVP)为20 wt%),并对光固化薄膜的基本性能进行了分析.光固化薄膜的拉伸强度达到123 MPa,固化树脂在5%(Td5)和10%(Td10)热失重时的温度分别为410和487℃,且具有较低的润湿性和吸水性.研究结果可为开发新型光敏性聚酰亚胺提供研究基础.     

环氧树脂/三乙硫醇胺固化反应行为的研究

用差热式扫描量热仪 (DSC)对双酚 A环氧 (DGEBA) 三乙硫醇胺自催化固化体系的固化反应过程进行分析 ,并根据Kissinger和Ozawa方法分别求得体系固化反应的表观活化能ΔE为 4 1.35和 4 6 .6kJ mol;根据Crane等理论计算得到该体系的固化反应级数n =0 .84及指前因子A =7.4 3× 10 3(s- 1 ) ;同时利用FTIR在位跟踪固化反应过程特征官能团吸收峰的变化 ,确定了最佳固化反应工艺条件 :T凝胶 =80℃ ,T固化 =12 0℃ ,T后处理 =16 0℃