The effect of resin type on the sintering of freeformed maraging steel

The role of the resin type on the sintering of maraging steel with boron additions has been investigated. Two different resins were added to the steel mixture and their subsequent debinding was evaluated and sintering responses compared with that of a resin-free alloy. The two resins used, nylon and a mixture of phenolic resin and synthetic wax, possessed different debinding behaviour, with the latter causing significant carbon contamination of the parts. This caused the formation of a Ti-Mo carbide, depleting the matrix of these elements. Consequently, the microstructure consisted of the equilibrium Fe-Fe2B eutectic, as well as a Mo-rich boride. The liquid phase also appeared to contain significant amounts of carbon, which lowered the temperature at which the liquid formed, resulting in high density occurring at a much lower temperature. When nylon was used as the binder, a similar sintering response to the resin-free alloy was observed. (C) 2002 Published by Elsevier Science B.V.

Production of phenol-formaldehyde resin composites

The main objective of this work was to examlne the various stages of the production of industrial laminates based on phenol-formaldehyde resins, with a view of suggesting ways of improving the process economics and/or the physical properties of the final product. Aspects of impregnation, drying, and lamination were investigated. The resins used in all experiments were ammonia-catalysed. Work was concentrated on the lamination stage since this is a labour intensive activity. Paper-phenolic lay-ups were characterised in terms of the temperatures experienced during cure, and a shorter cure-cycle is proposed, utilising the exothermic heat produced during pressing of 25.5 mm thick lay-ups. Significant savings in production costs and improvements in some of the physical properties have been achieved. In particular, water absorption has been reduced by 43-61%. Work on the drying stage has shown that rapid heating of the wet impregnated substrate results in resin solids losses. Drying at lower temperatures by reducing the driving force leads to more resin (up to 6.5%) being retained by the prepregs and therefore more effective use of an expensive raw material. The impregnation work has indicated that residence times above 6 seconds in the varnish bath enhance the insulation resistance of the final product, possibly due to improved resin distribution and reduction in water absorption. In addition, a novel process which involves production of laminates by in situ polymerisation of the phenolic resin on the substrate has been examined. Such a process would eliminate the solvent recovery plant - a necessary stage in current industrial processes. In situ polymerisation has been shown to be chemically feasible.

Dynamic constitutive equation of GFRP obtained by Lagrange experiment

The note presents a method of constructing dynamic constitutive equations of material by means of Lagrange experiment and analysis. Tests were carried out by a light gas gun and the stress history profiles were recorded on multiple Lagrange positions. The dynamic constitutive equations were deduced from the regression of a series of data which was obtained by Lagrange analysis based upon recorded multiple stress histories. Here constitutive equations of glass fibre reinforced phenolic resin composite(GFRP) in uniaxil strain state under dynamic loading are given. The proposed equations of the material agree well with experimental results.

酚醛树酯的热解动力学模型

建立了一种利用热重峰值分析进行酚醛树酯热解动力学研究的方法,这种方法利用热重谱峰上几个特征点的数据来确定动力学参数.根据酚醛树酯热解DTG曲线的特点,把酚醛树酯的热解过程分解成三个阶段,用峰值分析法对每个反应阶段分别建模,通过三个反应阶段的叠加得到了一个酚醛树酯分阶段热解动力学模型,该模型能够很好地描述酚醛树酯的热解过程. 

酚醛树酯的热解动力学模型

建立了一种利用热重峰值分析进行酚醛树酯热解动力学研究的方法,这种方法利用热重谱峰上几个特征点的数据来确定动力学参数.根据酚醛树酯热解DTG曲线的特点,把酚醛树酯的热解过程分解成三个阶段,用峰值分析法对每个反应阶段分别建模,通过三个反应阶段的叠加得到了一个酚醛树酯分阶段热解动力学模型,该模型能够很好地描述酚醛树酯的热解过程.

激波管在酚醛树脂高温热解动力学研究中的应用

使用激波管作为加热手段,利用其加热速率快的优点,突破了传统方法在加热速率上的限制,研究了酚醛树脂在1400～1700K温度范围内的热解动力学.主要碳氢产物是甲烷、乙烯、乙炔和苯.通过对反应扩散过程的分析,考察了扩散对热解过程的影响.结果表明,实验中酚醛树脂的反应扩散过程迅速达到稳态,扩散影响可以忽略,首次获得了酚醛树脂在芳环开环热解机制下的热解速率常数.

酚醛树脂高温热解的激波管实验研究

采用激波管方法研究了酚醉树脂在温度1100K～1800K范围之间的热解过程.在激波管高温和短实验时间条件下,分析了实验样品颗粒在高温气相中的传热过程,讨论了样品颗粒达到热平衡的条件.通过色谱和质谱方法检测热解产物,获得了酚醛树脂高温热解产物分布和热解速率常数.酚醛树脂高温热解最主要的产物为水、一氧化碳、氢、乙炔和苯.温度1400 K将酚醛树脂热解分为高温和低温区,分别表现出不同的热解速率常数与温度的关系.