Nauka i Obrazovanie (Jan 2015)
A Mathematical Model of Repeated Impregnation of Porous Bodies with Solutions of Polymers
Abstract
The paper describes basic methods of impregnating porous bodies with solutions of polymers and their use to manufacture prepregs. It also describes the existing methods of manufacturing multilayer prepregs to produce aerospace coating of the spacecraft "Soyuz". It is shown that these prepregs have to meet high requirements for the content of the polymer, as compared with other composite materials, about 35 - 40% of the mass. Methods used for their manufacturing are long-term and non-controllable. The assumption is made that using the vacuum impregnation technology of a woven material will allow to accelerate the manufacturing process of these prepregs and improve their quality.In reviewing the technical literature have been found works on modeling the processes of impregnation, but they are aimed only at studying the speed of the woven material impregnation by various fluids and determining the time of impregnation. There were no models found to define prepreg parameters during the process of multiple impregnations. The aim of this work is to develop the simple mathematical model, which enables us to predict the polymer content of volatile products in the prepreg after each cycle of multiple impregnation of woven material with a solution of the polymer.To consider the vacuum impregnation method are used the prepregs based on silica and silica-nylon stitch-bonding fabric and bakelite varnish LBS-4 containing 50 - 60% of phenol resin and the solvent with minor impurities of pure phenol and water, as an example. To describe the process of vacuum impregnation of the porous work-piece is developed a mathematical description of the process of filling the porous space of the material with a varnish. It is assumed that the varnish components fill the porous space of the material in the same proportion as they are contained in the varnish.It is shown that a single impregnation cannot ensure the content of phenol resin in the prepreg over 32%, which does not meet requirements.The paper presents a developed mathematical model of repeated impregnation of silica fabrics by bakelite varnish with intermediate drying of the workpiece. Equations determining the amount of the polymer and the volatile products after each impregnation-drying cycle are derived.Results of calculations obtained by the mathematical model are given. The calculation results show that the multiple impregnations allow us to increase the polymer content in the prepreg and provide required parameters for a few cycles of impregnation. In the calculations were also considered various drying options with removal of different amounts of solvent. The calculations have shown that providing the specified parameters is possible if more than 50% of solvent contained in the prepreg after impregnation is removed.The mathematical model is part of a patented vacuum manufacturing technology of prepregs and allows us to define the parameters of the prepreg according to the content of the polymer and the volatile products at each stage of the multiple impregnation process of the porous material.
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