Kinetic measurements on the dissolution of oxide components of fiber-reinforced plastics show that the dissolution in aqueous media is a complex phenomenon and that changes in the nature of the controlling mechanism during the time of exposure can lead to an increase in rate. As a result, thorough understanding of the mechanisms is imperative in developing models for prediction of the long-term degradation of these composites. Thermogravimetric analysis has been found to be a promising indicator of the structural changes associated with the degradation process. Results obtained on specimens of concrete reinforcement rods made out of a E-glass/vinylester FRP material show that weight loss between 150 and 300°C is sensitively dependent on the nature of the corroding medium, the duration of exposure, and, in particular, the temperature at which the material was previously exposed. This weight loss correlates with the extent of moisture absorption. The enhanced weight loss between 150 and 300°C observed in the cases of samples previously exposed to attack by an aqueous media apparently reflects the increase in number of monomeric species as a result of the exposure. Increase in the effective area out of which monomers may volatilize as a result of the formation or propagation of microcracks, pores, or fiber-matrix interfacial gaps in the course of exposure may also contribute to enhanced weight loss of previously exposed samples between 150 and 300°C. The conclusion that the extent of weight loss at elevated temperatures is indicative of the extent of degradation is supported by chemical, infrared and NMR analysis of the evolved vapors and by determination of their molecular weight. Both the weight loss at elevated temperatures and the tensile strength show a strong dependence on temperature and a parabolic time dependence. In addition to thermogravimetric analysis, Raman spectroscopy is a highly sensitive and convenient technique of following structural changes resulting from environmental exposure. Together, the techniques explored here can provide important data for modeling of the environmental degradation process.

Subject
Water, Materials, Degradation, Glass, Dissolution, Rods, Ammonia, Fiber reinforced plastic, Material degradation, Composites, Weight loss, Tensile strength, Samples
Keywords:
fiber-reinforced plastics, degradation, prediction, thermogravimetric analysis, Raman spectroscopy, tensile strength, tensile modulus
© 1995 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1995
Association for Materials Protection and Performance (AMPP)
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