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Durability of Polyester and Aramid Yarns in Aqueous Solutions
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Abdul Latif A.H. MERII
|
Univ. |
London |
Spec. |
Civil Engineering |
Deg./Ph.D. |
Year 1992 |
# Pages/191 |
Aramid and polyester fibers are used in manufacturing parallel‑lay ropes and strips for use in a variety of Civil and Structural applications, such as prestressed tendons for concrete and soil reinforcement ties. As such, there is a need to know the durability of these materials in a service environment over long time periods.
This thesis investigates the hydrolytic degradation of two types of aramid and two types of polyester fiber. The principal parameters that control this degradation are presented. A variety of chemical tests are used to determine the effect hydrolysis on the molecular weight of the fibers. The physical tests measure the tensile strength of the fibers and detailed consideration is given to the accurate allowance for the clamping effect in the test machine.
The strength degradation and the corresponding hydrolytic chain scission of the amide linkage for the aramids, and of the ester linkage for polyesters, are considered in terms of time, temperature, stress level and pH. The rates of hydrolytic degradation at l00% relative humidity in the 20 C ‑ 85 C range are reported. Three different pH levels are considered at 70 C, and the effect of different load levels are reported at this temperature. The activation energy of the hydrolytic reaction, in water, is obtained and preliminary prediction of the lifetime of these fibers is presented.
