Lifetime prediction of aramid yarns applied to offshore mooring due to purely hydrolytic degradation

Abstract

The discovery of oil fields in deepwater over the last decades led the oil and gas industry to the necessity of replacing the steel wire cables of the mooring systems of offshore platforms by polymeric ropes. These systems must be designed to work for at least 20 years without showing substantial loss in tensile strength or in their mechanical behavior along this period. However, some polymers present degradation by seawater through the process of hydrolysis, and the question whether it affects significantly the materials’ ultimate tensile strength arises. Accelerated hydrolysis tests were conducted in yarn samples of aramid at high temperature in order to use the Arrhenius correlation to predict their lifetime under service conditions. In order to decouple the total degradation into a thermal and a purely hydrolytic part, separate aging experiments were performed into a dry chamber and the conclusion was that thermal degradation does not play a significant role in the total degradation of aramid due to the water submersion at the temperatures tested.