Relative reactivity of different monovalent alkalis on poly(ethylene terephthalate) geotextiles: Aqueous and alcoholic systems

Abstract

The relative rate of degradation of poly(ethylene terephthalate) geotextiles in various monovalent alkali hydroxides was studied in both aqueous and alcoholic systems. In an aqueous system, the reaction of all three alkalis on poly(ethylene terephthalate) geotextiles is restricted to the surface since tenacity loss was insignificant and no surface cracks was noticed, whereas in an alcoholic system, significant loss in tenacity occurred due to the formation of surface crack. Furthermore, the relative rate of reactivity of metal hydroxides in aqueous and alkaline media was temperature dependent. However, in equimolar concentration, at 80℃, the relative rate in an aqueous system is of the following order: LiOH > NaOH > KOH in the ratio of 1.65:1.1:1.0. Above 80℃, the reaction is reversed, as aqueous KOH reacts faster than aqueous NaOH. Two different activation energies were found for aqueous KOH at a threshold temperature of 80℃. Furthermore, in heterogeneous systems using dimethyl terephthalate, aqueous KOH was slightly faster than aqueous NaOH in the temperature range of 70–80℃. In an alcoholic system, KOH is almost 1.5 times faster than NaOH at 20℃ and at 60℃.