Relationship between Properties of Epoxy Resins to Coat Water Pipes and Elution of Amines Curing the Resins into Service Water

Abstract

Water tanks and water pipes are now coated with epoxy resins to avoid rusty water in water service. It is the aim of this work to investigate the relationship between amines used as curing agents and their elution into service water. Epoxy monomer used in this experiment is Epikote-828 (a diglycidyl ether of bisphenol A) and four types of amines are ethylenediamine (EDA), diethylenetriamine (DTA), isophoronediamine (IPD) and m-xylylenediamine (XDA). The amount of amines eluted into service water was determined by measuring consumption of potassium permanganate. Ratio of the monomer reacted was determined by measuring the amount of residual epoxy groups, using FT-IR spectrometry. The elution of amines into service water decreased in the order: DTA > EDA > IPD > XDA. Diffusion coefficients of water in epoxy resins were dependent on the amines and decreased in the same order. The amount of the residual epoxy groups in the resins varies with the amines and decreased in the reverse order. It is pointed out that the diffusion coefficient of water in the resin and amine elution into service water is small when the ratio of the monomer reacted with the amines is large.