Water Uptake in Epoxy Ionic Liquid Free Film Polymer by Gravimetric Analysis and Comparison with Nondestructive Dielectric Analysis.

Lucas Ollivier-Lamarque,Sébastien Livi,Tetsuya Uchimoto,Nicolas Mary

doi:10.3390/nano12040651

Abstract

Due to their high surface coverage, good adhesion to metal surfaces, and their excellent corrosion resistance, epoxy thermosets are widely used as protective coatings. However, anticorrosion protection of these coatings can be improved against water uptake and can be tuned by changing the chemical nature of the curing agents. In this work, a comparative study has been performed on the water uptake of an epoxy–amine based on bisphenol A diglycidyl ether (DGEBA) cured with an aliphatic amine and the same epoxy initiated with a phosphonium ionic liquid (IL). Thus, the epoxy networks were immersed in saline water solution in a controlled temperature environment. Gravimetric and electric impedance measurements were carried out for a maximum of 3 months. Results were analyzed in order to assess the water diffusion coefficients and water saturation limits. Two models, the Brasher–Kingsbury and a novel mixing rule, were applied on permittivity values. Results highlighted that epoxy–ionic liquid systems are less sensitive to water uptake than conventional epoxy–amine networks. Due to their higher hydrophobic properties the water diffusion coefficient of epoxy–ionic liquid systems are two times less compared to epoxy–amine samples and the water saturation limit is more than four times less. The analysis also shows that the novel mixing rule model proposed here is prone to better estimate the water uptake with accuracy from electrical impedance measurements.

Highlights

Corrosion reduces structures’ and components’ life span in the transportation, energy, utilities, and civil engineering domains
Due to their higher hydrophobic properties the water diffusion coefficient of epoxy–ionic liquid systems are two times less compared to epoxy–amine samples and the water saturation limit is more than four times less
The analysis shows that the novel mixing rule model proposed here is prone to better estimate the water uptake with accuracy from electrical impedance measurements

Summary

Introduction

Corrosion reduces structures’ and components’ life span in the transportation, energy, utilities, and civil engineering domains. Several strategies, such as structural transformations and surface treatments, can be applied to prevent degradation. Metallic or organic coatings are other available solutions. These latter act as physical barriers between the substrate and the environment. Organic coatings present good strength-to-weight ratio; they are easy to apply and cost-efficient [1,2,3]. Epoxy prepolymers are widely used for anticorrosion protection due to their high surface coverage, good adhesion to metal surfaces and chemical properties, especially their excellent corrosion resistance. The pinhole porosity of epoxy coatings is well-known

Methods

Results

Conclusion