Influence of the Prepolymer Type and Synthesis Parameters on Self-Healing Anticorrosion Properties of Composite Coatings Containing Isophorone Diisocyanate-Loaded Polyurethane Microcapsules.

Matic Šobak,Gregor Žitko,Nataša Čelan Korošin,Danaja Štular,Ivan Jerman,Žiga Štirn

doi:10.3390/polym13050840

Abstract

Self-healing anticorrosion composite coatings containing isophorone diisocyanate-loaded polyurethane microcapsules were developed, and comprehensive research on prepolymer and microcapsules synthesis, as well as functional composite coatings preparation and characterization, was performed. The influence of the prepolymer type and the concentration of the stabilizing agent used in the synthesis procedure on the properties of the microcapsules was studied in detail. For this purpose, three different prepolymers were prepared from toluene-2,4-diisocyanate (TDI) and either glycerol, 1,4-butanediol, or 1,6-hexanediol, and their chemical properties were investigated. Microcapsules were synthesized from the obtained prepolymers, according to the oil-in-water polymerization method, where 1,6-hexanediol was used as a chain extender, while the concentration of the stabilizing agent in the synthesis procedure was varied. Microcapsules prepared from TDI-glycerol prepolymer, synthesized in the presence of 10 wt% of the stabilizing agent, showed superior chemical, morphological, and thermo-gravimetrical properties; thus, they were incorporated into the coating in the concentration of 20 wt%. The prepared composite coatings demonstrated self-healing and anticorrosion properties, and thus the developed microcapsules show great potential for the incorporation into the composite anticorrosion coatings at critical points where damage can easily occur, providing longer and more efficient anticorrosion protection.

Highlights

According to the World Corrosion Organization, the cost of the corrosion of different metallic surfaces is estimated to be 1.3–1.4 trillion euros annually, representing 3.1–3.5%of the gross domestic product [1]
Anticorrosion self-healing composite coatings were developed with the use of isophorone diisocyanate (IPDI)-loaded polyurethane (PU) microcapsules and the influence of the prepolymer type, and the concentration of the stabilizing agent in the synthesis procedure on the self-healing anticorrosion properties of the coatings were studied
Compared to prepolymers synthesized from toluene 2,4-diisocyanate and 1,4-butanediol or

Summary

Introduction

According to the World Corrosion Organization, the cost of the corrosion of different metallic surfaces is estimated to be 1.3–1.4 trillion euros annually, representing 3.1–3.5%of the gross domestic product [1]. Polymers which are prone to scratching and can efficiently heal themselves autonomously are of great interest since they can be used for the development of materials with self-healing properties Among the latter, microcapsules show great potential for mass production, since they are easy to prepare and can be dispersed in the coating material matrix [4,5]. Encapsulated self-healing materials can be released from the microcapsules upon the mechanical damage of the coating, where they can react with a catalyst which is present in the coating, other microcapsules, or they can react with the oxygen or moisture from the environment. A film is formed, which fills the damaged area, protecting the material from water and other oxidizing species that could cause electrochemical reactions and provoke corrosion of the material [6,7,8]

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Conclusion