Self-Healing Performance of Smart Polymeric Coatings Modified with Tung Oil and Linalyl Acetate.

Aboubakr M. Abdullah,Eman Fayyad,Adnan Khan,Ramazan Kahraman,Rana Abdul Shakoor,Norhan Ashraf Ismail

doi:10.3390/polym13101609

Abstract

This work focuses on the synthesis and characterization of polymeric smart self-healing coatings. A comparison of structural, thermal, and self-healing properties of two different polymeric coatings comprising distinct self-healing agents (tung oil and linalyl acetate) is studied to elucidate the role of self-healing agents in corrosion protection. Towards this direction, urea-formaldehyde microcapsules (UFMCs) loaded with tung oil (TMMCs) and linalyl acetate (LMMCs) were synthesized using the in-situ polymerization method. The synthesis of both LMMCs and TMMCs under identical experimental conditions (900 rpm, 55 °C) has resulted in a similar average particle size range (63–125 µm). The polymeric smart self-healing coatings were developed by reinforcing a polymeric matrix separately with a fixed amount of LMMCs (3 wt.% and 5 wt.%), and TMMCs (3 wt.% and 5 wt.%) referred to as LMCOATs and TMCOATs, respectively. The development of smart coatings (LMCOATs and TMCOATs) contributes to achieving decent thermal stability up to 450 °C. Electrochemical impedance spectroscopy (EIS) analysis indicates that the corrosion resistance of smart coatings increases with increasing concentration of the microcapsules (TMMCs, LMMCs) in the epoxy matrix reaching ~1 GΩ. As a comparison, LMCOATs containing 5 wt.% LMMCs demonstrate the best stability in the barrier properties than other developed coatings and can be considered for many potential applications.

Highlights

The properties and performance of materials are strongly affected by environmental changes
It can be noticed from the globular shape that the linalyl acetate (LA) and tung oil (TO) are successfully loaded into urea-formaldehyde microcapsules
A slight rough outer surface is observed in linalyl acetate modified microcapsules (LMMCs) compared to tung oil-modified microcapsules (TMMCs) microcapsules, which enhances the mechanical interlocking of these capsules with the coating matrix

Summary

Introduction

The properties and performance of materials are strongly affected by environmental changes. The microcapsule shell can contain different types of self-healing agents such as tung oil [17], linseed oil [18], silane [19], linalyl acetate [20], or dicyclopentadiene (DCPD) [21] that has been successfully reinforced into the epoxy matrix [22]. The prepared urea-formaldehyde microcapsules were separately loaded with two different self-healing agents (tung oil and linalyl acetate) referred to as tung oil-modified microcapsules (TMMCs), and linalyl acetate modified microcapsules (LMMCs), respectively. The chemicals used in the synthesis of loaded urea-formaldehyde microcapsules includes deionized water, ethylene maleic anhydride copolymer (EMA), urea, ammonium chloride, resorcinol, 37 wt.% formaldehyde, tung oil and linalyl acetate (as self-healing agents), hydrochloric acid, and sodium hydroxide (for adjusting the pH of the urea solution), were purchased from Sigma Aldrich, Darmstadt, Germany. This corrosion test was carried out at room temperature at the frequency range of 0.01 to 100,000 Hz with an AC voltage of 10 mV

Morphological Analysis of the Synthesized Microcapsules

Thermal Stability

Particle Size Analysis

FTIR Analysis