Nanocomposite coatings comprising APS-treated linseed oil-embedded polyurea-formaldehyde microcapsules and nanoclay, part 2: Self-healing and corrosion resistance properties

Abstract

In this research, polyurea-formaldehyde-based microcapsules loaded with linseed oil were synthesized by means of in-situ polymerization in an oil-in-water emulsion. The surface of the microcapsules was treated with 3-aminopropyltrimethoxy silane (APS) using sol-gel procedure at pH 7.5. SEM and optical microscopy were used to characterize un-treated and APS-treated microcapsules. The mechanical properties of epoxy-based nanocomposite coatings comprising different combinations of APS-treated microcapsules and nanoclay particles were evaluated by means of tensile strength measurements. The standard salt spray test, Electrochemical Impedance Spectroscopy (EIS) and SEM were utilized to study the corrosion resistance and healing performance of the samples in the presence of nanoclay.The results revealed improvement in tensile strength properties and anti-corrosion resistance by the simultaneous use of APS-treated microcapsules and nanoclay. This was attributed to the enhanced interactions between the polymer coating and the microcapsule shell and the barrier properties of intercalated nanoclay platelets. The natural salt spray test EIS results revealed enchasing corrosion resistance of the coating samples containing APS-treated microcapsule in comparison with neat epoxy samples during 7 days exposure to the conditions of the tests. The sample containing APS-treated microcapsules and nonoclay particles showed the best performance along with all samples. APS-treated microcapsules were more likely to rupture during the scratching, leading to better corrosion resistance and self-healing properties.