Designing and performance evaluation of polyelectrolyte multilayered composite smart coatings

This work reports the synthesis of polyelectrolyte microcapsules and its effect on the anti-corrosion performance of polymeric coating applied on steel substrates. In situ polymerization technique was used for the synthesis of monolayered urea formaldehyde microcapsules loaded with linalyl acetate (MLMCs). These capsules can be broken upon mechanical stress, such as scratches or other forms of mechanical damage. To enhance corrosion protection, Phenylthiourea (PTU), a molecule sensitive to pH, was loaded between consecutive polyelectrolytes layers of polyethylenimine (PEI) and sulfonated polyether ether ketone (SPEEK) build on the surface of MLMCs using the layer by layer technique. This polyelectrolyte layered microcapsules (PMCs) carry linalyl acetate in its core and phenylthiourea entrapped between the outer layers. Both MLMCs and PMCs, in concentration of 6 wt%, were dispersed in the epoxy resin and the resulting formulation was used to coat steel plates. Experimental findings showed that epoxy coatings reinforced with PMCs demonstrate better thermal, self-healing and anti-corrosion properties. This improved performance can be attributed to the release of polymer healing and corrosion inhibiting species from the PMCs. The epoxy coatings modified with PMCs can serve as self healing coating for corrosion protection of steel parts used, for example, in the oil and gas industry.