Synthesis And Properties Of Self-healing Microcapsules For Metallic Anticorrosive Coating

Corrosion of metals is the most common phenomenon in all fields of national economy,and the most effective and economical technique adopted is protective coatings. During itsservice life, the coating film undergoes changes in mechanical properties leading to formationof microcrack which subsequently propagates and exposes substrate to atmospheric moistureand oxygen. This action results in accelerated disbonding of the paint and flake formationfrom the metal coating interface. How to use the self-healing coating technology to providecorrosion protection is a cutting-edge research subject. Self-healing microcapsules are thecore technical basis of self-healing coating technology. In this work, a novel synthesis processof self-healing microcapsules and its application technology were studied, laying a solidfoundation for the development of the new self-healing coating technology in the metalcorrosion protection.Self-healing microcapsules were synthesized by in situ polymerization withurea-formaldehyde resin as shell material and tung oil as core material. The optimum processof microencapsulation was investigated by examining the effects of some reaction parameterssuch as the kind and concentration of emulsifier, rotation speed, core-shell ratio, pH value,acidification time etc on the properties of microcapsules. At the same time, the properties ofmicrocapsules such as morphology, the diameter distribution, the average diameter, chemicalstructure and thermal decomposition were characterized by optical microscope (OM), laserparticle size analyzer, fourier transform infrared (FTIR) and thermogravimetric analyzer(TGA), respectively. The results showed that the microcapsules were of smooth surface, gooddispersion and good thermal stability and highest encapsulation efficiency of95%in theconditions of OP-10of10%for the core, rotation speed of1500rpm, the core-shell ratio of2:1, pH value of3.00, the acidification time of90min.At the same time, the application of self-healing microcapsules was studied preliminarily.The self-healing microcapsules were incorporated in epoxy resin metallic anticorrosivecoating, and the prepared self-healing coating was coated onto surface of tinplate panels toinvestigate its corrosion resistance. The effects of core-shell ratio and amount ofmicrocapsules on the corrosion of metallic anticorrosive coating were monitored by visualinspection using digital camera. The self-healing process of coating with microcapsules wasalso evaluated. The results indicated that the coating with self-healing microcapsules prevented effectively the corrosion of the substrate. Further, the cracks were successfullyhealed when tung oil was released from ruptured microcapsules in the case of core-shell ratioof2:1, dosage of microcapsules of10%.