Polythiourethane microcapsules as novel self-healing systems for epoxy coatings

A novel group of microcapsule-based self-healing systems for epoxy coatings was developed. Microcapsules with polythiourethane shell wall were synthesized via interfacial polymerization from selected diisocyanates and thiols and dispersed in epoxy matrix. The obtained composites were tested for their self-healing efficiency using three-point bending test (TPBT) and scratch test. Two sets of each composite samples as well as reference (neat diglycidyl ether of bisphenol A epoxy with polyamine adduct hardener) were tested with TPBT using two methods. Standard method according to ISO 178 was applied for the first set and custom method with pre-bending with 20 N force and standard TPBT after 24 h of self-healing-for the second set. Pre-bending was applied to obtain microcracks (without sample cracking) for internal self-healing process occurrence. Scratch test allowed to evaluate self-healing efficiency at composite surface and chemical resistance of samples. FT-IR spectroscopy was conducted to confirm occurrence of self-healing process based on polyurethane secondary network forming.