The Effect of Thermoplastic Polyurethane Addition on the Self-Healing of Polyester Primer Coating on Metal Substrate

Corrosion can be prevented by extending the coating protection against the penetration of electrolyte formed from the corrosive environment.The incorporation of Thermoplastic Polyurethane (TPU) as self-healing agent into the Unsaturated Polyester (UPR) polymer can prolong the coating properties of the composite.UPR and TPU were prepared using mechanical mixing technique at various loadings of 10%, 20% and 30% weight of TPU.The mixture was added with curing agent, coated on steel plate and was left to cur e.The coating was studied for adhesion, mechanical and corrosive properties using pencil hardness, adhesion tape and immersion tests.The incorporation of TPU regardless of weight % led to a reduction in mechanical properties from 2H grade to H grade. Nonetheless, there was an enhancement in adhesion post-healing with 20% TPU inclusion at 2B grade, indicating the 50% of healing efficiency.Result also recorded 45% of healing efficiency for corrosion rate in tafel polarization which was from 1.0768 to 0.5912 mmpy for the same TPU integration.The immersion results indicated the corrosion improved from 5G to 6G, demonstrating the recovery as supported by SEM images recorded at 58% of healing efficiency.Thus, it was concluded that 20 wt.% of loading TPU is an optimum loading percentage despite the reduction in mechanical and adhesion properties as it offers superior corrosion resistance compared to other loading percentages.