Green metal organic coating from recycled PETs and modified natural rubber for the automobile industry

• New elastomeric polyurethane coating can be prepared from natural rubber and PET.
• Physical performance of single layer coating was acceptable for automobile coating.
• Modified natural rubber grafted with polysiloxane enhanced corrosion protection.

Novel elastomeric polyurethane coating precursors from renewable natural rubber and waste bottle PET were prepared for metal coating applications. The elastomeric PU was synthesized from; modified natural rubber with hydroxyl functional groups (HLNR), modified NR grafted with polysiloxane (PDMS-g-LENR) and modified PETs (P-ET-PA and P-T-PA) such as a polyol/polyacid; a commercial MDI (Millionate MR-200) as an isocyanate. The physical properties such as film-thickness, gloss, hardness, adhesion (cross-cut and scratch-adhesion), impact test, Erichsen, bending and chemical resistance of the coated film were investigated by following the industry standards for automobile coatings. The properties of the coated films were influenced by the ratio of polyol/polyacid and the polyol nature. It was found that the coated film prepared from both of modified NR presented good adhesion with the metallic substrate by absence the surface treatment. Single layer of PU elastomer film prepared from both modified PETs with HLNR35 and MDI with mole ratio of 0.1:0.3:0.75 showed good physical properties following the industry standards for automobile coatings. The presence of PDMS-g-LENR in the coatings improved the thermal stability when compared to HLNR35. Furthermore, salt spray test and electrochemical impedance spectroscopy (EIS) were used to examine the corrosion behavior of the coated steel. It could be concluded that the best anticorrosive behavior was shown by the PDMS-g-LENR and P-T-PA formulas.