Cashew nut shell liquid terminated self-healable polyurethane as an effective anticorrosive coating with biodegradable attribute

Formulation of smart polyurethane (PU) using renewable resources as the raw materials with desired properties is a troublesome task. Thus, in this context, different compositions containing PUs were synthesized using few bio-derived raw materials like cashew nut shell liquid, modified polyol of dimer acid-glycerol and sunflower oil based monoglyceride along with other components like bis(hydroxyalkyl)poly(dimethylsiloxane), poly(epsilon-caprolactone)diol, 2,4/2,6-toluene diisocyanate and isophorone diisocyanate. The structure, morphology and surface characteristics of the synthesized PUs were well-characterized using Fourier transform infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance spectroscopy, scanning electron microscopy and X-ray diffraction technique. The synthesized PUs showed adequate mechanical and thermal properties along with good surface hydrophobicity (static contact angle: 112.3-121.2 degrees), excellent microwave responsive self-healing (within 72 - 89 s) and biodegradable attributes along with good corrosion resistance property (corrosion rate: 8.76 x 10(-5) mm/y). Most interestingly, this PU also sustains its anti-corrosive nature even after healing from mechanical damage and reduces the corrosion rate of a corroded mild steel plate 300 times more than the bare plate. Therefore, the studied bio-based PU has huge potential and paves a new direction in the field of smart anticorrosive material.