Comparative studies on coating materials of urotropine modified furfurylolated-tCNSL and methylolated-tCNSL thermoset for anticorrosive application: Switching towards a cleaner approach

Abstract

Urotropine (UT, 5–25 wt%) modified furfurylolated and methylolated technical Cashew Nut-Shell Liquid (tCNSL-Fur-UT, and tCNSL-Met-UT) were prepared to study the potential of greener derivatives as polymeric alternatives to petroleum products. Resins were synthesized using condensation reaction, green reactants (tCNSL, & furfural), and UT as a crosslinker. The chemical structures along with change in participating functional groups (-OH, –C=O, –NH) were established by Fourier Transform Infra-Red (FTIR) and Attenuated Total Reflectance (ATR) spectral analysis. Glass transition (Tg) and molecular changes with temperature was investigated by Differential Scanning Calorimetry (DSC). The coatings were studied for their potential to resist various corrosive chemicals (3.5% acid, 3.5% alkali, 3.5% saline and water). Thermal properties were investigated using Thermogravimetric Analysis (TGA), Differential TGA (DTG) (N2 environment), and heating in an oven. The high thermal stability of the resin (>400 °C) supports the formation of well crosslinked and stable polymeric system. Systematic “American Society for Testing and Materials” (ASTM) analysis reveals the hydrophobic (107°), flexible, glossy (98 GU) and resistance to scratch, impact as well as bending abilities of formulated films. Electrochemical Impedance Spectroscopy (EIS) studies revealed superior corrosion inhibition ability (>90%) even after 40 days of constant exposure to corrosive (NaCl solution) ions. The tCNSL-Fur-UT15 was found to have superior properties among other systems, projecting 15% UT as the optimum crosslinker. The study highlights the importance of cleaner production of materials through tCNSL (Agro waste), zero residues, and green chemistry principles. It gives a perspective of broadening the scope of tCNSL as thermally stable and mechanically robust polymeric substitute to petroleum derivatives in practical anticorrosive applications.