Utilisation of sebacic acid and nanohydroxyapatite in polyurethane nanocomposite coating

Abstract

The present research is focused on two-pack polyurethane (PU) coatings formulated from a polyester polyol based on renewable sebacic acid in combination with poly(ethylene glycol)-400. The purpose behind incorporating the sebacic acid was to increase the chain length. The polyester polyol was prepared by melt condensation in the presence of tosylic acid as a catalyst and characterised (acid value, Fourier transform infrared spectroscopy, gel permeation chromatography, proton (1H) nuclear magnetic resonance etc.). The prepared polyester polyol was converted to PU coatings by reacting with diphenylmethane diisocyanate. Simultaneously, to improve the physical properties of the aforesaid PU coatings, hydroxyapatite nanoparticles, which were synthesised from waste eggshells of hens’ eggs, were added in amounts of 1, 3 and 5%. The effect of nanoparticle addition on the properties of the final PU coatings such as gloss, adhesion and flexibility was studied. The dispersion of nanoparticles was observed by scanning electron microscopy, while the thermal behaviour was studied by thermogravimetric analysis and differential scanning calorimetry techniques.