Synthesis of diphosphorus-based polyurethane esters and their application in flame-retardant nanoclay coatings

Abstract

This work describes the synthesis of diphosphorus-based polyurethane esters and their characterization by various methods. Polyurethane esters were synthesized from polyester polyols. To obtain polyester polyols, polyester was synthesized by the reaction of diphosphorus-based diol, maleic anhydride and phthalic anhydride followed by the reaction with various diols like ethylene glycol, diethylene glycol and propylene glycol. Synthesized polyester polyols were characterized by the chemical analysis and instrumental analysis techniques. Polyester polyols were then reacted with different isocyanates like toluene diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate to develop polyurethane esters. These polyurethane esters were mixed with organo-modified montmorillonite nanoclay which was taken in the proportion of 1, 3 and 5 wt.% and casted in a mold, and the formulations were coated on mild steel panels. Flame-retardant properties of casted films in the presence and absence of nanoclay were determined by limiting oxygen index analysis and UL-94 test methods. Various physical and mechanical properties of neat polyurethane ester and their nanoclay coatings such as pot life, drying properties, scratch hardness, pencil hardness, impact resistance, adhesion and flexibility were investigated. The chemical resistance properties of the coated panels were found out. Results of coating performances and mechanical properties are best with 3 wt.% nanoclay systems.