Poly(hexamethylene diisocyanate) (PolyHDI) is an aliphatic compound belonging to the class of isocyanates. It is generally prepared by reacting hexamethylene diamine with phosgene.PolyHDI can be used as a compatibilizer to increase the complex viscosity of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/poly(lactic acid) biopolymer based blends. It can be used as a hardener that can be mixed with polyol resins to form polyurethane coatings with a wide range of applications like self-cleaning.