Synthesis and Properties of Novel Polyurethane-Urea Insulating Coatings from Hydroxyl-Terminated Prepolymers and Blocked Isocyanate Curing Agent

A novel series of one-pack solvent borne polyurethane-urea insulating coatings was prepared from hydroxyl-terminated prepolymers (HTP) and blocked isocyanate curing agent (BIC). HTP was prepared from poly z(tetramethylene ether)glycol (PTMEG) with excess amount of toluene diisocyanate (TDI) and subsequent reaction of NCO-terminated polyurethane with tris(hydroxymethyl-aminomethane) (TRIS). BIC was prepared from the reaction of trimethylol propane, TDI, and N-methyl aniline. HTP, BIC, and final products were characterized by conventional methods, and the curing condition was optimized via gel content measurements. Crosslink density of samples was determined via equilibrium swelling method, using Flory-Rehner equations. Thermal, mechanical, and electrical properties as well as the chemical resistance of prepared coatings were evaluated and compared with commercially available formulations. Effects of structural parameters on physical, electrical, mechanical, and dynamic mechanical (DMTA) properties of the polyurethane-urea coatings were investigated. The investigation of results showed superior electrical and mechanical properties of prepared green coating as a tailor-made electrical insulator for metals. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3714-3720, 2009