Spray-applied 100% volatile organic compounds free two component polyurethane coatings based on rapeseed oil polyols

Spray applied, two component, 100% volatile organic compounds-free polyurethane coatings were prepared from bio-based rapeseed oil polyols. Six polyol systems were developed using rapeseed oil polyols and different chain extenders (diethylene glycol, triethylene glycol, dipropylene glycol, N-methyl diethanolamine), defoamers, molecular sieves. Systems were formulated with and without dibuthyltin dilaurate catalyst. Then polyurethane coatings were developed by reacting polyol systems with isocyanate components with different functionalities (a polymeric methylene diphenyldiisocyanate (MDI) Voratec SD 100, MDI prepolymer Suprasec 2416, a polymeric MDI Suprasec 2651). The impact of polyol and chain extender structure and parameters on development of polyol systems was discussed. Technological parameters (gel time, tack-free time) were studied and results showed that formulations have short gel time and thus can be applied on surfaces in up-right position. Coatings showed good physical and mechanical properties that meet the requirements that are defined for V type two component polyurethane coatings in the ASTM D16 standard. Using The Fourier transform infra-red spectral analysis and Shore D hardness measurement the post-curing of polyurethane coatings was studied. Hydrolytic stability tests showed that developed coatings are suitable for application with water involved since they display water absorption <2% during 48 h. Thus the synthesized polyurethane coatings have the potential to be used as a coating for inside walls of potable water tanks. (C) 2015 Elsevier B.V. All rights reserved.