Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO

Today most of the coating formulations are based on petroleum sources, which are limited. Therefore, it is necessary to use any eco-friendly renewable source for making polymers, as they are renewable and may be non-hazardous, easily available and cheaper. In the present work we selected sorbitol as a renewable source, which is derived from naturally occurring polymer, i.e., cellulose. The technology of converting cellulose to sorbitol is well established. Hence we directly utilized sorbitol in the preparation of polyester polyols. These polyols were synthesized with the help of sorbitol, 1,2,3,6-tetrahydro phthalic anhydride, adipic acid. diethylene glycol and zinc acetate (catalyst). The synthesized polyols were characterized for their acid value, hydroxyl value, molecular weight, IR spectroscopy, etc. The polyol is further used in polyurethane coatings after reacting with polyisocyanates. For further improvement in properties, these coatings were prepared by adding nano sized ZnO. This ZnO was prepared in the laboratory and characterized for its size by SEM. The prepared PU coatings were analyzed for their coating properties such as gloss, scratch resistance, flexibility, impact test, chemical properties and anticorrosive properties. (C) 2011 Elsevier B.V. All rights reserved.