Polyurethanes from vegetable oils and applications: a review

Among the various polymers, polyurethanes are likely the most versatile specialty polymers. These polymers are widely used in many applications such as foams, coatings, insulations, adhesives, paints and upholstery. Similar to many polymers, polyurethanes relies on petrochemicals as raw materials for its major components. Indeed, nowadays many researches have focused to replace petroleum-based resources with renewable ones to improve polyurethanes sustainability. Polyurethanes are synthesized by polymerization reactions between isocyanates and polyols. Only a few isocyanates are commonly used in polyurethane industries, while a variety of polyols are available. Renewable materials such as vegetable oils are promising raw materials for the manufacture of polyurethane components such as polyols. Vegetable oils are triglycerides which are the esterification product of glycerol with three fatty acids. Several highly reactive sites including carbon-carbon double bond, allylic position and ester group in triglycerides and fatty acids open the opportunities for various chemical modifications for new polyol with different structures and functionalities. Different methods such as are epoxidation, ozonolysis, hydroformylation and metathesis have been widely studied to synthesise bio-polyol from vegetable oil for new polyurethanes, which depend on triglyceride and isocyanate reagents used. The incorporation of a vegetable oil moiety can enhance thermal stability and mechanical strength of polyurethanes. Similar to bio-polyol, the development of renewable resource based bio-isocyanates is also gained attention to produce entirely bio-polyurethanes. This article comprehensively reviews recent developments in the preparation of renewable resource based polyols and isocyanates for producing polyurethanes and applications.