Application potential of cotton seed oil as green alternative for coatings

 
Plant oils have received increased interest in manufacturing of coatings because they do not only increase the renewable content of the coatings, the flexible aliphatic structural elements of the plant oils do also result in a variation of the properties of the coatings. As the internal double bonds containing in the plant oils show low reactivity, modification of plant oils by epoxy groups, and methacrylate groups, respectively, was carried out to obtain functionalized plant oils, which are well suitable in light-mediated polymerization. Furthermore, application of cotton seed oil, instead of line seed oil, or soybean oil results in a real green alternative because cotton seed oil is outside of the food chain. Epoxidation of cotton seed oil results in quantitative conversion of the double bonds. A higher viscosity is observed for the epoxidized cotton seed oil compared to the cotton seed oil before modification. The epoxidized cotton seed oil is well suitable in light-mediated polymerization resulting in a solid transparent crosslinked polymer film. The photoinitiated cationic polymerization of epoxidized cotton seed oil is discussed in comparison with further epoxidized plant oils. Furthermore, epoxy ring opening reaction of epoxidized cotton seed oil with methacrylic acid results in methacrylated cotton seed oil. The methacrylated cotton seed oil is well suitable in photoinitiated radical polymerization resulting a solid crosslinked polymer film. Further methacrylated plant oils are included in the discussion of the photoinitiated radical polymerization as well. Moreover, contact angle measurements on the photopolymer films using a water drop show a hydrophobic surface in case of the crosslinked polymer film obtained from methacrylated cotton seed oil. In contrast to this, the contact angle of water is lower on the crosslinked polymer film made from the epoxidized cotton seed oil, and it indicates that this crosslinked polymer film surface is not hydrophobic.