Fatty acid derivatives as monomers in coating applications
Abstract: This work describes the physical and chemical properties ofdifferent fatty acid derivatives. Two uncommon and twoconventional fatty acids have been evaluated as monomers incrosslinking reactions.The new fatty acids examined were crepenynic acid fromCrepis alpina, containing an alkene and an alkynefunctionality, and vernolic acid from Euphorbia lagascae,containing an alkene and one epoxy group. The oxidativestability of the pure methyl esters was compared to commonfatty acid methyl esters using chemiluminescence measurements.The results show that theintroduction of epoxy or alkynegroups decreases respectively increases the oxidation rate asdetermined by chemiluminescence. In order to reveal how thefunctionality affects oxidation, model oils based on the methylesters and trimethylol propane were synthesized. The oxidativestudy of the model oils, using real-time IR andchemiluminescence, shows that an increased functionalitydecreases the amount of volatiles emitted from an oxidizingfatty acid derivative, i.e. a methyl ester emits more volatilesthan a triglyceride.An epoxy functional resin was synthesized bytransesterification of vernolic acid methyl ester onto ahyperbranched polyol and was thereafter cationicallypolymerized with different amounts of methyl vernoleate asreactive diluent. The addition of reactive diluent dramaticallylowered the initially high viscosity of the resin mixture withapproximately 50 % for each 10 wt-% diluent added, but alsoproduced much softer films than that of the pure resin.Methyl oleate and methyl linoleate were used as modelcompounds to investigate the thiol-ene coupling reaction withunsaturated fatty acid derivatives. The reactions, which werefollowed with real-time IR and NMR, showed that mercaptoacetate was more prone to add to the unsaturations of the fattyacids than mercapto propionate. The results show the importanceof choosing the right thiol and the appropriate ene in order toachieve a good system with a reasonable polymerizationrate.Chemiluminescence together with real-time IR showed to be avery powerful tool to monitor the oxidation of fatty acidderivatives, and real-time IR also for following the thiol-enecoupling reaction in model systems.
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