Technical Paper Biopolymers An alternative to alkyds Novel biobased polymers for coatings applications Corresponding author: Harjoyti Kalita Mukund Sibi Metal-based catalysts have been developed to increase the Dr Bret J. Chisholm Deep Kalita Bret J. Chisholm overall rate of autoxidation. Examples of these catalysts, NDSU Center for referred to as driers, include carboxylates based on metals Nanoscale Science and Engineering High molecular weight linear polymers have been such as cobalt, manganese, iron, vanadium, lead and zirco-
[email protected] produced based on soybean oil and possessing a nium. Even with an optimised drier package, the curing rate fatty acid ester side chain in the repeat unit. The of drying oils is often undesirably long for many coating ap- unsaturation of the parent plant oil can be pre- plications. served, allowing coatings to cure by autoxidation, This problem can be at least partly attributed to the high or be converted to other functional groups to permit molecular mobility of plant oil triglycerides. This means that the use of other curing mechanisms. a substantial level of autoxidation is required to produce a film that can be touched and handled without affecting the rior to the ample supply of low cost petrochemicals, appearance or damaging the coating. To overcome this is- EUROPEAN plant oils were used extensively as binders for paints sue, alkyd resins were developed. COATINGS and coatings. The utility of plant oil triglycerides as coat- HANDBOOK P ing binders stems from the unsaturated fatty acid esters that Book tip Alkyds and their modifications outlined Brock, provide a means to crosslink the liquid plant oil into an in- Groteklaes, soluble film by simply exposing the thin film of oil to the Alkyd resins are polyester oligomers containing fatty acid es- Mischke atmosphere.