From native starch to bio-based coatings

 
Starch can be more than just a thickener in foods or a cheap filler in materials. The lecture gives an overview of how, by means of a suitable modification, starch gets the potential to be a film former with high performance in coatings. Solid concentrations of 30-40% of starch esters with application-relevant rheological properties could be achieved using a bio-based solvent (viscosity: 102-103 mPa·s, moduli: G''>G') by optimizing the molecular weight of starch and the right choice of ester chain length (C6-C12) and degree of substitution. These starch esters exhibited excellent adhesion to a large number of substrates (e.g. aluminium, zinc, polycarbonate). Furthermore, in comparison with commercial automotive coatings and primers the starch coatings (clear coat, no additives, crosslinkers) showed comparable or even better performances in barrier (after thermal cycling) and water absorption reversibility tests. Summing up, modified starches demonstrate that bio-based materials have earned their renaissance in coating applications.