How to make coatings of starch better water resistant

Starch is a naturally occurring polysaccharide that is widely used as a coating material due to its film-forming and biodegradable properties. However, starch coatings are not inherently water-resistant, which can limit their applications in certain industries. Here are some ways to improve the water resistance of starch coatings:

  1. Blending with other polymers: Blending starch with other hydrophobic polymers such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), PolyvinylAcetate (PVAC), VinylAcetate-Ethylene (VAE) or polypropylene (PP) can improve the water resistance of the resulting coating.
    • VAE is available as dispersion. You can blend this in a solution with starch in water.
    • PVAC is available as D3 1K crosslinking dispersion adhesive. Adding extra Water resistance (White wood glue).
    • VAE Powder is available as dry powder. You can blend this as a dry premix with e.g. starch and fillers.
  2. Cross-linking: Cross-linking refers to the formation of covalent bonds between the starch molecules, which increases the strength and stability of the coating. This can be achieved by adding cross-linking agents such as epichlorohydrin, glutaraldehyde, or citric acid to the starch solution before coating.
  3. Chemical modifications: Starch molecules can be chemically modified to improve their water resistance. For example, hydrophobic groups can be added to the starch molecule through esterification or etherification, which makes the resulting coating more water-repellent.
  4. Nano-particle reinforcement: Incorporating nanoparticles such as silica, clay, or chitosan into the starch coating can improve its mechanical properties and water resistance.
  5. Plasticizer addition: Adding plasticizers such as glycerol or sorbitol can improve the flexibility and water resistance of the starch coating.

It is worth noting that the optimal approach for improving the water resistance of starch coatings depends on the specific application and requirements of the coating.