Polyurethane (coatings, sealants, adhesives)
Moisture in the PU system reacts with isocyanate, no matter in single-component or two-component polyurethane products, which produce amine and carbon dioxide, amine continue to react with isocyanate, so that its consumption to release carbon dioxide gas at the same time, form bubbles on the surface of the paint film, leading to deterioration or even the performance of the paint film failure.
2%~5% of molecular sieve (powder) in the system is sufficient to remove the residual moisture in PU system, but it’s finally depending on the moisture in the system.
In the epoxy zinc-rich primer, a trace amount of water will produce a great reaction with the zinc powder, produce hydrogen, increase the pressure in the barrel, shorten the service life of the primer, resulting in the tightness, wear resistance and hardness of the coating film. Molecular sieve (powder) as a water absorption desiccant, which is totally physical adsorption, will eliminating water and without any react with the substrate. So molecular sieve is safe and convenient for anti-corrosive coating system.
Metal powder coating
Similar reactions can occur in metal powder coatings, such as in aluminum powder coatings.