Résumé : |
Acrylic emulsion coatings properties can be improved with the addition of a polyurethane dispersion (PUD). Polyurethane dispersions are made by reacting di-functional polyols with di-functional isocyanates and dispersing them in water. The polyols can be polyether, polyester, polycarbonate, or even natural oil baed (linseed oil, castor oil, etc.). The isocyanates can be HDI, IPDI, or MDI. By varying the polyol and isocyanate, you get varying properties. The alternating hard and soft segments of the PUD give hardness, elasticity, and toughness. Acrylics being thermoplastic are either soft and flexible or hard and brittle. |