Baybond PU 403 Polyurethane polymer Bayer MaterialScience Polyurethane (PU) - Polyurethane dispersions (PUDs) >> Polyester Solvent free, polyurethane dispersion (PUD) in water. Baybond PU403 polyurethane disperson is commonly used as the film-forming component in glass fiber sizing. Glass fiber sizes based on Baybond PU 403 have excellent film-forming properties, and very good adhesion. The mechanical properties of Baybond PU 403 are improved by post-curing at 150ºC or above for 30 minutes. As with any product, Baybond PU 403 polyurethane dispersion in a given application must be tested (including but not limited to field testing) in advance by the user to determine suitability. Polyurethane dispersion. Offers very good film-forming properties and very good adhesion.