Polyvinyl Butyral Resin PVB-35

PVB-35 provides exceptional adhesion to bare metal (aluminum, steel, galvanized) through two mechanisms: (1) The residual hydroxyl groups (18–21 mol%) react with the phosphoric acid typically co-formulated in wash primers, generating metal phosphate bonds at the metal-coating interface — essentially an in-situ conversion coating; (2) PVB's high polarity and hydrogen-bonding capability ensure intimate substrate wetting even on marginally surface-prepared metal. Wash primers using PVB-35 achieve adhesion rating 0 (ISO 2409 crosshatch) on cold-rolled steel, with salt spray resistance >500 hours for the subsequent full paint system. The resin is dissolved in ethanol/butanol mixtures (45–55% solids) and pigmented with zinc chromate-free inhibitors (zinc phosphate, strontium chromate). PVB-35 is also the standard interlayer resin for automotive laminated windshields (1.52 mm film), providing both structural bonding and the energy-absorbing ductility required by safety regulations.