A New Waterborne Acrylic Resin and Formulation Strategies for Improved Adhesion to TPO
Low surface energy substrates such as thermoplastic olefin (TPO) or ethylene propylene diene monomer (EPDM) rubber, in particular un-weathered TPO and EPDM membranes, are notoriously difficult to adhere to due to the low chemical functionality of the substrate. Typically, solvent-borne technologies (i.e., high VOC) or surface treatment of the substrate before coating has been necessary to achieve acceptable adhesion. Currently available low-VOC water-borne acrylic resins typically struggle in adhering to these new, un-weathered membranes. A newly developed water-borne acrylic resin has overcome this challenge, exceeding existing solvent-borne and water-borne options, achieving a 180° wet peel adhesion in excess of 2 pounds per linear inch (pli) with cohesive failure when formulated into a primer or basecoat. Additional formulation strategies can now be employed to optimize adhesion with the new acrylic resin, including pigment volume concentration, surfactant/dispersant level, and extender choice.