High Throughput Screening of Mechanical Properties and Scratch Resistance of Tricomponent Polyurethane Coatings

High throughput screening (HTS) is relevant to polymer applications that require rapid screening of limited quantities of material. Polyurethane coating formulations represent one such application because multiple isocyanates or polyols are often blended to achieve specific mechanical and thermal properties. In addition, these formulations often encounter variations in curing conditions in actual use, and a rapid way to assess these variations is desirable. However, exploring the large number of possible combinations of compositions, structure, and curing conditions is experimentally challenging, especially when mechanical and durability properties are desired. We report a comprehensive screening of urethane films by using FTIR-ATR, a high throughput tensile mechanical characterization (HTMECH) apparatus, and a high throughput scratch (HTScratch) characterization method. We synthesized libraries containing three-component films composed of pure or blended polyisocyanates (1,6-hexamethylene diisocyanate or isophorone diisocyanate) and pure or blended polyols (hydroxyl-terminated polyacrylate or a modified acrylic copolymer). The HTS tools were used to explore 36 independent characterizations, performed in triplicate for each of the 57 independent sample conditions (structure, composition, and curing condition), resulting in a total of 2166 unique measurements. The HTS characterization allowed efficient identification of a small subset of systems where the toughness, strain at break, elastic modulus, and scratch resistance could be tuned by adjusting composition and disocyanate Tg. An interesting feature of the discovery is that the highly tunable systems were only identified under rapid curing conditions, and under slower curing there was less ability to tune the tensile and scratch resistance properties by adjusting composition and precursor Tg.