The use of solvent-free, waterborne polyurethane dispersions (PUDs) is widely discussed in the literature and has grown commercially across various industries due to several environmental factors. The introduction of 1,3-Propanediol (1,3-PDO) has been found to be useful in polyurethanes as a building block component of polyester and polyether polyols, and as a chain extender. Furthermore, the use of 1,3-Propanediold has been increasingly accepted based on its use on the commercial scale for producing polyester and polyether polyols. PUDs are a desirable coating for various applications including direct-to-metal (DTM) applications since they provide very good tensile strength, wear resistance, and have good adhesion to various metal substrates.
In a previous study, 2K-PUDs were prepared using the following PDO-based polyols: PDO-Adipate 2000 polyester polyol, PDO-Sebacate 2000 polyester polyol, PO3G 2000 polyether polyols, and for reference, BDO-Adipate 2000 polyester polyol, and PTMG 2000 (Evaluation of 1,3-Propanediol-Based Polyester and Polyether Polyols in Polyurethane Water Dispersions (PUDs) for Textile Coating Applications, CPI 2018). These 2K-PUDs were evaluated as coatings on textile substrates. 2K-PUDs were based on hydroxyl-functional oligomer dispersed in water, which was crosslinked with multi-functional hydrophilic aliphatic isocyanate. Due to the crosslinking, all 2K-PUD films exhibited significantly higher tensile modulus, and improved hydrolytic and solvent resistance compared to a 1K-PUD based on PDO-Adipate 2000.