Nanostructured, Nonuniform and Core-Shell Polyurethane Dispersions
Waterborne polyurethane dispersions (PUDs) are a maturing technology, with several suppliers offering a diversity of commercial products for a wide spectrum of applications. Due to their superior properties, ease of use and "green" nature, PUDs are often materials of choice by many coatings manufacturers. Common processes for making these dispersions do not offer easy ways of controlling particle morphology, which puts PUDs at a disadvantage to structured acrylic emulsions. The latter are discussed briefly in the following section.
A similar approach is used to make polyurethane-acrylic hybrids as described in U.S. Patent Nos. 4,644,0303 and 5,137,961.4 In essence, instead of one of the acrylic stages, a polyurethane is used.