Protective Nanocomposite Coatings

Abstract

With new processing techniques and technologies being introduced, the development of simple, effective protective coatings is a never-ending journey. Recently, layer-by-layer (LbL) assembly has been used to deposit coatings onto various substrates, and while the resultant nanostructure is necessary for certain properties such as dielectric strength, the number of processing steps required to achieve a particular property is often impractical for industrial-scale usage. On the other hand, a polymer-dense coacervate or a polyelectrolyte complex (PEC) comprised of oppositely charged polymers (and/or nanoparticles), can be deposited in just one or two steps. This dissertation focuses the development of protective coatings using PECs, coacervates, and/or LbL assembly to achieve a desired property.

Polyurethane foam (PUF) and cellulosic paper are highly flammable materials typically used for cushioning and packaging/construction, respectively. Clay-filled PECs and crosslinked-coacervates can be utilized to quickly deposit effective environmentally-benign flame retardant coatings to reduce the flammability of PUF and paper. While PECs and coacervates are ideal strategies to achieve effective flame retardant behavior in only two processing steps, the nanobrick wall structure of a platelet-based coating deposited using LbL assembly is ideal for exhibiting high gas barrier and dielectric breakdown strength due to the creation of a tortuous pathway, inhibiting oxygen and charge transport. Upon flame exposure, these polymer nanocomposite coatings can also exhibit heat shielding behavior through the formation of an insulating clay-reinforced bubble that protects the underlying substrate from further degradation.