The future of coatings in the development of functional materials

Carolina Acosta, Researcher, AIMPLAS Chemical Technology Group, discusses the development of functional materials and suitable coating practises.

The use of coatings has evolved from the traditional function of surface decoration and protection to the development of formulations that provide the treated surface with additional functionalities. Functional coatings therefore open up a wide range of opportunities on the global market.

The traditional use of the coatings on surfaces such as steel and wood to provide protection capabilities against external factors that oxidate and deteriorate surfaces has developed to offer improved functionalities that include antifouling, antimicrobial, conductive, easy-cleaning, hydrophobic and superhydrophobic options, as well as photochromic and thermochromic characteristics. These are only some of the functionalities currently available.

The functionality of these coatings is generally demonstrated at the coating-environment interface and through coating/substrate interaction. Effective coating functionality and compatibility between the components of the coating and the substrate are therefore determining factors for the development of functional coatings. One of the most common strategies for improving coating properties is combining organic and inorganic agents. These blends can also be created at micro and nano scale, which involves carefully selecting solvents and dispersants, as well as defining operational parameters that allow for good dispersion.

In particular, to develop nanoscale blended coatings (the so-called “nanophase”), materials are simply introduced ex situ using blending procedures, or in situ, via sol-gel and intercalation processes. In the sol-gel method, the inorganic nanophase can be created in the formulation step or in the drying step in bottom-up strategies. In most cases, nanophase precursors are first pre-hydrolysed and then mixed with additional additives that act as binders. Other procedures involve the nanophase following top-down strategies of in situ generation[1]. Regardless, the choice of additivation and dispersion methods depends on the type of material and its interaction with the matrix. Functional coatings are thus developed to meet specific needs.

The great advantage of obtaining functional coatings using organic and inorganic nanomaterials is the wide range of functionalities they currently offer. Not only do these coatings protect the surface, but they also provide new high value-added performance levels to help address different challenges facing society.

Areas of interest where functional coatings can provide a rapid response to market needs include purification of the environment and action against extreme environmental phenomena. Action against microbiological agents has also generated a number of needs in which coatings can provide anti-biofilm, biocidal and self-cleaning functionalities. However, a more pressing challenge when dealing with coatings is being able to confirm that the use of these new materials is feasible and efficient for the development of products that respond to these needs, and that the process itself is sustainable.

To meet these challenges, AIMPLAS actively participates in research and development projects that evaluate the feasibility of including different nanomaterials in coatings to be used in the construction, mobility and health industries.

In the construction industry, the aim is to purify environments of contaminants such as formaldehyde by using improved solutions based on porous metal-organic frameworks (MOF), which help capture and degrade contaminants in closed areas. These materials are added during the formulation process of coatings applied to flooring, furniture and decorative paint so they can be used indoors and thus enhance the well-known function of titanium dioxide, which requires UV activation to exert the photocatalytic effect that degrades contaminants.

In the aeronautics and wind power industries, the use of nanomaterials with in situ and ex situ functionalization to produce hybrid materials is creating many opportunities to obtain functional coatings that prevent the formation of ice.

Finally, the use of nanomaterials with antimicrobial functionalities, as well as polyelectrolyte complexes that hold molecules with biocidal activity is of great interest in the formulation of coatings that can be applied to different surfaces in healthcare environments where bacteriostatic or bactericidal action is needed.

These developments have been made within the framework of the AMBICOAT, MAI-TAI and MOBACT projects, which aim to evaluate the efficiency and feasibility of the functionality of these new coatings.

[1] Functional Polymer Coatings. Principles, Methods and Applications. (2015) Edited by Limin Wu and J. Baghdachi. Wiley (ISBN 978-1-118-51070-4)