Smart Coatings On The Move
Two things become immediately obvious regarding this annual Smart Coatings meeting: it is indeed a meeting where highly technical research papers are presented (as opposed to commercial presentations), and it has become a true international event.
A total of 23 papers were presented over the two-and-a-half-day period, representing the United States, Sweden, China, Germany, Singapore and the UAE. Attendees came from the above-mentioned countries, plus the Netherlands, Mexico, Taiwan, Norway, Denmark and Belgium.
Attendees were from universities, coatings manufacturers (18), raw material suppliers (19), various government groups (5) and many company affiliations I did not recognize. What was somewhat surprising to me was that 15% of the attendees were from coatings manufacturers.
We need to be careful regarding these newest buzzwords: ‘smart' and ‘nanotechnology' when applied to coatings. There are many instances of these terms being misused - and in reality both descriptors are not really new to the coatings world. However, the use/misuse of the terminology has brought about a tremendous interest, infusion of energy and money, research effort and attention to both smart coatings and nanotechnology. Sometimes nanotechnology is used to make smart coatings. Undoubtedly the industry will benefit from the attention and dollars specified toward this end.
A smart coating obviously has to have some function besides being decorative and protective. A smart coating has to respond to a change in its environment and do something ‘smart' - usually this is a positive response. The challenge is to be able to do this millions of times - not just once - and to have stable properties in both directions (be reversible). Various stimuli can be chemical or physical (such as the thermochromic pigments that respond to temperature changes).
Some smart coating systems operate in only one direction. For instance, a coating may change color as it detects corrosion. Those that operate in two directions will change back and forth - they are switchable based on a momentary signal. Thermochromic pigments operate in this fashion. Some of the chemical stimuli that can be causative agents of change are: acid-base reactions, bond formation-breakage, photochemical reactions and electrochemical reactions. Physical stimuli include pH, temperature and pressure changes.
One category of smart coatings is bioactive coatings, which include: hygienic, antifouling, biodecontamination and biocatalytic coatings. This area is receiving a great deal of attention as we develop highly reactive coatings containing living cells.
Coatings can be designed to kill bacteria by releasing biocides, killing bacteria on contact or resisting the attachment of bacteria. Silver ion-containing coatings are very effective in killing a wide variety of bacteria.
The U.S. Naval research labs are developing coatings systems with the continuous ability to decontaminate a surface exposed to biological agents including spores. The coating is formulated using 1- or 2-K polyurethane for a variety of military and security applications. These self-decontaminating coatings are very successful against a wide range of biological pathogens.
Tailoring enzymes for specific purposes allows coatings additives to be bioengineered to exhibit increased activity or specificity for decontaminating chemical warfare agents. Enzyme-based additives have application for self-cleaning surfaces, mold-inhibiting surfaces and catalytic coatings for waste stream decontamination. Enzyme catalysts offer advantages over chemical catalysts as they are non-caustic, biodegradable and functional under mild conditions. This particular application was introduced in an earlier issue of PCI (Biocatalytic Coating, February, 2005).
Anti-foulant marine coatings are another area receiving a great deal of focus and research dollars. Fouling of ships by marine organisms is a serious problem for the Navy and other commercial vessels. Studies have shown that light fouling can cause a 15% increase in fuel consumption, which can increase to as much as a 45% fuel consumption increase with heavier fouling. One of the targets is to develop coating surfaces that allow for easy release of fouling organisms by minimizing the adhesion between the surface of the coating and the marine organism. Polysiloxane coatings are being examined in this regard.
Organic/inorganic nanocomposite coatings are also under a lot of investigation. These types of coatings are very useful as transparent, abrasion- and scratch-resistant coatings, and offer improved weather resistance. A number of companies are devoting significant effort to this approach.
Some of the paper titles included: Novel Antibacterial Polymers; Smart Surfaces for the Control of Bacterial Attachment and Biofilm Accumulation; Biocatalytic Coatings; Intelligent Coatings for Fire Protection of Wood; Intelligent Corrosion Protection by Conducting Polymers and Self-Decontaminating Surfaces to Neutralize Biological Pathogens.
Some of the papers that focused on nanotechnology included the following: Nanocomposite Dispersion and Innovation in Waterbased Coatings; Coatings Via Self-assembly of Smart Nanoparticles; Effects of Alumina and Silica Nanoparticles on Automotive Clear-Coat Properties; Synthesis of Acrylic Polymers Nanoparticles; Nanometer Scale Antimicrobial Fibers Based on Cationic Polyelectrolytes; and Engineering Nano-Porous Bioactive Coatings Containing Microorganisms. The longer paper titles are not included in the above.
Hopefully this brief report gives you a flavor of the types of papers and topics covered. Unfortunately we cannot print any of the papers in PCI, as they are designated for ACS publication only. PCI has reported on numerous smart coatings and nanotechnology in the past, however. Please visit our Web site, www.pcimag.com, to search the archives for these papers.
Mark your calendars for the next annual event, to be held February 21-23, 2007, in Orlando. For more information, visit www.emich.edu/public/ coatings_research.