02 April 2010 19:57 [Source: ICB]
New technologies for nanoscale materials are offering new properties and uses to many coatings products
Louise Cole/Northallerton, UK
MATERIALS SCIENCE has progressed so far with nanoscale materials that thin films of such products are routinely found in food packaging, the outside of drinks containers and increasingly on the outer surface of buildings and cars. One of the biggest markets for such materials, which will have its trading exchange up and running next year, is coatings.
A report on nanoscale protective coatings by global technology consultancy Future Markets says the market for nanostructured coatings was valued at $980m (€727m) in 2009. The main markets in 2009 were in construction and exterior protection (mainly in antiweathering coatings), military and defence (anticorrosion and textiles), household (easy clean and antimicrobial coatings) and automotive (anticorrosion, thermal barrier and hydrophobic).
The market for nanostructured coatings will be worth an estimated $3.5bn in 2015. The market will grow across all sectors over the next few years, [in] medical, household care and food processing markets, it adds.
"Weight and cost savings are big drivers with aircraft"
Stephen Cash, CEO, Nanocentral division, Centre for Process Innovation
These new properties can be monetized. Companies such as UK nano-insulating group Thermilate and its US competitor Industrial Nanotech produce paints that inhibit heat transfer, thereby insulating walls internally or repelling heat sources externally. Industrial Nanotech claims that its Nansulate, a patented nanocomposite insulation, is documented as the highest-quality insulation in the world. It says: "Nansulate, when fully cured, contains approximately 70% Hydro-NM-Oxide and 30% acrylic resin and performance additive. A liquid applied coating, it dries to a thin layer and provides exceptional insulation," preventing corrosion, mold and rust. "Nansulate is also low VOC and environmentally friendly." Nansulate products can be used on walls, roofs, pipes and in attic spaces. The company claims some residential customers have cut energy bills by up to 45%. Energy conservation by preventing heat loss or repelling external heat is just one of the growth markets for nanoscale-enhanced coatings.
Cash says: "By putting new properties in our materials and combining them, we can devise new functionality - for instance Pilkington glass coated with titanium dioxide, which catalyzes the dirt. If you take the particle below the wavelength of light, it does not interact with and scatter the light so it isn't opaque. Increasingly, silicon dioxide below 50nm is incorporated into polyurethane [PU] coatings to make them much harder and scratch resistant."
The automotive industry is taking advantage of scratch-free and bump-resistant coatings, and for the aviation industry, particularly the air force, nanoscale materials can offer a substantial leap in performance. "Weight and cost savings are big drivers with aircraft," says Cash. "A plane can take five tonnes of paint, so making the layer thinner saves on paint and fuel." Flatter particles to reduce drag also help.
US nanocoatings group Nanovere Technologies produces Zyvere Nanocoatings for aerospace and military uses. The company says it cannot discuss the products in detail until its global patents are filed, but they "were specifically designed to significantly reduce ice adhesion, deicing maintenance costs, and reduce the coefficient of water drag resistance, thereby decreasing the cost of jet fuel. Our line of aerospace coatings has extreme scratch resistance, chip and sand resistance, chemical and ultraviolet resistance."
A cross-link dense coating means the products are also self-cleaning. As water droplets roll across the surface, they pick up and remove dirt; at the same time the surface cuts water drag resistance by 50%.
The health care industry will also benefit from nanoscale technologies that can be harnessed in the fight against infection and superbugs. Traditionally, washing walls or coating them with pesticides has been the only defence against the spread of microbes. However, pesticides have considerable health implications for humans and they also have a relatively short life. German coatings group Bioni CS responded to customer demand and, working in collaboration with the Fraunhofer Institute for Chemical Technology, has developed antimicrobial paint containing nanosilver. Silver has long been known for its antibacterial properties and benign effect on humans. However, its use is fraught with challenges.
"You need to use the smallest possible amount," says Bioni managing director, Sven Knoll, "because even nanosilver will alter the color of the paint, making it yellow. Also, silver alone is not sufficient; fungus needs moisture to grow, so we must enhance the drying properties of the paint. You must combine the physical and chemical properties and we did extensive testing. The paint now uses less than 100ppm of nanosilver."
Bioni also uses modified nanosilver, coated to stop agglomeration and to control the availability of silver ions so they can remain in a liquid environment. Knoll says so many other fillers and additives were needed to improve the physical qualities of the paint that the company has not been able to use a standard paint formulation at all. However, the silver does away with the need for preservatives. Bioni paints will be 50% more expensive in some sectors but, in hygiene applications, often 25% lower.
He says there have been no proper field trials that would allow claims against superbugs, for instance, although tests show Bioni Hygienic paint kills 99.9% of staphylococcus aureus on the paint surface.
Bioni paints do not only have an application in hospitals. Knoll says paper manufacturers, food companies and building facades can all benefit. "The façade product has similar benefits in terms of algae and moss," he says.
Germany's Bayer Material Science has several products in its portfolio that fall into the category of "nanoscale" materials, among them the Dispercoll S product line, which consists of aqueous silicon dioxide dispersions for waterborne adhesives. It is also evaluating the addition of nanomaterials in coatings.
Bayer produces Baytubes, agglomerated carbon nanotubes, which offer a high degree of purity. The company says even small amounts are capable of imparting new properties to dispersions, plastics and other materials.
The Green Ocean Coating Heavy Duty systems by Norwegian coatings company Advanced Marine Coatings (AMC) are formulated with Baytubes, which give high abrasion resistance and save fuel. AMC's coatings also reduce maintenance costs and could replace the banned organic tin compounds that had been used to prevent organic growth on hulls.
The first ship to be coated with the system was the Berge Arzew, a 138,000m3 liquified natural gas (LNG) tanker. Extensive test coats of a Green Ocean Coating were applied to 700m2 (7,525ft2) at a thickness of 400micrometers and so far, says Bayer, the nanotubes have given a smooth pore-free surface. A spokesman says the market still has challenges ahead: "Most of the higher performance coatings systems involve the use of reactive components such as polyisocyanates. These materials usually show a high degree of incompatibility to nanoparticular substances because of their reactivity and the high surface area of the nanoparticles involved." To develop truly superior materials that show little or no incompatibility when using nanoparticles, deeper understanding of the technology is necessary, to ensure they are compatible at a molecular level, he adds.
Bayer MaterialScience opened a new pilot plant for carbon nanotubes at Chempark Leverkusen in January, 2010. The company has invested €22m ($30m) in planning, development and construction of the facility, which has an capacity of 200 tonnes/year.
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