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22 POWDER COATING, August 2017 Nanotechnologies in powder coatings, Part I As new functionalities of nanomateri- als are being developed and commer- cialized, nanotechnologies will con- tinue to impact powder coatings. Nanoparticles are excellent candidates as reinforcing agents and as modifiers enabling other properties. Traditionally, inorganic fillers have been used to increase the mechanical proper- ties of powder coatings. However, their drawbacks are well documented and can include the increase of melt viscosity, re- duced impact resistance, or the forma- tion of undesirable defects. When dispersed in a resin, nanospheres with various morphologies, nanotubes, nanowhiskers, nanowires, and other nanomaterials will act as a reinforcing agent due to their resin-nanoparticle interfacial interactions. At the same time, due to a significantly smaller size, film transparency can be effectively controlled without any adverse effects on melt viscosity while enhancing me- chanical strength, elastic moduli, scratch resistance, and adhesion. More intriguingly, inorganic or or- ganic/inorganic hybrid nanoparticles may also lead to new functionalities of powder coatings. One example is su- p e r h y d r o p h o b i c p o r o u s s i l i c a t e nanoparticles with nanostructured surface topologies developed as a pow- der additive for hydrophobic resins. To improve dispersion and hydropho- bicity, silica nanoparticles are surface modified with hydrophobic polymers, thus facilitating not only self-cleaning properties, but also providing corro- sion inhibiting, anti-icing, and anti- fouling properties with applications in m a r i n e p a i n t s ( U S p a t e n t US20140094540A1). Coatings formulated with metallic nanoparticles, such as silver or zinc oxide, exhibit antimicrobial properties which inhibit the growth of bacteria and fungi. The uses of plasmonic metal nanoparticles, such as gold or sil- ver, to produce vibrant colors are being commercialized. Their advantages over traditional pigments are the abil- ity to obtain tunable colors by control- ling the size, shape, and aggregate for- mation as well as dichromic color ef- fects. The development of cost-effi- cient photonic pigments such as or- ganic colloidal nanoparticles is under way. Another example is the develop- ment of photoluminescent coatings by incorporating fluorescent carbon nan- o d o t s . N o t a b l y , t h e p r e s e n c e o f nanoparticles may also affect the cur- ing rates. It has also been shown that nano-calcium carbonate not only en- hances mechanical properties, but also exhibits catalytic effects on the curing reaction of polyester and epoxies (Prog. Org. Coat., 2011(71), 173). More futuristic powder coatings are on the horizon, and incorporating nano- sized sensors and devices into powder coatings that also serve as pigments will become a reality in the not-too-distant future. The use of carbon nanotubes or tin nanoparticles can improve charge capacity and electrical conductivity, which may lead to coatings with pres- sure or optical sensing capabilities. Ti- tanium dioxide nanoparticles are com- monly utilized as a white pigment that enhances mechanical and photolytic properties of coatings. Their photocat- alytic activities under UV irradiation capable of decomposing pollutants, toxins, or bacteria should not be ne- glected, but has rarely been explored. On the other hand, self-healing coat- ings can be produced by incorporating superparamagnetic γ-Fe2O3 iron oxide nanoparticles, whereby external oscillating magnetic fields will generate heat to repair mechanical damages (Adv. Mater., 2009(28), 5011). Critical to achieving these properties is the con- trolled dispersion of nanoparticles within a resin, and aggregated nanopar- ticles may lead to adverse effects on me- chanical and optical properties. In the second part of this article on nan- otechnologies in powder coatings, methodologies for improving disper- sions and controlling polymer-nanopar- ticle interactions will be addressed. PC Editor's note For further reading, visit Powder Coat- ing magazine's website at www.pcoat ing.com and search the Article Archive by keyword, subject, organization, author, or issue date. All articles listed in the archive are available for free download to registered users. Marek W. Urban is J.E. Sirrine Foundation en- dowed chair and profes- sor in the Department of Materials Science and Engineering at Clemson University, 299 A Sirrine Hall, Clemson, S C 2 9 6 3 4 ; 8 6 4 / 6 5 6 - 1 1 5 5 ; mareku@clemson.edu. Until 2012, he was a professor of polymer science and engineer- ing in the School of Polymers and High Per- formance Materials at the University of Southern Mississippi-Hattiesburg (USM). After 13 years at North Dakota State Uni- versity, he joined USM where he established and directed the National Science Founda- tion Materials Research Science Engineer- ing Center (MRSEC) on Stimuli-Respon- sive Polymeric Films and Coatings. He is co-director of the formally National Science Foundation Cooperative Research Center in Coatings and recently renamed Inter- face. He received an MS in chemistry from Marek W. Urban, Ph.D. Clemson University Ying Yang, Ph.D. Clemson University Powder Coatings Clinic