Paint & Coatings Industry - November 2008 - (Page 48)

Novel, UV-Curable Nanotechnology-Enabled Coatings FIGURE 3 | Mold formation on uncoated paper (left) and coated paper (right) not showing mold formation. FIGURE 4 | Aluminum tanks (with stainless steel tubing and other steel parts). Moreover, the particle size apparently yields a substantial increase in the diffusion path and the concomitant barrier properties of the film. Specifically, coatings using this formulation approach have demonstrated superior adhesion and moisture barrier capability as compared to many conventional coatings. Unique Barrier Properties2 Substantial barrier properties have been created by the use of nano-particles in formulations containing monomers with a variety of shapes, functional groups and polarities. An assortment of these ring shapes, aliphatic and aromatic, may be combined to fill space in interesting ways. Space filling by nano-particles also appears to be a key contributor. In some cases, especially when optical clarity is not required, micron sized and submicron sized particles may be used as well. The coating application dosage (weight or thickness) may also be varied to produce a range of barrier effects. Products using the preceding formulation concept for creating a barrier in paper show many of these effects. For example, a more polar, hydrophilic component promotes writeability. Some forms of this coating also contain larger pigment particles. The data in Table 1 illustrates the effects that may TABLE 1 | Air permeance by Gurley apparatus; oxygen and water transmission by Macon apparatus. Coated Samples 1 2 3 4 5 Time to Pass Air Permeance 100 ml air (cm3/m2 d atm) (sec) Too dense 12 19 45 Too dense n/a 7669 4848 2026 n/a Oxygen Transmission (cm3/m2 d atm) 943.8 Water Transmission (g/m2 d) 177.7 232.8 302.4 Uncoated Samples 3 samples 46 2 46015 be produced by different dosages. The paper substrate used was qualitative laboratory filter paper. Samples were produced by draw down. The “time to pass 100 ml of air” is believed to be a surrogate for relative coating thickness, and as such the air permeance data show a decrease in rate with longer “time to pass 100 ml of air” times. Moreover, the air permeance is lowered by the coating from 6 to 200 times, presumably depending on thickness. Oxygen transmission values for Samples 1 and 5 were described to be between high-density polyethylene (HDPE) and polyethyleneterephthalate (PETP), and might be expected to be improved with improved coating conditions for film thickness and uniformity. Water vapor transmission is very low for Samples 1 and 5, and also would be expected to improve with optimized coating conditions. An application with great potential human value has been supported by recent tests for mold resistance.3 Based on a simple test at our laboratory it was observed that mold growth on coated paper was retarded for a number of formula variations (Figure 3). Many types of mold will grow on wet paper such as gypsum board. To a large extent, this is a cosmetic problem, causing staining and unpleasant odors. However, there is a mold, Stachybotrys chartarum, whose appearance is actively dangerous. Biologically active compounds produced by this fungus can be a threat to human health. ASTM D 3273 is a standard test protocol for testing mold resistance on drywall. However, this protocol does not test for the growth of S. chartarum. A test protocol for the growth of S. chartarum has been developed at a major research university. Consequently, samples were submitted to the university to determine the general resistance of coated drywall samples to the growth of S. chartarum. All prepared samples as well as a set of uncoated controls were autoclaved to eliminate NOV EMBER 2008 | W W W . P C I M A G . C O M http://WWW.PCIMAG.COM

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Paint and Coatings Industry - November 2008 Contents Viewpoint Industry News Calendar of Events Company News Mergers and Acquisitions Names in the News HiTone Resins for Enhanced Pigment Affinity of Powder Coatings New Water-Based Interior Coatings Combine Innovation and Quality With Respect for the Environment Novel, UV-Curable Nanotechnology-Enabled Coatings Highly Weather-Resistant Radiation-Curable Monomers and Oligomers for Exterior Applications Konica Minolta — Sensing Success for Viracon Self-Crosslinkable Thermosetting Acrylics for Use in Water-Dilutable Coatings Paint and Criminal Forensic Science Supplier and Application/Curing Showcases Materials Watch Classifieds Advertiser Index

Paint & Coatings Industry - November 2008

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