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additives feature | Antimicrobials and biocides


Parx Plastics’ Sanipolymer technology is being employed to make a WPC building material resistant to bacteria


have a good safety profile and can be used in high-tem- perature polymers. Microban recently introduced a next-generation SilverShield additive technology, which is one of many in the SilverShield family. “This technol- ogy provides quick-kill against bacteria, with kill speeds approaching disinfectants. The additional advantage is that by embedding these additives into the polymer, there is long-term microbial control,” explains Ong. The technology has been in development for more than three years, and Microban has conducted extensive research, particularly in food and medical applications, as well as its core consumer product area. In addition to silver, antimicrobial technologies using


copper, zinc, and quaternary ammonium salts are being considered. QTek’s new, patent-pending Surfion copper-based antimicrobial additive, for example, is a mineral powder that releases ionic copper via a diffusion mechanism to restrict reproduction of microbes on the surface of a plastic part. The additive is effective against bacteria and fungi,


Sciessent’s study of medical-grade plastics with silver-based antimicrobials included Vygon’s catheters


and is cost-effective compared to other antimicrobials, says the company. It does not affect polymer mechani- cal properties, and can be used to partially replace inorganic pigments and fillers. Surfion has been tested in several polymers, and has no processing tempera- ture limits. The additive is available as a powder and in a masterbatch form from QTek’s pilot plant. QTek is in the process of registering with the EPA and expects to soon build a commercial-size production line at its Michigan facility. Parx Plastics says its Sanipolymer technology, which is based on elemental zinc, has been demonstrated to


make a wood-plastic composite (WPC) building material resistant to bacteria. The WPC can be used, for example, to make walls for semi-permanent hospitals in disaster-relief efforts. Antimicrobial tests on the surface of the wood fibre composite were performed by the University of Ferrara, Italy, using ISO 22196 with Staphylococcus Aurus (gram+) and Escherichia Coli (E. Coli, gram-). They produced a result of 95.73% based on ISO 22196, which is defined as the difference in the logarithm of the viable cell counts found on an antibac- terial-treated product and an untreated product after inoculation with and incubation of bacteria. Gelest supplies its Biosafe HM4100 condensed silane quaternary ammonium salt as an active ingredi- ent in the form of a dry powder. It says that the additive is being used commercially in the healthcare, medical device, and food and water markets as an alternative to silver-based antimicrobials. “We are aggressively pursuing regulatory approval


for and expect to have several food and water contact products on the market within the next 12-18 months,” says Donald Wagner, technical marketing manager at Gelest, which licensed the Biosafe technology in January 2014. Time, temperature, and the presence of oxygen should be considered in processing the product. “Biosafe can break down if held at temperature for long periods of time or if temperatures exceed its thermal stability [such as in ‘post cure’ of moulded silicone parts at 400°F (200°C) in air]. On the other hand, injection moulded TPU and PA6 work well with Biosafe HM4100,” explains Wagner. Seal Shield, which is registered with the US EPA, has been producing antimicrobial products, such as waterproof keyboards, for healthcare markets since 2007 and also provides antimicrobial consulting services to product designers. In January, 2015, the company announced that its Seal Shield solution is available as a liquid, powder, or masterbatch that can be used in various


36 COMPOUNDING WORLD | July 2015 www.compoundingworld.com


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