additives feature | Antimicrobials


Advantages of the MoO3 Technology


Anti-


technology over alternatives, according to AMiSTec Anti


Toxicity


microbial microbial strength duration


Silver (Ag+) Copper


Organic biocides TiO2 + UV light Disinfectants Antibiotics Acidic surfaces by MoO3


√√ √


√√


√ √


√ √√√


√ √ √


√ Short


Short √√√


√ Highly toxic


No effect on environment


Colour stability


Damage to matrix


Creation of resistancies


Still


System effective costs –


with sweat Cost & protein benefit load


NOK NOK NOK


√ √


√ √√ √ NOK


NOK √ √


The lack of nutrients in a biofilm results in exceed-


ingly low external metabolic activities in the bacteria, Guggenbichler says. As a consequence, microorgan- isms in a biofilm cannot be eradicated by antibiotics and disinfectants. “In addition, a biocide concentration that is 100 fold higher than needed for eradication of planktonic bacteria is necessary to eradicate sessile ones in a biofilm. So in essence, once a biofilm has developed, it can hardly be eliminated,” he explains. Plastics are particularly prone to biofilm formation – several polymers, plasticizers and additives provide direct nutrition for bacteria. The disadvantage of any silver technology is its


limited duration as silver ions have to be released from the surface, Guggenbichler points out, adding that the antimicrobial activity of silver can also be deactivated by even minute amounts of sulphur.


Organic options There are several hundred organic compounds with an anti-microbial effect, Guggenbichler notes, citing quaternary ammonium compounds (quats), isothia- zolinone derivatives, triclosan and chlorhexidine. In a recent scientific paper, Guggenbichler and


co-workers said that, “inspired by the body’s own defence mechanisms… acidic surfaces were created by incorporation of Brønsted-Lowry acids in various composite materials which proved to be a superior technology to presently available solutions.” Molybde- num trioxide, MoO3


, is suitable for eliminating bacteria


on surfaces, they said. Brønsted-Lowry acids incorporated in composite


materials are non-toxic and show excellent biocompat- ibility. They form acidic surfaces that effectively prevent adherence of microorganisms on surfaces, block proliferation and biofilm formation, and eventually result in rapid eradication of the microorganisms.


28 COMPOUNDING WORLD | July 2014 Colour change √


Colour change Polyolefins NOK √


√


√ √


√ √


Polymers NOK √


√ √


√ √


Cross-


resistancies √


Cross-


resistancies Yes √


ratio High √ √


√ √


√


High √√


Potential products for this technology include hospital furniture, floors and walls, instrument housings, door knobs, light switches, cables and catheters.


Moving away from OBPA Oxybisphenoxarsine (OBPA) biocide has been success- fully used in plastics – largely PVC and polyurethanes – for over 50 years, but its use is now in the twilight years. It is based on chemistry containing arsenic, and although when bound within a PVC article presents a very low risk, once the materials are disposed of there is now a recognised impact and risk to the environment from leaching and soil migration. Handling during processing and manufacture also presents a risk. OBPA was withdrawn from sale in the EU during January 2013, ahead of the Biocidal Products Directive (BPD). In the USA, OBPA is not banned, although the number of producers has fallen. While Dow has pulled out of the market, Troy Corporation has invested in toxic- ity studies and environmental case studies that are required to get its Micropel product re-registered. It has until 2016 to develop new test methods needed to proceed. Supply of OBPA should be plentiful at least until then. In the rest of the world, OBPA is still available. In a statement issued last August, Troy’s vice


president David Faherty said that “for those customers who wish to formulate with OBPA alternatives, Troy offers a full range of Micropel preservatives based on other actives, most notably IPBC [iodopropynylbutylcar- bamate], which provide comparable performance to OBPA in the control of fungal and pink stain growth in plastics and related materials.” Faherty cited a new product technology Micropel 1000, which is designed to impart surface anti-bacterial properties and offer comparable performance to silver, “but with better cost in use.” He said further Micropel materials are under development.


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