Antimicrobial Efficacy and Additive Performance

How are antimicrobial products tested?

All our antimicrobial testing is carried out by independent laboratories, mostly in the UK. 

We employ a variety of test methods, dependent on the material being tested, the end application and the organisms against which efficacy needs to be determined…

ISO 22196:2011… Antibacterial activity of non-porous surfaces. Probably the most widely used method for evaluating antibacterial activity of injection moulded or extruded polymers, cast resins or permanent coatings. 

The most frequently tested organisms are Staphylococcus aureus and E. coli, although we often test against other bacteria including strains of Salmonella, Pseudomonas, Listeria, Streptococcus and Legionella.

ISO 21702:2019… Anti-viral activity of non-porous surfaces. This was a relatively uncommon test until the COVID-19 (SARS-CoV-2) epidemic but is now, understandably, in very high demand.

SARS-CoV-2 testing is only available from a very limited number of laboratories and is notably more expensive than for most viruses. For this reason, the majority of laboratories offer testing against ‘surrogate’ viruses which are sufficiently similar that one can infer comparable performance against SARS-CoV-2. The viruses most commonly used include Influenza A, Feline coronavirus (FCoV) and Human coronavirus (HCoV NL63). Our preference is generally to test against HCoV, since this is the most logical equivalent and the most meaningful from a consumer perception perspective. That being said, our test evidence suggests that it is more difficult to achieve good performance against HCoV than FCoV.

ASTM G21… Anti-mould activity. While it is feasible to use the ISO22196 or JIS Z 2801 methods for evaluating anti-fungal or anti-mould performance, it is more common to use the G21 test. This is a much longer test, typically carried out over a period of four weeks, with mould/fungal growth evaluated weekly.


Masterbatch Example of Manufacturing Capabilites

How effective are SteriTouch additives?

The performance of any antimicrobial additive is dependent on a number of factors… the material being ‘treated’, the target organisms, type & concentration of active substance, test method and environmental conditions all play a significant part. 

Provided an appropriate additive is used it is possible to provide excellent levels of performance compared with an untreated material, but it is essential that the efficacy is verified through diligent testing prior to making antimicrobial claims.

It is also important to note some considerations, often overlooked, which can significantly impact the properties of the treated material, both in terms of the antimicrobial performance and the potential compromise of vital material characteristics. These are discussed in more detail here.

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