Practical Implications of Treated Articles containing Antimicrobial Masterbatches

Practical Implications of Treated Articles containing Antimicrobial Masterbatches

During the 2024 Dublin Biocides Symposium in March, Joe Pearson, Evie Jenkins and Dr Stephen Rayner from Broadway Colours, a masterbatch manufacturing company, gave a presentation about the practical implications of treated articles containing antimicrobial masterbatches.

A masterbatch is a concentrated formula of colourants, performance enhancing additives, or a combination of the above, encapsulated within a carrier plastic resin. Some examples of products where an antimicrobial or antibacterial masterbatch may be used are whistles, medical furniture, toiletries and hygiene products, nursery furniture and water purification systems.

Zoe explained the mechanisms of the different technologies available on the market for antimicrobial additives for masterbatches. The most popular option has been the silver ion technology where the silver ions compromise the bacteria cell walls and disrupt the functions within the cell cycle leading to the death of the cell. Another way that antimicrobial additives work is by oxidative damage where oxygen in the air is combined with the antimicrobial additive and generates reactive oxygen species which disrupt microbial replication. The third and more novel technology includes biosurfactants which interfere with bacterial adhesion to polymer surfaces to maintain a sterile environment.

Zoe further discussed some of the customer considerations for choosing the most appropriate technology and antimicrobial additive such as the target microbe and the efficacy requirements. Most customers require a 3-log microbe reduction which equates to a 99.9% kill rate. The appearance of the final article such as the colour, opacity or effects is also taken into account at the colour matching stage. The polymer type of the masterbatch is carefully selected to ensure compatibility with the final article and the let-down rate, which is the percentage of the concentrated masterbatch added to the final polymer, is determined. The production method and use of the final article must be taken into account to select the right additive that does not decompose when processed or used. Finally, the regulatory requirements of the final article must also be considered to ensure compliance.

Evie explained the regulatory considerations for the production of an antimicrobial masterbatch. Broadway ensures compliance to the BPR regulation when selecting the right antimicrobial additive and focuses on PT2 & PT4 for disinfectants and PT7 & PT9 for preservatives. Evie explained that the other constituents of the masterbatch formulation must also comply with the regulatory requirements (i.e. CLP).

Evie emphasised the differences between polymer types and the effect this has on efficacy. For example, different polymers have dfferent water absorption characteristics and polymers with a greater tendency to absorb moisture will release more silver ions if it contains a silver ion based masterbatch. Therefore, the environmental conditions that the treated articles are used in also have a huge effect on efficacy. For this reason, Evie recommends testing the final product and not the masterbatch, for instance using ISO 22196 combined with accelerated weathering.

If you need support with efficacy testing or any other aspects of the registration of your biocidal products, please contact Kerona’s Biocide Team at info@kerona.ie

If you missed the symposium, you can download the slides here: Dublin Biocides Symposium 2024 – Speakers Presentations – Kerona Scientific Ltd.