At BioCote® our partners and clients have come to rely on the high quality and efficacy of our additives, delivering ultimate antimicrobial product protection. To ensure our additives meet those high expectations at all times, we apply stringent quality control parameters and test protocols prior to deploying our additives. In her blog, BioCote® chemist, Ruvimbo Chitera, explains the quality control parameters for our silver-based powder additives.
The impact of particle size on treated materials
Whilst the average human eye may not be able to tell the difference between different particle sizes of powder addtitives, the impact the particle size can have on the end product is large (no pun intended).
The below graphic highlights some of the key features that are affected by the particle size and why it is important.
Luckily, a laser scattering instrument can tell the difference in particle size. The theory behind a laser scattering instrument is that a particle will scatter light at an angle determined by that particle’s size. Larger particles will scatter at small angles and smaller particles scatter at wide angles. A collection of particles will produce a pattern of scattered light defined by intensity and angle that can be transformed into a particle size distribution result. A smaller particle has a larger surface area to volume ratio and will form aggregates which require more energy to break them up. This affects the rate of dispersion compared to a large particle size. This is the reason why BioCote® offer powders with different particle sizes to suit the needs of a client’s end-product.
The impact of moisture on antimicrobial efficacy
Even if you were able to spot the different particle sizes of powder, you probably would struggle to safely identify the exact moisture content of different powders. Luckily, technology comes to our rescue again, this time in form of a Karl-Fischer moisture titrator.
In the Karl Fischer reaction, water from the sample reacts with iodine and sulphur dioxide in the presence of a base and alcohol. As soon as the detector senses the decline of iodine levels, it starts electrolysis to generate iodine in the analyte to restore its equilibrium. The amount of water in the sample is then calculated based on the current consumed for this electrolysis.
The moisture content in our antimicrobial additives is a crucial measure, as moisture can alter the structure of the glass carriers in our silver ion additives which would minimise the antimicrobial activity of our additives. A raised moisture content would also become visible to the human eye, as the altered glass carrier structure would release silver ions which are quickly get reduced to metallic silver leaving a brownish appearance. At BioCote® we ensure that no powder additives leave our warehouse with more than 2% of moisture content in each batch, ensuring the high quality and efficacy of our additives.
Appearance as a sign of efficacy
At BioCote®, we take the visual appearance of our powder additives seriously and brown is not our colour. How our powder looks is not a vanity issue though, but it reflects on the efficacy of the antimicrobial properties in our powders.
A visual examination is undertaken on all our powder-based additives during manufacture. Exposure to conditions such as high wavelength of light and the use of reducing agents can cause dissociation of silver ions, leaving them free to be reduced to metallic silvers characterised by a brownish appearance. The colour of our powder additives should be white, so during manufacture we look out for any reactions that may have occurred and have led to discolorations to ensure only high performing additives make their way to our clients.
The right silver concentration to achieve antimicrobial efficacy
As part of our quality control process, we have so far chosen the right particle size, checked for moisture content and are happy with the appearance of our powder additive. However, without the right concentration of our active substance we really have nothing to show for.
The concentration of our additives affects the dosage rate and antimicrobial efficacy. We employ Atomic Absorption Spectroscopy (AAS) that uses light absorption to determine the concentration of a chemical element, in our case silver. The instrument provides quantitative results, which then gives us an indication of the dosage rate we need in the final product to pass antimicrobial efficacy.
At BioCote® we have a minimum and a target concentration that our additives need to reach. If the concentration of the additive batch does not reach the minimum level, the powder is classified as a fail and is discarded off. Only additives achieving our target concentration will be sent to customers to integrate into their products, delivering optimum antimicrobial protection.
How BioCote® can support you
BioCote® premium additives can be integrated into a wide range of materials, including polymers, silicones, powder coatings, liquid paints, ceramics and textiles. If you would like to learn more about our antimicrobial technology or if you are looking to make your products antimicrobial, please contact a member of the BioCote® team today on +44 (0) 2477 712 489 or email us at [email protected]. Alternatively, you can contact us via the form below.