How can I tell the difference between an antimicrobial plastic and a standard one?
In almost all cases, an antimicrobial plastic will be visually indiscernible from the same material without the antimicrobial. This can lead to confusion, particularly if a product is available in both antimicrobial and non-antimicrobial versions. In these instances, it can be useful to further modify the antimicrobial plastic with a means of visual detection.
While it isn’t possible to easily detect the antimicrobial additive itself, by blending the additive with a detectable material or taggant, it is possible to create a material that can be identified easily with relatively inexpensive equipment.
The most economical approach is to blend the antimicrobial with an optical brightener, which enables identification with a cheap UV light. This usually works best with light coloured plastics, but we have a particularly powerful brightener formulation that allows even black antimicrobial plastics to be easily differentiated from a non-antimicrobial.
While an optical brightener is a cheap and effective option, some customers prefer a laser detectable additive, such as “anti-stokes” or “up-conversion” phosphor taggants. These are inorganic phosphor compounds that convert lower energy light (e.g. infrared) into higher energy, visible light. The ‘detector’ would typically be a low cost laser pen with a wavelength of 950-980nm.
Both optical brighteners and anti-stokes phosphor additives provide a quick and easy visual confirmation, but it’s important to note that it is purely qualitative (i.e. yes/no). Quantitative detection is theoretically possible but in most practical applications our experience suggest that the accuracy is inadequate for a meaningful result.
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READ MOREHow long does an antimicrobial additive keep killing germs/bacteria?
The length of time for which antimicrobial materials remain active will depend on a number of considerations, including the type of antimicrobial additive, the material into which it is incorporated and environmental conditions.
Probably the most important consideration for the longevity of antimicrobial effect is the selection of the antimicrobial additive itself. Some are designed to remain active for many years, often exceeding the likely usable lifespan of the product in which they’re used, whereas others are engineered to deliver extremely high levels of performance over short periods, ideal for products that are highly susceptible to microbial contamination but have a very short functional life.
It is also important to consider the environment in which the antimicrobial plastic will be used. Some antimicrobial additives perform best in warm, humid conditions and their efficacy will be notably diminished in a cold, dry environment. Others can be significantly compromised by organic surface contamination.
Even if a particular antimicrobial additive has typically good longevity, this can be compromised by the material in which it is used. It is not unusual to see adverse interactions between an antimicrobial additive and polymers, coatings and resin systems. Sometime these interactions manifest as a change to the physical properties, such as colour or impact strength, but in many cases the interaction is a detrimental effect on antimicrobial performance. In some cases, this can be relatively insignificant, but in others it is possible for the antimicrobial properties to be entirely negated. It’s worth noting that even apparently similar materials can exhibit interactions at both ends of the scale. By way of example, incorporating the same antimicrobial additive, at the same concentration, into two different of ABS, even from the same manufacturer, can result in one material that performs extremely well and another with barely any discernible antimicrobial properties.
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READ MOREDoes Radical offer anti-viral plastics or coatings?
It is possible to modify a polymer or a coating so that the surface will deactivate viruses, including SARS-CoV-2. However, the mechanisms by which this occurs are debatable and there seems to be both a lack of understanding and a great deal of misinformation. Furthermore, in many countries the regulatory requirements for anti-viral claims make most applications cost prohibitive.
For these reasons, Radical does not typically offer anti-viral solutions, although we are happy to assist with research & development in this field.
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READ MORECan antimicrobial plastics be used in refrigerators?
Antimicrobial plastics have been used for many years in moulded fridge linings. The potential benefits would appear to make the additional cost worthwhile, but there are a number of important considerations.
A refrigerator would reasonably be expected to remain in service for perhaps ten years. Silver based antimicrobial additives, such as silver phosphate glass or silver zinc zeolite, would certainly provide adequate longevity, whereas organic antimicrobial alternatives are unlikely to remain active for that length of time. However, the temperature in a refrigerator is notably lower than that at which silver additives tend to be most effective. At the typical refrigeration temperature of 5°C bacteria are not particularly active and silver is most effective when bacteria are undergoing mitosis/cell division, so the efficacy of silver is significantly reduced.
It is worth noting that most silver efficacy data is drawn from standard ISO 22196 tests, which are conducted at 35°C, significantly higher than refrigeration temperature. Antimicrobial plastics which perform well at 35°C will not necessarily perform well at low temperatures…. the only way to be sure is to use a modified test protocol, testing at whatever temperature is relevant to the specific application.
In order to maximise low temperature performance, the choice of antimicrobial plastic becomes more important. Among materials typically used in fridge linings, ABS is probably the most common. Unfortunately, ABS can be quite problematic when used with silver antimicrobial additives, with some grades of ABS performing notably worse than others at a given concentration of antimicrobial. At normal usage temperatures the performance is generally improved by simply increasing the concentration of antimicrobial, but at refrigeration temperatures the loss of perfomance can be too great to overcome economically. The best option is generally to switch to a different grade of ABS.
With careful selection of both antimicrobial additive and polymer, it is certainly feasible to create an antimicrobial plastic that can perform well against bacteria at refrigeration temperatures. Of course, another consideration is the effect of antimicrobial additives on the physical properties of the plastic into which they are incorporated…. but that will be the subject of another post!
What is the difference between antimicrobial and antibacterial?
Antimicrobial and antibacterial are terms often used interchangeably, but they have distinct meanings…
Antimicrobial is a broader term which includes substances that can kill or inhibit the growth of any type of microorganism, including bacteria, fungi, viruses, and parasites.
Examples: Antibiotics, antifungal paints & coatings, antiviral drugs and antiparasitic medications.
Antibacterial is a narrower term, specifically refering to substances that kill or inhibit the growth of bacteria.
Examples: Antibacterial plastics, antibiotics, antibacterial soaps and disinfectants.
Antibacterial is essentially a subset of antimicrobial. All antibacterial substances are antimicrobial, but not all antimicrobial substances are antibacterial.
