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.
