Antimicrobial masterbatch developed and manufactured in the UK
Radical Materials develops and manufactures CLENZED™ antimicrobial masterbatches and compounds for plastics, silicone and rubber. With more than 20 years’ experience in antimicrobial polymer development, we produce polymer-specific and custom antimicrobial formulations for injection moulding, extrusion and other manufacturing processes.
If you are looking for an antimicrobial masterbatch for a specific polymer or application, see our CLENZED™ antimicrobial masterbatch, additives and compounds.
An antimicrobial masterbatch is a concentrated mixture of antimicrobial additives compounded into a suitable polymer carrier and formed into pellets. It is incorporated into the bulk polymer during processes such as extrusion or injection moulding to provide antimicrobial functionality within the finished material.
What is an antimicrobial masterbatch?
An antimicrobial masterbatch is a concentrated formulation of antimicrobial active substances dispersed within a polymer carrier. It is added to a base polymer during manufacturing so that antimicrobial functionality becomes incorporated throughout the finished plastic component.
Masterbatches provide a practical way of introducing antimicrobial technology during conventional processes such as injection moulding, extrusion, blow moulding and profile extrusion without requiring the manufacturer to handle low concentrations of active ingredients directly.
The concept is simple, but an effective antimicrobial masterbatch must be formulated around the polymer, processing conditions, target microorganisms and finished application. A masterbatch that performs well in polypropylene, for example, should not automatically be assumed to be suitable for PVC, TPU, nylon or an engineering polymer.
How does an antimicrobial masterbatch work?
During processing, the antimicrobial masterbatch is blended with the base polymer at a predetermined addition rate. As the material melts and mixes, the antimicrobial system becomes dispersed throughout the polymer.
Once the component has been moulded or extruded, active antimicrobial species present at or available to the surface can inhibit the growth of susceptible microorganisms.
Different antimicrobial technologies work in different ways. Inorganic silver-ion systems are widely used because of their thermal stability and suitability for many polymer-processing applications. Other technologies may be selected where the objective is to control mould, fungi or specific microorganisms.
The important point is that antimicrobial performance comes from the complete finished formulation, not simply from the presence of an antimicrobial ingredient.
Why use a masterbatch rather than adding the antimicrobial directly?
A masterbatch allows a relatively small quantity of active material to be incorporated consistently into a much larger quantity of polymer.
A correctly formulated antimicrobial masterbatch can provide:
- more uniform dispersion of the antimicrobial technology;
- easier handling during production;
- accurate dosing during moulding or extrusion;
- compatibility with conventional polymer-processing equipment;
- improved consistency between production batches; and
- a practical route for introducing antimicrobial functionality without unnecessarily changing the customer’s base polymer.
The carrier system is particularly important. It must be compatible with the host polymer and capable of dispersing the antimicrobial technology effectively under the intended processing conditions.
Why does the carrier polymer matter?
An antimicrobial masterbatch is not simply antimicrobial powder mixed into any convenient plastic. The carrier can influence dispersion, processing behaviour, surface appearance, mechanical properties and potentially antimicrobial efficacy.
Where possible, the carrier should be selected to suit the polymer being treated. A polypropylene-based system may be appropriate for PP, while a different carrier may be preferable for TPU, PVC, nylon, POM or Polyketone (PK/POK).
Using an unsuitable carrier can introduce problems such as:
- poor dispersion;
- haze or surface defects;
- changes in impact strength or flexibility;
- phase separation;
- colour variation;
- processing instability; or
- inconsistent antimicrobial performance.
This is why a universal antimicrobial masterbatch is rarely the optimum solution for every polymer.
Which polymers can be made antimicrobial?
Antimicrobial masterbatches and compounds can be developed for a wide range of thermoplastics and elastomers, including polypropylene (PP), polyethylene (PE), TPU, PVC, nylon/PA, POM/acetal, ABS, polycarbonate, PC/ABS, PBT, PMMA, HIPS, Polyketone (PK/POK), polysulfone (PSU), silicone and rubber.
Each polymer presents different formulation challenges.
High-temperature engineering polymers require antimicrobial technologies and carriers capable of tolerating demanding processing conditions. Transparent polymers may require particular attention to haze and colour, while flexible polymers may be sensitive to changes in elongation, hardness or tear strength.
The antimicrobial formulation should therefore be developed alongside the material requirements of the finished component.
What addition rate is used?
There is no universal addition rate for an antimicrobial masterbatch.
The optimum concentration depends on factors including:
- antimicrobial technology;
- active concentration within the masterbatch;
- polymer type and grade;
- processing method;
- target microorganisms;
- required level of efficacy;
- component geometry;
- operating environment;
- colour and appearance requirements; and
- other additives already present in the formulation.
The objective should be to use the lowest practical concentration that delivers the required antimicrobial performance without unnecessarily affecting the properties of the polymer.
Higher loading does not automatically mean better performance.
Antibacterial, anti-mould and antimicrobial are not the same thing
The term antimicrobial covers a broad range of microorganisms, but individual technologies may target different groups.
An antibacterial masterbatch may perform very well against organisms such as Escherichia coli or Staphylococcus aureus while offering little protection against mould or fungi.
Where mould resistance is required, a specific antifungal or anti-mould technology may be needed. Likewise, antibacterial performance should not be assumed to indicate antiviral efficacy.
The technology should therefore be selected according to the actual microorganisms relevant to the application, rather than relying on a generic antimicrobial label.
How is antimicrobial masterbatch tested?
Antimicrobial efficacy should be evaluated in the finished polymer, because formulation, dispersion and surface characteristics can all influence performance.
Common test methods include:
ISO 22196
Used to measure antibacterial activity on treated non-porous surfaces.
ASTM G21
Used to assess resistance of polymeric materials to fungal growth.
ISO 21702
Used to evaluate antiviral activity on plastics and other non-porous surfaces.
At Radical Materials, antimicrobial efficacy testing is carried out by independent external laboratories. Formulation, compounding, processing trials, specimen moulding and relevant material testing are carried out in-house.
This approach combines rapid material development with independent verification of antimicrobial performance.
Why does application-specific antimicrobial testing matter?
Standard laboratory tests are valuable, but they do not necessarily represent the conditions experienced by the finished product.
Antimicrobial performance can be influenced by:
- temperature;
- humidity;
- contact time;
- polymer type;
- surface finish;
- ageing;
- cleaning chemicals;
- contamination level; and
- the microorganism being tested.
A material intended for a refrigerated food-processing environment, for example, should not be assumed to behave identically at 5°C and at conventional laboratory test temperatures.
Radical Materials has independently tested antimicrobial polymer formulations at refrigeration temperature against organisms including E. coli, Listeria monocytogenes and Salmonella, allowing performance to be assessed under conditions more representative of chilled food-processing applications.
Will antimicrobial masterbatch affect mechanical properties?
Any additive has the potential to influence polymer properties.
Depending on the technology and loading, antimicrobial modification may affect:
- impact strength;
- elongation;
- stiffness;
- viscosity or melt flow;
- colour;
- transparency;
- surface finish; or
- processing behaviour.
These effects are not necessarily significant, but they should be considered during development.
Where required, Radical Materials can compound trial formulations and mould test specimens including plaques, tensile dogbones and impact bars so that antimicrobial performance can be evaluated alongside relevant material properties. Plaques can also be produced for antimicrobial or UV exposure testing.
Can antimicrobial masterbatch be used in food-contact applications?
Yes, but food-contact suitability must be assessed for the complete formulation and intended use, not simply the antimicrobial active.
Relevant considerations may include:
- regulatory status of the active substances;
- carrier polymer;
- masterbatch addition rate;
- migration requirements;
- food type;
- contact time;
- operating temperature; and
- the jurisdiction in which the finished article will be marketed.
A statement that an antimicrobial ingredient is suitable for food-contact use does not, by itself, establish compliance of the final plastic article.
Can antimicrobial technology be combined with other properties?
Yes. Antimicrobial functionality can be incorporated alongside other material requirements.
Examples include:
- metal detectability;
- X-ray detectability;
- UV stabilisation;
- colour;
- antistatic properties;
- electrical conductivity;
- thermal conductivity; and
- odour or VOC control.
Multifunctional materials need to be formulated as a complete system because individual additives can interact with one another.
This is particularly important where antimicrobial efficacy must be retained alongside demanding mechanical, processing, aesthetic or regulatory requirements.
Antimicrobial masterbatch vs a fully compounded polymer
An antimicrobial masterbatch is a concentrated additive system intended to be blended with the customer’s base polymer during processing.
A fully compounded antimicrobial polymer is supplied ready to process, with the antimicrobial technology and any other required additives already incorporated into the material.
Masterbatch is often the most practical option where the customer wants to retain an existing polymer grade and control dosing during manufacture.
A fully compounded material may be preferable where tighter control is required over the complete formulation or where several functional properties need to be combined.
How Radical Materials develops antimicrobial masterbatches
Every CLENZED™ project begins with the requirements of the finished application rather than with a predetermined additive.
We consider the polymer, manufacturing process, target microorganisms, operating environment, regulatory requirements and mechanical or aesthetic constraints before selecting the most appropriate antimicrobial technology and carrier system.
Development can then progress through small-scale compounding, processing trials, antimicrobial testing, material testing and formulation optimisation before scale-up into commercial manufacture.
While antimicrobial efficacy testing is always conducted by independent laboratories, formulation, compounding, processing trials, specimen moulding and material testing are carried out in-house, allowing development times to be significantly reduced.
In many cases, we can formulate, compound and supply a new antimicrobial masterbatch for initial customer trials within 1–2 working days.
CLENZED™ technology can be supplied as a concentrated antimicrobial masterbatch, custom additive system or fully compounded antimicrobial polymer, depending on the application.
Choosing an antimicrobial masterbatch
The most appropriate antimicrobial masterbatch is not necessarily the one containing the highest concentration of active ingredient.
A technically sound selection should consider the polymer, manufacturing process, target microorganisms, application environment, regulatory requirements, required material properties and independent efficacy testing together.
Treating these factors as part of a complete material-development process usually produces a more reliable result than selecting an antimicrobial additive in isolation and attempting to make the rest of the formulation accommodate it.
For manufacturers developing antimicrobial plastic components, the key question is therefore not simply “Which antimicrobial should we add?”
It is “Which antimicrobial formulation will work effectively in this polymer, manufacturing process and finished application?”
