The Best Antimicrobial Additive

or “Which antimicrobial is best?”

…unfortunately it’s not so simple.

Product manufacturers have a challenging task when it comes to selecting antimicrobials for their products. Very few manufacturers have access to either in-house microbiology or formulation experts, or contract laboratories that have both microbial facilities and sufficient expertise in their product requirements.

Details matter.

For the purposes of creating a framework for considering some common questions, we’ll divide the types of performance requirements into three types or subsets of performance.

• General Antimicrobial – The microorganisms targeted (commonly bacteria, fungi or algae; or a mix of different organism types.
• Application Specific – A level of general performance, such as outdoor exposure, durability, UV durability; 10 year durability etc. These are centered around the intended use of the product and specific product claims or the product label.
• Test Method Performance – A specific test requirement such as ASTM, ISO, AATCC, or Military Standard. Examples include ASTM G21 and the Military Standard 810 specification; both methods test for performance against fungi, but are conducted in a very different manner and ultimately for very different purposes.

Details matter.

One of the challenges in the antimicrobial industry is that there are few iron clad criteria that hold true for any given circumstance. More often, there are guidelines the provide an appropriate path to obtaining a level of product performance that will satisfy a specific requirement.

For both product development and quality control management we’ve assembled this guidance that will help in understanding the best approach to dealing with additives, products and microorganisms.

Getting started …

In general there are two broad categories of products which use antimicrobial additives – liquids and solids.

Liquids are typically products needing preservation (water based solutions), but some material such as un-cured coating base (liquid then solid) also use antimicrobial additives as part of their finished product performance.

Solids can be nearly any material type, examples of the range of product types include: plastics, coatings, concrete, wood, paper, foam and mixtures of materials (resin and stone) etc.

What is important is not the product types, but the chemical compatibility between the product components and the additives used for the specific performance.

For the antimicrobial additive, its form is significant but should not be viewed as a limitation, whether a liquid or solid; depending on the product needs, nearly any additive can be universally incorporated with the appropriate blending formulations and incorporation techniques, what’s more important is the technical and chemical details of a particular product and its use.

For the finished products, such as a solid plastic how the antimicrobial is added, its chemical limitations, the identity of its true processing durability specifications; make the critical difference as to where a given supplier can provide a cost effective, and functional additive for your product or application.

Some examples of important antimicrobial additive characteristics:

• hydrophobicity (water repellent)
• hydroscopic (water attracting)
• solubility
• pH stability
• manufacturing conditions
  • mixing energy
  • temperature zones
  • presence of catalyst
• Other additives, oxidative scavengers

In our global work with manufacturers incorporating antimicrobial additives there are few guidelines that are universally true.

But in an effort to simplify the formulation landscape here some of the key questions that refine the list of additives that can then be further evaluated for fitness of purpose:

• What are the target environments or target organisms for the manufacturers’ product?

Bacteria, fungi, and algae all have different sensitivities for different additives.

•  What is the durability specification for the finished product?

…including specific environmental variables such as UV exposure, water exposure, mechanical and other components that will impact the usable life of the manufactured product.

• What is the cost target for the additive?

It may be a surprise, but cost, additive selection and durability are critically related and the targets should be identified as early as possible.

Once these characteristics have been examined, then begin determining which additives best fit the production conditions and other variables that could also impact the appropriateness of a given additive over other additives.   In all likelihood if there are limitations beyond the initial three questions the product or manufacturing conditions can be adjusted to overcome issues that may be present.

Once the appropriate antimicrobial additive has been incorporated into the product, antimicrobial testing for durability, compatibility, antimicrobial performance, and cosmetic issues can then be done to assure that the product will meet the quality expected and performance expected.  This level of testing applies to all microbial applications such as antimicrobials for bacteria, fungi, and algae.  Each will have a unique set of nuances that can propel a successful product or hinder one with problems and issues.