Stinky Shoes and Other Aspects of Antimicrobial Textiles

Antimicrobial Textiles – What and Why?

Who hasn’t’ had a pair of sandals or shoes turn impossibly smelly, needing to be thrown away after only a few weeks of use?
It’s not your hygiene that causes this issue; most commonly this issue is due to inferior quality materials or manufacturing issues and the absence of an appropriate antimicrobial.

More often than not, the situation is entirely preventable.

Antimicrobial products are those that have an attribute that provides resistance to the growth of microorganisms such as bacteria, fungi, or algae. This performance is provided in the product by an additive to the main material and can be incorporated in many different ways.

Q: Why do we need antimicrobial anything?  (See the Rule of 3)

Antimicrobial textiles represent a category of textiles that provide the performance benefit by the use of an additive (called an auxiliary) which can be added in the makeup of the material such as in the dyeing process or at the end stage of production by padding (or spraying) creating a coating on the final material.

Common applications for antimicrobial textiles include:

  • Improved textile hygiene (hospitals or care facilities)
  • Provide longer term, durability against deterioration (outdoor or sporting goods apparel and products)
  • Applications where the potential for microorganism growth is nearly constant (shoes and sandals)
  • Commercial and public spaces  – long service life (outdoor, commercial, and public space upholstery or carpeting)
  • Short term protection for shipment of textiles or raw materials

The application of antimicrobials to a textile can be complicated.  Textile processing in general, is a highly managed process where factors of temperature, chemical additives, chemical incompatibilities, and processing conditions are continually managed.  What is important is that the process be well understood and that the additive selected for the antimicrobial benefit be appropriate for both the manufacturing process of the textile and the intended performance of the finished product.

For the purposes of this series of posts, we’ll discuss in general terms about the application and uses of antimicrobials  and then more specifically about different technologies that affect how and what can/should be done to create a product with antimicrobial performance.

Microorganisms and Textiles: 

There are two common types of textiles both of which can be further broken down into their fiber sub-types; Synthetic (fibers derived from man made material, such as polyester or nylon) and Cellulosic (fibers derived from natural materials, cotton, wool, or flax as examples); there are also crossover types such as rayon, which are cellulosic fibers processed into essentially synthetic material.   As textiles go, there is an endless level of fiber blending and combinations of the materials that can occur.

For our purposes, the importance of the fiber type lies in the way different fibers have different needs for the incorporation of antimicrobials.

It’s a misunderstanding that synthetic fibers don’t provide a ready food source for microorganisms.  Generally it is true that a product not intended for longer term or multiple uses does not grow abundant organisms.  But in the real world, we want our synthetic materials to last a long time, which is why we purchase them at extra expense.

As we know from the Rule of 3, all items accumulate dirt, oils, and grime, and once this begins it will lead to the growth of microorganisms and odor issues.

This is the case for nearly any material, from polyester, nylon, or polyethylene fiber and course cotton.  Once the Rule of 3 is satisfied by the addition of soil, and moisture, and air, organisms will begin to thrive on or in the material.   Once this occurs, they can further support other organisms that can physically degrade the material that they are growing on.

The most odor causing items are those that degrade as a results of the growth of microorganisms.  As part of their metabolism, microorganism’s produce acids, such as fatty acids, that can be volatile, and rancid (oxidized by air or other means).  The volatile acids are those that we can smell, like perfume but not as pleasant.  We’re all familiar with pink stain which is casued by many types of bacteria.

Antimicrobials and other additives come into play to support this issue.   Most textiles have numerous additives that provide the functions that we erroneously associate with the textile fibers, such as wicking, or soft plush feel, or antistatic..etc.  Each of these features is rarely solely a property of the textile at the end of its manufacturing, these features require other auxiliaries to provide these benefits.  Often these auxiliaries by virtue of their chemical properties will also provide some resistance to microorganisms.

The Consumer Conundrum

As a consumer, we want value for our money, but something as mundane as antimicrobial protection is essentially invisible.

The Challenge:  How can a manufacturer justify the added cost of incorporating an antimicrobial when the consumer can’t see the benefit, and if it works properly, will never realize the effectiveness of the product.
Buyer be-aware: In the textile industry, the battle against cost is continual; these auxiliaries cost a significant amount to add to the textile, and in the manufacturing process, both at addition and in removal via waste processing.  So minimizing these additives while maximizing the performance is a balance that at times is successful, and not.

Let experience be your guide:Quality Manufactures and Retailers know about antimicrobials, their benefits, and which suppliers can be relied on for appropriate application.  To Branded Manufactures and Retailers their brand is a testament to their quality.  If a product fails to meet your expectations, notify the supplier, they know who their manufacturers are (or they can find out) and at a minimum they can change their quality program to specify an antimicrobial performance specification that works.

Buyer be-active: As a consumer, if you have a poor experience with their product becoming smelly or otherwise inferior performance…tell them.   Retailers and manufacturers have the ability to specify the use of antimicrobials in their products, they either simply do not, or more commonly, have a supplier that does not know how.

As customers, take note the end product performance,

Were there odors that resisted washing
– How long until this occurred?

Were there yellowing issues?
Did it begin to smell up the hamper?
Did visible mold or mildew form on the item?

All could be indications that the product would benefit from the addition of or a better application of an antimicrobial auxiliary.

In our next post:

Common additives used in textiles; what and why.

About Us
Situ Biosciences LLC
We are an independent laboratory performing microbial product testing including antimicrobial performance, biodegradability and product development for the microbial products industry.