In a climate of pandemics, acquired immune diseases, and common viruses, the demand for products claiming to have anti-microbial properties has risen substantially. The textile industry has not been immune to the phenomena.
Whether it is for consumer, commercial, or institutional applications, textile manufacturers, converters, and chemical vendors have risen to provide an array of anti-microbial product offerings with an assortment of product claims. The challenge is to discern fact from hype. This article documents the findings of a study that explored the efficacy of three different anti-microbial coatings and additives as tested.
ANTI-MICROBIAL TREATMENTS DO NOT ALL PERFORM IN THE SAME MANNER
The vast majority of anti-microbials work by leaching or moving from the surface on which they are applied. Leaching anti-microbials will poison a microorganism. Such chemicals have been used for decades in agricultural applications with mixed results. In addition to affecting durability and useful life, leaching technologies have the potential to cause a variety of other problems when used in textiles or garments, including skin irritation and the potential to affect normal skin bacteria. There are several types of anti-microbials that apply to this discussion including both topical and permanent finishes.
Topical anti-microbial finishes usually include quaternary ammonium cations, also known as quaternary ammonium salts, quaternary ammonium compounds, or “Quats.” The majority of applications for quaternary ammonium compounds are related to their very strong affinity for surfaces, which can make them powerful surfactants. The quaternary ammonium compounds adsorb on almost any surface and can be introduced into a laundry rinse cycle for most fabrics, as a temporary anti-microbial agent. Chlorine and oxygenated bleach charged anti-microbial finishes are also found in the realm of topical finishes. There are essentially two schools of thought for this part of the discussion. The first includes textile manufacturers and converters that are now presenting fabrics that claim to retain high levels of chlorine to kill microbes. The second school utilizes oxygenated bleach including hydrogen peroxide and peracidic acid to sanitize products, whereby chemistry is added to a laundry wash step to sanitize a laundered product.
Permanent anti-microbial finishes include Bound Unconventional Anti-microbial Technology, or an organofunctional silane, that has a mode of action that relies on the technology remaining affixed to the substrate, killing microorganisms as they contact the surface to which it is applied. Excluding substances like silver, there are essentially two technologies that have evolved for permanent finishes. The more exploited technology consists of silicon, organic alcohol, hydrocarbons (methanol), and nitrogen. This technology must be added at the fabric manufacturing stage. The second permanent finish consists of propyldimethyloctadecyl ammonium, which is considered to be food safe. These products can be added to a rinse like a “Quat” agent for semi-permanent results, or at the fabric manufacturing stage for a permanent finish. Bound Unconventional Anti-microbial Technology, or an organofunctional silane, has a mode of action that relies on the technology remaining affixed to the substrate, killing microorganisms as they contact the surface to which it is applied.
THE STUDY
In order to evaluate the efficacy of two permanent and one topical anti-microbial technology on industrially laundered garments, AmeriPride and Canadian Linen and Uniform Services undertook three studies at their Toronto, Ontario, branch whereby a set of treated and non-treated garments were intentionally soiled with Staphylococcus aureus and then washed in a non-bleach wash formula to assess the ability of the fabric coating or treatment to reduce pathogen based bioburden as measured in colony for ming units (CFUs). The trial subjected the garments to 25 soil and wash replicates to assess the garments’ ability to reduce bioburden. Each study was conducted over an approximate four week period, with sampling done for each gar ment after drying.
Each trial tested a total of 20 garments made from 100% polyester. A control sample of ten garments had no pre-treatment applied to them, whereas ten gar ments were received with either a permanent finish or subjected to an anti-microbial treatment in the laundry process. The garments were then washed and dried in separate lots to eliminate cross contamination. Garments were washed in a 125 pound industrial-type washer, and dried in a 125 pound industrial-type gas dryer using a bleach free standard commercial wash formula. The wash formula included an alkali, non-ionic detergent and sour to reduce pH during the final wash step.
Prior to each wash cycle, each garment from each “Set” was contaminated with Staphylococcus aureus at the collar area. After the wash cycle, each garment from each “Set” was sampled using a Tryptic Soy Agar (TSA) with Lecithin and Polysorbate 80 (Tween 80), Rodac™ plate. The front and back surfaces of each collar were tested by placing the Rodac™ plate firmly on the fabric surface. The plates were then incubated for aerobic bacteria for three days at 32°C +/-2°C and then an additional two days for molds and yeasts at room temperature. Incubated Rodac™ plates were then sent to a third party laboratory for testing and evaluation. Target values were set at less than 47 CFU per garment. Any garments with a value higher than 47 CFU would be deemed unacceptable for use.
The first trial utilized a permanent finish consisting of Bound Unconventional Antimicrobial Technology which included propyldimethyloctadecyl ammonium.
The second trial utilized organofunctional silanes that included silicon, organic alcohol, hydrocarbons (methanol), and nitrogen.
The third trial utilized a topical treatment of oxygenated bleach. During this trial, the control Set of garments was not subjected to the topical treatment.
At the end of each trial, after the 25 wash cycles per garment, the two Sets of garments were then contaminated once again with Staphylococcus aureus for 144 hours. The two Sets were then tested for bioburden and then tested again after a wash cycle as described.
FINDINGS
For the first trial which utilized a permanent finish of propyldimethyloctadecyl ammonium the data yielded little difference in CFU counts from the treated garments to un-treated control group, with the exception of one sample within the control group that had <200 CFU as tested. Otherwise, the data had little variance and performed in a similar fashion.
However, when the garments were subjected to the 144 hour soiling period, the observations differed substantially, though only after being subjected to the final wash cycle. The treated and non-treated garments yielded similar CFU counts at the soil stage, but the treated garments had significantly lower CFU counts after the final wash cycle. Of the non-treated garments, one garment failed to have less than 47 CFU. For the treated garments, all garments had very low CFU counts, and showed significant log reductions in bioburden.
For the second trial which utilized organofunctional silanes, the data yielded little difference in CFU counts from the treated garments to un-treated control group, with the exception of five samples within the treated group and three samples in control group that had <2800 CFU after the fifth wash cycle as tested, and four samples within the treated group and three samples in control group that had <2800 CFU after the seventh wash cycle. The wash trials produced eight more failures for the treated garments than for the controlled group, which was unexpected.
When the garments were subjected to the 144 hour soiling period, the observations did not differ substantially. The treated and non-treated garments yielded similar CFU counts at the soil stage and after the final wash cycle, which was also unexpected.
For the third trial which utilized oxygenated bleach products, the data gathered yielded little difference in CFU counts from the treated garments to un-treated control group. The treated garments however, showed a very consistent and low, single digit CFU reading, which was very encouraging.
When the garments were subjected to the 144 hour soiling period, the observations did not differ substantially after being subjected to the final wash cycle. The treated and non-treated garments yielded similar CFU counts at the soil stage, and the treated garments had consistently low CFU counts after the final wash cycle. The nontreated garments also exhibited low CFU counts, though less consistently than the treated group. For the treated garments, all garments had very low CFU counts, and showed significant log reductions in bioburden.
SUMMARY
The three trials generated some interesting and surprising results. Most notably the poor results demonstrated by the garments treated with organofunctional silanes. This treatment can be found on a number of textiles that include continuous polyester filament cleanroom products and a wide array of consumer sportswear products. The relatively strong performance of the control groups for each of the three trials was also unexpected. The theories that support most anti-microbial treatments are based upon disruption of bacteria or biofilms. The demonstration of an untreated fabric performing even reasonably well, with low or moderate CFU levels, challenged some of these assumptions and may lend credence to European assertions regarding minimum temperature, pH, and surfactant levels for the reprocessing of these textiles.
The trial utilizing propyldimethyloctadecyl ammonium as a permanent treatment showed promising, though inconsistent results, with the exception of the 144 hour contamination challenge, where it appeared to assist the wash efficacy and removal of the Staphylococcus aureus contamination. Similarly, the treatment utilizing oxygenated bleach appeared to assist the wash efficacy during the 144 hour contamination challenge and yielded consistent CFU counts for the treated garments.
The most intriguing result from all three trials was the performance of the control sets of garments. With a few exceptions during the second trial, they performed well, with counts well within an acceptable range, lending credence to the value of a stringent wash and handling process.
It is important to note that it is not the intent of this article to recommend or support any of the presented technologies.
Robert Nightingale is Director of Quality, Research, and Development for Ameripride Services Inc., Canadian Linen and Uniform Services, and their CleanStyle Cleanroom Division. He has over 20 years of experience in human source contamination and cleanroom apparel processing, as founder and President of Cleanroom Garments ™, with multiple cleanrooms supporting a vast array of cleanroom applications from aseptic fill operations, aerospace, and MEMS fabrication, to automotive paint spray operations. Robert is also a co-owner of several international patents for cleanroom soil removal processes.
Whether it is for consumer, commercial, or institutional applications, textile manufacturers, converters, and chemical vendors have risen to provide an array of anti-microbial product offerings with an assortment of product claims. The challenge is to discern fact from hype. This article documents the findings of a study that explored the efficacy of three different anti-microbial coatings and additives as tested.
ANTI-MICROBIAL TREATMENTS DO NOT ALL PERFORM IN THE SAME MANNER
The vast majority of anti-microbials work by leaching or moving from the surface on which they are applied. Leaching anti-microbials will poison a microorganism. Such chemicals have been used for decades in agricultural applications with mixed results. In addition to affecting durability and useful life, leaching technologies have the potential to cause a variety of other problems when used in textiles or garments, including skin irritation and the potential to affect normal skin bacteria. There are several types of anti-microbials that apply to this discussion including both topical and permanent finishes.
Topical anti-microbial finishes usually include quaternary ammonium cations, also known as quaternary ammonium salts, quaternary ammonium compounds, or “Quats.” The majority of applications for quaternary ammonium compounds are related to their very strong affinity for surfaces, which can make them powerful surfactants. The quaternary ammonium compounds adsorb on almost any surface and can be introduced into a laundry rinse cycle for most fabrics, as a temporary anti-microbial agent. Chlorine and oxygenated bleach charged anti-microbial finishes are also found in the realm of topical finishes. There are essentially two schools of thought for this part of the discussion. The first includes textile manufacturers and converters that are now presenting fabrics that claim to retain high levels of chlorine to kill microbes. The second school utilizes oxygenated bleach including hydrogen peroxide and peracidic acid to sanitize products, whereby chemistry is added to a laundry wash step to sanitize a laundered product.
Permanent anti-microbial finishes include Bound Unconventional Anti-microbial Technology, or an organofunctional silane, that has a mode of action that relies on the technology remaining affixed to the substrate, killing microorganisms as they contact the surface to which it is applied. Excluding substances like silver, there are essentially two technologies that have evolved for permanent finishes. The more exploited technology consists of silicon, organic alcohol, hydrocarbons (methanol), and nitrogen. This technology must be added at the fabric manufacturing stage. The second permanent finish consists of propyldimethyloctadecyl ammonium, which is considered to be food safe. These products can be added to a rinse like a “Quat” agent for semi-permanent results, or at the fabric manufacturing stage for a permanent finish. Bound Unconventional Anti-microbial Technology, or an organofunctional silane, has a mode of action that relies on the technology remaining affixed to the substrate, killing microorganisms as they contact the surface to which it is applied.
THE STUDY
In order to evaluate the efficacy of two permanent and one topical anti-microbial technology on industrially laundered garments, AmeriPride and Canadian Linen and Uniform Services undertook three studies at their Toronto, Ontario, branch whereby a set of treated and non-treated garments were intentionally soiled with Staphylococcus aureus and then washed in a non-bleach wash formula to assess the ability of the fabric coating or treatment to reduce pathogen based bioburden as measured in colony for ming units (CFUs). The trial subjected the garments to 25 soil and wash replicates to assess the garments’ ability to reduce bioburden. Each study was conducted over an approximate four week period, with sampling done for each gar ment after drying.
Each trial tested a total of 20 garments made from 100% polyester. A control sample of ten garments had no pre-treatment applied to them, whereas ten gar ments were received with either a permanent finish or subjected to an anti-microbial treatment in the laundry process. The garments were then washed and dried in separate lots to eliminate cross contamination. Garments were washed in a 125 pound industrial-type washer, and dried in a 125 pound industrial-type gas dryer using a bleach free standard commercial wash formula. The wash formula included an alkali, non-ionic detergent and sour to reduce pH during the final wash step.
Prior to each wash cycle, each garment from each “Set” was contaminated with Staphylococcus aureus at the collar area. After the wash cycle, each garment from each “Set” was sampled using a Tryptic Soy Agar (TSA) with Lecithin and Polysorbate 80 (Tween 80), Rodac™ plate. The front and back surfaces of each collar were tested by placing the Rodac™ plate firmly on the fabric surface. The plates were then incubated for aerobic bacteria for three days at 32°C +/-2°C and then an additional two days for molds and yeasts at room temperature. Incubated Rodac™ plates were then sent to a third party laboratory for testing and evaluation. Target values were set at less than 47 CFU per garment. Any garments with a value higher than 47 CFU would be deemed unacceptable for use.
The first trial utilized a permanent finish consisting of Bound Unconventional Antimicrobial Technology which included propyldimethyloctadecyl ammonium.
The second trial utilized organofunctional silanes that included silicon, organic alcohol, hydrocarbons (methanol), and nitrogen.
The third trial utilized a topical treatment of oxygenated bleach. During this trial, the control Set of garments was not subjected to the topical treatment.
At the end of each trial, after the 25 wash cycles per garment, the two Sets of garments were then contaminated once again with Staphylococcus aureus for 144 hours. The two Sets were then tested for bioburden and then tested again after a wash cycle as described.
FINDINGS
For the first trial which utilized a permanent finish of propyldimethyloctadecyl ammonium the data yielded little difference in CFU counts from the treated garments to un-treated control group, with the exception of one sample within the control group that had <200 CFU as tested. Otherwise, the data had little variance and performed in a similar fashion.
However, when the garments were subjected to the 144 hour soiling period, the observations differed substantially, though only after being subjected to the final wash cycle. The treated and non-treated garments yielded similar CFU counts at the soil stage, but the treated garments had significantly lower CFU counts after the final wash cycle. Of the non-treated garments, one garment failed to have less than 47 CFU. For the treated garments, all garments had very low CFU counts, and showed significant log reductions in bioburden.
For the second trial which utilized organofunctional silanes, the data yielded little difference in CFU counts from the treated garments to un-treated control group, with the exception of five samples within the treated group and three samples in control group that had <2800 CFU after the fifth wash cycle as tested, and four samples within the treated group and three samples in control group that had <2800 CFU after the seventh wash cycle. The wash trials produced eight more failures for the treated garments than for the controlled group, which was unexpected.
When the garments were subjected to the 144 hour soiling period, the observations did not differ substantially. The treated and non-treated garments yielded similar CFU counts at the soil stage and after the final wash cycle, which was also unexpected.
For the third trial which utilized oxygenated bleach products, the data gathered yielded little difference in CFU counts from the treated garments to un-treated control group. The treated garments however, showed a very consistent and low, single digit CFU reading, which was very encouraging.
When the garments were subjected to the 144 hour soiling period, the observations did not differ substantially after being subjected to the final wash cycle. The treated and non-treated garments yielded similar CFU counts at the soil stage, and the treated garments had consistently low CFU counts after the final wash cycle. The nontreated garments also exhibited low CFU counts, though less consistently than the treated group. For the treated garments, all garments had very low CFU counts, and showed significant log reductions in bioburden.
SUMMARY
The three trials generated some interesting and surprising results. Most notably the poor results demonstrated by the garments treated with organofunctional silanes. This treatment can be found on a number of textiles that include continuous polyester filament cleanroom products and a wide array of consumer sportswear products. The relatively strong performance of the control groups for each of the three trials was also unexpected. The theories that support most anti-microbial treatments are based upon disruption of bacteria or biofilms. The demonstration of an untreated fabric performing even reasonably well, with low or moderate CFU levels, challenged some of these assumptions and may lend credence to European assertions regarding minimum temperature, pH, and surfactant levels for the reprocessing of these textiles.
The trial utilizing propyldimethyloctadecyl ammonium as a permanent treatment showed promising, though inconsistent results, with the exception of the 144 hour contamination challenge, where it appeared to assist the wash efficacy and removal of the Staphylococcus aureus contamination. Similarly, the treatment utilizing oxygenated bleach appeared to assist the wash efficacy during the 144 hour contamination challenge and yielded consistent CFU counts for the treated garments.
The most intriguing result from all three trials was the performance of the control sets of garments. With a few exceptions during the second trial, they performed well, with counts well within an acceptable range, lending credence to the value of a stringent wash and handling process.
It is important to note that it is not the intent of this article to recommend or support any of the presented technologies.
Robert Nightingale is Director of Quality, Research, and Development for Ameripride Services Inc., Canadian Linen and Uniform Services, and their CleanStyle Cleanroom Division. He has over 20 years of experience in human source contamination and cleanroom apparel processing, as founder and President of Cleanroom Garments ™, with multiple cleanrooms supporting a vast array of cleanroom applications from aseptic fill operations, aerospace, and MEMS fabrication, to automotive paint spray operations. Robert is also a co-owner of several international patents for cleanroom soil removal processes.
