A new, durable antimicrobial finish for textiles

Table of Contents

Abstract
Introduction
In Vitro Microbiological Studies
In Vivo Organoleptic Evaluation
Application of Antimicrobial to Other Textiles
Conclusion
References
Tables I - II - III - IV V

Abstract:

The AEM 5700 Antimicrobial Agent (formerly known as the Dow Corning 5700 Antimicrobial Agent) imparts a durable, antimicrobial finish to textiles. The finish protects the fabric against bacteria and fungi which cause deterioration. It also inhibits the growth of odor-causing bacteria in In Vitro tests. In Vivo organoleptic tests confirm the practicality of this concept under actual use conditions in socks.

Introduction:

The need to preserve fabrics against rotting and mildew stain, particularly in industrial usage, has long been recognized. However, the use of biostats to inhibit odor development resulting from biological growth on textiles exposed to perspiration had not been considered a real need until relatively recently. The greater use of synthetic fibers and blends in such items as shirts, hosiery, blouses, and underwear has accelerated the need for bacteriostatic finishes on clothing. The moisture-transport characteristics of such blends tend to cause a greater degree of "perspiration wetness" than occurs with fabrics of wholly natural fibers₁. Additionally, there is a growing volume of literature demonstrating the survival and growth of microorganisms in textiles and their dissemination as a health risk_2,3,4,5.

While several bacteriostatic textile finishes already exist for personal wear, their use for this purpose has not gained ready acceptance. Poor activity against mold and mildew, lack of wash durability, inadequate safety data to meet current requirements, or a combination of these factors has hampered their use. Consequently, a safe, wash-resistant textile finish capable of inhibiting the growth of both bacteria and fungi is required.

For several decades, alkoxysilanes have been widely used by a variety of industries as coupling agents to bind and reinforce substrates. E. Plueddemann₆ has reviewed their use for such purposes. M. Latlief et al. have described the bacteriostatic action of quaternary ammonium compounds on textiles_7,8,9. The latter compounds exert their influence external to the microorganism by disruption of the delicate cell membrane and therefore do not need to be absorbed in solution to produce their bacterial killing. The combination of these technologies (that is, the bonding power of "quats" on a substrate such as textiles) should result in a durable, safe, antibacterial treatment and does so with AEM 5700 Antimicrobial Agent (3-trimethoxysilylpropyldimethyloctadecyl ammonium chloride, now known as GIS Microbe Shield or AEM 5700 Antimicrobial Agent). An unexpected benefit to the binding of this organosilicon quaternary to a wide variety of substrates is the increase in spectrum of both antibacterial and fungal killing power₁₀.

This report describes the practical utility of Dow Corning 5700 Antimicrobial Agent (now AEM 5700 Antimicrobial Agent) on BIOGUARD_* socks as a representative textile. Laboratory studies were conducted to measure the effectiveness of socks commercially treated with the AEM 5700 Antimicrobial Agent against odor-causing bacteria isolated from the foot. In-use clinicals were also conducted to measure actual reduction in foot odor on textiles treated with the AEM 5700 Antimicrobial Agent.

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In Vitro Microbiological Studies:   

       
The normal bacteria found on the skin of humans are capable of producing characteristic foul odors, especially on the foot and in the auxiliary region_{1, 11}. In order to obtain a sampling of normal bacteria on the foot, untreated 75 percent ORLON_**/25 percent nylon socks were worn by laboratory personnel during a routine workday, removed at home, sealed in plastic bags, and returned to the microbiology lab the following day. The bacteria were extracted from the socks in a liquid growth medium, isolated, and identified. The bacterial isolates obtained in the study are listed in Table I.

The bacteria represent a spectrum of Gram negative organisms capable of producing odors on textiles in contact with the skin. Figure 1 shows the correlation of increase in odor with increase in bacterial isolates.

Once the odor-causing bacteria were isolated, it was necessary to determine if treatment with the AEM 5700 Antimicrobial Agent would inhibit the growth of these microorganisms on the socks. ORLON/nlon socks treated with AEM 5700 Antimicrobial Agent were supplied by Burlington Socks/Adler_*. The socks were tested against each of the bacterial isolates from the foot according to AATCC Test Method 100-1977₁₂ modified to onclude 0.1 percent trition X-100 in a saline inoculom. The results of this testing are presented in  Table II.

The socks treated with AEM 5700 Antimicrobial Agent were effective in inhibiting the growth of the odor-causing bacteria on the sock.

A biostatic finish on a textile such as a sock must be durable to repeat home laundering if the benefit of the treatment is to be realized for the life of the article. Table III shows the antimicrobial activity of BIOGUARD socks following repeated laundering.

The antimicrobial activity of the treated socks was not reduced after 40 laundering cycles. Treated socks were machine washed through ten cycles in various laundry detergents used in the home. Residual antimicrobial activity was measured. The wash durability results using different detergents are presented in Table IV.

The antimicrobial finish applied to the socks was durable for ten laundering cycles in all of the detergents tested.

The in vitrotests indicated that socks treated with AEM 5700 Antimicrobial Agent do have a durable antimicrobial finish. To study the practicality of inhibiting the growth of odor-causing bacteria on socks under actual use conditions, an in vivoorganoleptic test was completed.

In Vivo Organoleptic Evaluation:

 
Burlington Socks/Adler supplied untreated ORLON/nylon control socks and socks treated with AEM 5700 Antimicrobial Agent to an independent test laboratory_* to compare the odors of socks following normal wear by male panelists. The socks included unwashed and washed (ten laundry cycles) control and treated socks.

The male panelists were each given a control and treated sock daily during the test period. Each sock was to be worn on a specific foot. At the end of a workday, panelists reported to the lab to remove the socks, seal them in plastic bags, and receive socks for the next day. Odor evaluations were made by four odor judges 14 hours after removal of the socks on each test day. Individual scoring sheets were used by the judges and new sheets were used every day of the evaluation. The odor grading scale was 0 to 10 ("no odor" to "very intense and disagreeable odor").

Two-day average odor scores were used to compare unwashed treated and control socks to washed treated and control socks. The Wilcoxon matched pairs test indicated that there was no difference in odor scores between the unwashed treated and control socks at the 95 percent confidence level.

There was a significant reduction in odor of washed treated socks compared to washed control socks at the 99 percent significance level. The difference in results between washed and unwashed treated socks when compared to controls is explained by the presence of nonsubstantive process chemicals such as dye carriers, softeners and wetting agents which are removed upon washing. The presence of these chemicals may:

Impart a hydrophobic character to the socks which inhibits intimate contact of microorganisms with the textile surface, thus reducing effectiveness. Impart a pleasant, new-clothing odor which can mask unpleasant odors and is similar in action to a deodorant.

Impart a temporary, leachable antimicrobial activity, usually due to the quaternary nature of most textile finishes such as softeners and antistats.

The results of this comparative evaluation show that AEM 5700 Antimicrobial Agent is bonded to the textile (sock) and is not removed by repeated laundering. In contrast to untreated controls, repeated washing does not destroy the antimicrobial activity nor ordor reduction of the treated socks.

Application of Antimicrobial Agent on Other Textiles:

  
Microbiological evaluations have been completed on a variety of other textiles treated with AEM 5700 Antimicrobial Agent such as those listed in Table V.

The fabrics include a diverse spectrum of fiber types and blends. They were treated against a broad spectrum of microorganisms including odor-causing bacteria, and bacteria and fungi which cause rot and mildew. In all cases, the treated textiles exhibited inhibition of growth of the microorganisms on the fabric, thus preventing rot and mildew, and reducing the production of foul odors.

Conclusion:

Chemical bonding of an organosilicon quaternary ammonium compound to textile substrates results in effective reduction of odor-causing microorganisms under actual in-use conditions of wear. Effectiveness is not reduced by laundering.

Tables:

Percent bacterial reduction as measured against an untreated control sock.

Percent bacterial reduction as measured against an untreated control sock.

Percent bacterial reduction as measured against an untreated control sock.

References:

1).Radford, P.J., American Dyestuff Reporter, November, 1973, p. 48-59.

2).Anderson, K.F., and Sheppard, R.W., Lancet, Vol. 1, 1959, p. 514-515.

3).McNeil, E., and Greenstein, M.,Chemical Specialties Manufacturing Association Proceedings, 1961, p. 134-141.

4).McNeil, E., Developments in Industrial Microbiology, Vol. 5, 1964, p. 30-35.

5).Wiksell, J.C., Pickett, M.S., and Hartman, P.A., Applied Microbiology, Vol. 25, 1973, p. 431-435. 6).Plueddemann, E.P., Journal of Adhesion Vol. 2, 1970, p. 184-201.

7).Latlief, M.A., Goldsmith, M.T., Friedl, J.L., and Stuart, L.S., Journal of Pediatrics, Vol. 39, 1951, p. 730-737. 8).Latlief, M.A., Goldsmith, M.T., Friedl, J.L., and Stuart, L.S., Journal of Pediatrics, Vol. 40, 1952, p. 324-329. 9).Latlief, M.A., Goldsmith, M.T., Friedl, J.L., and Stuart, L.S., Journal of Pediatrics, Vol. 40, 1952, p. 599-605. 10).Isquith, A.J., Abbott, E.A., and Walters, P.A., Applied Microbiology, Vol. 24, 1972, p. 859-863. 11).Tachibana, D.K., Annual reviews of Microbiology, Vol. 30, 1976, p. 351-375. 12).Technical Manual of The American Association of Textile Chemists and Colorists, Vol. 53, 1977.

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