**6. Evaluation of antimicrobial finishes**

The AATCC Technical Manual12 has a number of test methods that are useful for evaluating antimicrobial finishes on textiles. These tests are summarised in Table 1. Two types of antimicrobial tests are dominant, the agar-based zone of inhibition tests and the bacteria counting tests. The relatively new ISO/DIS 20645 and the corresponding EN ISO

Textiles with biostatic properties, however, are subject to fewer regulations. The actual mechanisms by which antimicrobial finishes control microbial growth are extremely varied, ranging from preventing cell reproduction, blocking of enzymes, reaction with the cell membrane (for example with silver ions) to the destruction of the cell walls and poisoning the cell from within. In Figure 11 and 12 the chemical structures of some of antimicrobial

agents are shown.

Fig. 12. Bound antimicrobials

4. colourless and odourless;

12. no environmental problems.

chemicals;

2. durable for the life of the product;

It is fairly easy to list the desirable properties of an 'ideal' biocide: 1. wide spectrum of effectiveness against both bacteria and fungi;

5. reasonable cost, and effective at low concentrations; 6. resistant to leaching, weathering and sunlight;

11. withstands processing conditions and temperatures;

10. applicable using standard textile machinery;

**6. Evaluation of antimicrobial finishes** 

3. non-toxic to humans at concentrations used – safe to handle and use;

7. no adverse effect on handle or other physical properties of the fabric;

9. does not accelerate or catalyse other degenerative processes;

8. compatible with water-repellent and flame-retardant finishes, dyes and other textile

The AATCC Technical Manual12 has a number of test methods that are useful for evaluating antimicrobial finishes on textiles. These tests are summarised in Table 1. Two types of antimicrobial tests are dominant, the agar-based zone of inhibition tests and the bacteria counting tests. The relatively new ISO/DIS 20645 and the corresponding EN ISO

**5. Practical biocides** 

20645 are based on the agar diffusion test and ISO 11721 is a burial test (part 1 for the determination of an antimicrobial finish and part 2 for the determination of the long-term resistance). The main difficulties of these tests are mostly poor reproducibility of the test results and often insufficient correlation between laboratory results and actual conditions in the field. Careful attention to detail and trained laboratory personnel are essential for accurate and repeatable results from these methods.( Schindler & Hauser, 2004)

A more rapid test method, developed by the British Textile Technology Group in the late 1980s, is based on adenosine triphosphate (ATP) luminescence. The growth of microorganisms is assessed by firefly bioluminescent detection and ATP analysis.3


Table 1. Comparison between different AATCC test methods

Antibacterial Agents in Textile Industry 405

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