Bamboo fibres have good antimicrobial properties, which make it more suitable for not only socks but also for other clothing like innerwear, affirm C Gomathi and M Manoharan.

Microbial infestation poses danger to both living and nonliving matters. Obnoxious smell from the inner garments such as socks, spread of diseases, staining and degradation of textiles are some of the detrimental effects of bad microbes. Bamboo fibre clothes have actually been showing up in department stores and women's boutiques. Bamboo is now being made into a fibre that has wonderful characteristics. Bamboo fibres are the newest thing to hit the textile arena. An exclusive manufacturing process makes it possible to create a heavily breathable, absorbent samples entirely from bamboo fibre.

Bamboo fibre has particular and natural functions of anti-bacteria, bacteriostasis and deodorisation. It is validated by Japan Textile Inspection Association that, even after fifty times of washing, bamboo fibre samples still possess excellent function of antibacteria, bacteriostasis. Its test result shows over 70% death rate after bacteria being incubated on bamboo fibre samples. Bamboo fibre's natural antibacteria function differs greatly from that of chemical antimicrobial. The latter often tends to cause skin allergy when added to apparel.

This article deals with the antimicrobial behaviour of bamboo fibres with the use of socks.

This report deals with a study to assess the antibacterial and antifungal properties of socks made out of bamboo fibres compared with those made from cotton, viscose and 50/50% bam/cot (before and after wear of socks).

The inherent properties of the textile fibres provide room for the growth of micro-organisms. Besides, the structure of the substrates and the chemical processes may induce the growth of microbes. Humid and warm environment still aggravate the problem. Infestation by microbes cause cross infection by pathogens and development odour where the samples is worn next to skin. In addition, the staining and loss of the performance properties of textile substrates are the results of microbial attack. Basically, with a view to protect the wearer and the textile substrate itself bamboo textiles is quickly emerging trend in the fashion world.

Bamboo in textiles

Bamboo textiles have many fantastic properties that in combination make this a truly amazing product. It is breathable and cool, has a nice lustre; extremely soft with fast water absorption performance; and antibacterial. Because the cross-section of bamboo fibre is filled with various micro-gaps and micro-holes, bamboo cloth has much better moisture absorption. Bamboo cloth can quickly absorb and evaporate human sweat. Bamboo cloth is an indulgence with its wonderful silky softness. Bamboo cloth is naturally antibacterial. Bamboo samples successfully avoid pilling and shrinkage problems.

Bamboo fibres are quickly emerging now in the fashion world. The samples woven with bamboo yarn are light, almost translucent, and softer than cotton.

It has a natural sheen that feels like silk or cashmere, but has the advantage of being machine-washable. This natural fibre is hypoallergenic, absorbent and fast-drying. It is naturally antibacterial and will not hold odour. Like other natural fibres, it allows the body to breathe as the samples absorb the sweat from the body. It is also the most sustainable of the natural fibres. Because of its natural antibacterial properties, it needs no pesticides. It is also 100% biodegradable.

Bamboo cloth is still not widely known, but considering these benefits, there is a considerable and growing market for bamboo products.

What are microbes?

Microbes are the tiniest creatures not seen by the naked eye. They include a variety of micro-organisms like bacteria, fungi, algae and viruses. Bacteria are unicellular organisms, which grow very rapidly under warmth and moisture. Further, sub divisions in the bacteria family are Gram positive (Staphylococcus aureus), Gram negative (E. coli), spore bearing or non spore bearing type. Some specific types of bacteria are pathogenic and cause cross infection. Fungi, molds or mildew are complex organisms with slow growth rate. They stain the samples and deteriorate the performance properties of the samples. Fungi are active at a pH level of 6.5.

Algae are typical micro-organisms which are either fungal or bacterial. Algae require continuous sources of water and sun light to grow and develop darker stains on the samples. Algae are active in the pH range of 7.0 - 8.0. Dust mites are eight legged creatures and occupy the household textiles such as blankets, bed linen, pillows, mattresses and carpets. The dust mites feed on human skin cells and liberated waste products can cause allergic reactions and respiratory disorders.

Socks construction details

Yarn count - 30's

Knit Structure - Flat Knit (Single Jersey)

Size - 9 to 11

Cylinder - Double Cylinder

Diameter - 4 Needles - 168

Weight (Socks) - 0.015gm

Procedure

100% Bamboo

100% Cotton

50/50% Bam/Co

100% viscose

Knitted socks were bleached by using bleaching recipe. Then microbial tests were conducted. Then microbial growth of bamboo socks was compared with those made from 100% cotton, 100% viscose & 50/50% bam/cot.

Test methods

Survivability of bacteria

To find out how samples are able to resist survivability of bacteria, a samples swatch survival test was carried out using two test organisms (Escherichia coli and Staphylococcus aureus). Starting from 24 hours to 120 hours of incubation, the survival of known test bacterial concentration in all the four samples was assayed over time, every 24 hours. Survival test was also carried out using worn socks.

Survivability of fungi

To find out how samples are able to resist the survivability of fungi, samples scratch survival test was carried out using two test organisms (Aspergillus niger and Trichoderma viridae). Starting from 48 hours to 360 hours of incubation, the survival of the known fungi in all the 4 samples was assayed over a constant period of time, every 24 hours.

The growth rate and time course analysis were performed. Other validation tests such as AATCC 100, AATCC 147, AATCC 30 and soil burial test were also conducted to compare the antimicrobial activity in bamboo, cotton, rayon samples and 50/50% bam/cot. Odour evaluation test was also conducted.

Results & discussion

Test 1

Survivability of bacteria

To find out how the samples are able to resist the survivability of bacteria.

Test 1 was carried out to demonstrate the survivability of bacteria on four test samples after constant period of incubation with the standard inoculum at the start of experiment (Table 1 & 2). The results of test indicate that the survivability of bacteria on cotton was more lasting compared to rayon and bamboo. The survivability of bacteria on 50/50% bam/cot is similar to bamboo.

The general survivability of the test organism E. coli, was less compared to S. aureus. This analysis indicated that bamboo potentially resists the colonisation of both E. coli and S. aureus from the second day of incubation, which is an indication of bamboo's antimicrobial resistance characteristic.

TEST 2

Survivability of fungi

To find out how the samples are able to resist the survivability of fungi

Test 2 was carried out to demonstrate the survivability of fungi on the four test samples after constant periods of incubation with the standard inoculum at the start of experiment (Tables 3 & 4). Results indicate that the survivability of fungi was more or less the same on all the four test samples.

From this test, it can be concluded that the antifungal resistance of bamboo, cotton and 50/50% bam/cot are equally efficient, when compared with rayon. Generally, all the four samples supported the growth of T. viridae and resisted the growth of A. niger.

Test 3

Determination of rate of growth and comparison between four samples.

The growth rate of bacteria (E. coli and S. aureus) and fungi (T. viridae and A. niger) were compared when grown on the four test samples as substrates. The results are presented in Table 5. This test proves that the growth rate of organisms on bamboo as a substrate is less, when compared with cotton and rayon. The natural antimicrobial effect of bamboo does not allow the multiplication of bacteria and fungi and ultimately proves to be both bacteria static and fungi static. The growth rate of micro organisms on 100% cotton is same as rayon. On 50/50% bam/cot, the growth rate of organism is less when compared with cotton.

Determination of rate of growth and comparison between four samples

Test 4

Time course analysis to study the inhibitory effect of bamboo, rayon and cotton & 50/50% bam/cot samples towards microorganism

The inhibitory effect of bamboo, cotton, rayon and 50/50% bam/cot samples towards bacteria (E. coli and S. aureus) and fungi (T. viridae and A. niger) were compared based on a time course analysis and it was observed that E coli was able to survive, only up to 24 hours on bamboo and 50/50% bam/cot whereas on rayon it was able to survive for up to 120 hours. It was also observed that E.coli was able to survive for up to 72 hours on 100% cotton. It was also observed that S. aureus was able to survive on bamboo upto 48 hours and 50/50% bam/cot whereas on 100% cotton it was able to survive for up to 72 hours. It was also observed that S aureus was able to survive on rayon up to 120 hours.

Test 5

Other normal validation tests

AATCC standard tests such as AATCC 100, AATCC 147, AATCC 30 and soil burial test, were carried out. All the above tests confirmed that the antimicrobial effect was highest in the case of bamboo followed by 50/50% bam/cot, rayon and cotton.

Odour inhibition test

Tests for odour inhibition are done with a 'Bottle incubation method' using an artificial perspiration consisting of sodium chloride (2.5%), urea (1.2%) and lactic acid 85% (3.4%), potassium hydroxide (1.4%) and pH adjusted to 7.0 with ammonium hydroxide.

This solution is incubated with soil suspension (1 gm garden soil to 10 ml water, 1 ml suspension to 100ml artificial perspiration). The sample is incubated in 500 ml stoppered jar at 30o C.

The odour is judged subjectively by assessers after 1, 4, 8 and 11 days.

Conclusion

Based on the above in-depth analysis, it was observed that the bamboo has good antimicrobial properties followed by 50/50% bam/cot, rayon and cotton. The various tests carried out namely, rate of growth, survivability of bacteria and fungi, time course analysis of the inhibitory effect against microbes, normal AATCC procedures like AATCC 30, AATCC 100, AATCC 147 and soil burial test confirm that the antimicrobial effect of bamboo samples is comparatively of a higher order than 50/50% bam/cot, cotton and rayon. Results also show that there is no appreciable level of antimicrobial activity for cotton samples and it supports the growth of micro-organisms on it.

In the highlight of the above in-depth study and its findings, it is evident that the bamboo samples has got indigenous antimicrobial effect. This indigenous antimicrobial property of bamboo makes it more suitable for clothings such as innerwears & footwears such as socks as compared to cotton.

References

1. AATCC Technical Manual 2006, Antifungal Activity, Assessment on Textile Materials: Mildew & Rot Resistance of Textile Materials, AATCC.

2. Journal of Textile Association Jan-Feb 2007.

3. Vol 84. Feb.2004. IE Journal - TX.

4. SITRA - Research Report, Studies on Spinning Behaviour, Antifungal and Thermal Properties of Bamboo Fibres, Vol 51, June 2006.

5. SITRA - Research Report - Development of Bandages Using Bamboo Fibres, Vol 52, August 2007.

6. Colourage, September 2005.

7. Colourage, May 2006.

Webs:

1. www.bamboofabricsstore.com

2. www.bambooclothes.com

3. www.bambrotex.com

4. www.bambootextiles.com

5. www.tenbro.com

6. www.bambooresearch.com

7. www.indiantextilejournal.com

Note: For detailed version of this article please refer the print version of The Indian Textile Journal February 2009 issue.

C Gomathi,

Final Year MTech student Department of Textile Chemistry,

SSM College of Engineering,

Komarapalayam,

Namakkal District, Tamil Nadu.

Mr M Manoharan,

Asst Professor and Head Department of Textile Chemistry,

SSM College of Engineering,

Komarapalayam,

Namakkal District, Tamil Nadu.