Maintaining body heat under different environmental conditions is very essential for a fabric which determines its comfort level. A key performance criterion in this respect is the Moisture Management. The human body releases around 60ml of water vapour at ambient conditions even when it is at rest. When we do some activity like walking or play any sports, the body warms up and sweats more which is more or less absorbed by the textile material. This humidity needs to be transferred to the surface of the fabric for evaporation and thus producing a cooling effect. Therefore, to make a wearer feel comfortable, not only should the fabric evaporate the perspiration from the skin surface to the fabric surface but, the moisture should also get evaporated. Moisture adds weight to the garment and makes the skin cold. It can also cause irritation and skin diseases. Hence, it is very essential to have a moisture management fabric so as to make the wearer feel comfortable.


Aim

The main aim of moisture management fabric is to make the skin feel dry. In order to achieve this, humidity should be evaporated and transferred to the atmosphere as soon as possible. The transportation of humidity to the surface of the fabric is done by a capillary force known as wicking. As the gaps between the individual fibres becomes thin the force increases. Thus, finer fibres will have smaller gaps and better humidity transport. The evaporation of the humidity depends on the surface area of the textile used. As the surface increases, fibres are finer and hence more fibres at the surface and faster humidity evaporation.


Requirements of a moisture management fabric:

For a fabric to be a good moisture management fabric it needs to fulfil the following attributes according to (Dr. S. K. Chinta et al, Significance of Moisture Management for High Performance Textile Fabrics)

•   Optimum heat and moisture regulation

•   Good air and water vapour permeability

•   Rapid moisture absorption and conveyance capacity

•   Absence of dampness

•   Rapid drying to prevent catching cold

•   Low water absorption of the layer of clothing just positioned to the skin

•   Dimensionally stable even when wet

•   Durable

•   Breathability and comfort

•   Easy care performance

•   Lightweight

Moisture management route

Regarded as a second skin, the textile material should work synchronously and be compatible with the human body's heat regulation mechanism. Transmission of the moisture in both liquid and vapour form is equally important to make the wearer feel comfortable. In this regard, wetting, wicking and moisture vapour transmission are of critical importance. This transmission occurs by three mechanisms.


1.    Simple diffusion through inter yarn spaces: Controlled by the water vapour pressure gradient across the inner and outer faces of the fabric, this is the main mechanism for transferring the vapour in low moisture content conditions. The size and concentration of inter yarn pores and the fabric thickness governs the resistance to diffusion.

2.   Capillary transfer through fibre bundles: Wicking of the liquid water through the yarns takes place which is then evaporated at the outer surface. The efficiency of yarn working depends on the surface tension, i.e., wet ability of the fibre surfaces, and the size, volume and number of capillary spaces is determined by the choice of yarn and fabric construction.

3.   Diffusion through individual fibres: Depending on the hydrophobic or hydrophilic nature of the fibres, the water vapour is absorbed into the fibres at the inner surface of the fabric, diffused through the fibre structure and desorbed at the outer surface.

Developments in moisture management techniques


Several developments have taken place in the manufacture of moisture management fabrics. These include:


1.   Water proof breathable fabrics: They allow active ventilation yet prevent the penetration and absorption of liquid water. They may passively allow water vapour to pass through them.



2.    Spacer fabrics: In order to have an insulating and thermoregulatory effect, an intermediate layer of air is created by joining two separate fabric webs by spaces threads or fibres of varying rigidity mostly monofilaments thereby creating a 3D fabric. Low weight in proportion to the large volume is an advantage. These fabrics have an unlimited range of applications like healthcare, safety, military, automotive, aviation and currently used for functional clothing like sports shoes, knee and elbow protectors etc.



3.    Phase changing materials: Waxes like Eicosane, Octadecane, Nonadecane, Heptadecane and Hexadecane have the distinctive capacity to soak and emit heat energy without altering the temperature. Such materials are called Phase Change Materials (PCM). They accumulate and release heat energy and maintain their temperature range of 30-34 degree celsius when mixed in a microcapsule, which is comfortable for the body. When the temperature of the garment layers reaches the PCM transition temperature, PCM microcapsules create small, transitory heating and cooling effects in the garment layers.

 

4.    Pine cone effect: The smart fabric is constructed on the principle of the pine cone, a technology which offers a solution to the uncomfortable sensations caused by the moisture build up due to the changing temperatures. The pine cones which appear to be closed on the tree, opens and releases the seeds when it falls. The scales of the pines made of two layers of stiff fibres running in different directions open up. As it dries out the scales inside get expanded more than outside, making the outer scales to bend outwards and thereby releasing the seeds.



Applications of moisture management technique:

Following are the areas where the moisture management techniques are popularly applied:

•   Inner wears

•   Athletic wear (active sportswear)

•   Performance wear (climbing, walking, skiing)

•   Comfort wear (nightwear)

•   Military (multi-climate clothing)

•   Health (hospital bed linens, wound dressings)

•   Agricultural technology (Geo-textiles, greenhouse screening panels, soil moisture control)

•   Technical solutions (Formula 1 protective clothing, firefighting, industrial clothing)

•   Industrial (filter & valve technology, building, packaging)

•   Upholstery (transport)

Latest developments:

American Association for Textile Chemists and Colourists have approved a new test method 195 Liquid Moisture Management Properties of porous materials for the measurement, evaluation and classification of liquid moisture management fabrics suitable for measuring the performance of knitted, woven and non woven fabrics.

Based on water resistance, water repellence and water absorption characteristics of the fabric structure, including the fabrics' geometric and internal structure and the wicking characteristics of its fibres and yarns the test results are obtained.


Moisture management properties of a fabric are hence characterized by 10 moisture management indices namely,

1.    Wetting time top

2.    Wetting time bottom

3.    Top absorption rate

4.    Bottom absorption rate

5.    Top maximum wetted radius

6.    Bottom maximum wetted radius

7.    Top spreading speed

8.    Bottom spreading speed

9.    Accumulative one-way transport index

10. Overall moisture management capability (OMMC)

The performance of the fabric is assessed using a grading scale of 1-5 based on the above indices, where Grade 1 is poor and Grade 5 is excellent. The American Association of Textile Chemists and Colourists (AATCC) has developed and approved two new test methods for evaluating drying rates of fabrics. The drying performance of fabric can be analyzed by the following new methods.


AATCC Test Method 200-2013, Drying Rate of Textiles at their Absorbent Capacity Air Flow method: Vertical air flow passing through fabric mounted on a circular opening is used to determine the drying rate of textiles at their absorbent capacity under air flow conditions. AATCC Test Method 201-2013, Drying Rate of Fabrics Heated Plate Method: Horizontal air flow over the surface of a fabric while on a heated plate set at 37 C is used to determine the drying rate of a fabric exposed to a prescribed volume of water while in contact with a heated plate under air flow conditions. These new test methods simulate actual wearing conditions in which the fabric would be exposed to air flow and in contact with skin.

Conclusion

Moisture management play a key role in all sectors of textile application. Tailor made fabrics can be made to suit the specific end-use requirements. Due to the high-performance of the Moisture Management Fabrics, apparel manufacturers are shifting their attention in manufacturing moisture management fabrics especially in the sports textile area which strives to improve its functionality. The future will see further developments in the field of moisture management fabrics. The moisture management functional design of a clothing system can allow effective transfer of moisture and latent heat loss to keep the clothing dry and comfortable. Thus, the performance of protective clothing can be greatly improved if it is systematically designed. The water vapour permeability and moisture management of fabrics are indeed very important to prevent water condensation in the clothing and ultimately ensure improved superior thermal functional and comfort performance.


References:

1.    Dr. S. K. Chinta, Ms. Pooja D. Gujar, Significance of Moisture Management for High Performance Textile Fabrics, International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 3, March 2013.

2.    Product-industries-research.hktdc.com, Hong Kong Trade Development Council

3.    Dr. Petry, Textile Auxiliaries, Mositure Management.

4.    JUNYAN HU,Y I LI,KWOK-WING YEUNG,ANTHONY S. W. WONG, AND WEILIN XU, Moisture Management Tester: A Method to Characterize Fabric Liquid Moisture Management Properties, Textile Res. J. 75(1), 5762 (2005).

5.    Moisture Management and Wicking, Gunaseelan J. 

6.    S. X. Wang, Y. Li1, Hiromi Tokura, J. Y. Hu, Y. X. Han, Y. L. Kwok and R. W. Au, Effect of Moisture Management on Functional Performance of Cold Protective Clothing, Textile Research Journal Vol 77(12): 968980.

7.    Dr. S. K. Chinta, Ms. Pooja D. Gujar, SIGNIFICANCE OF MOISTURE MANAGEMENT IN TEXTILES, International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 6, June 2013.


Image courtesy:

1. Torayentrant.com

2. Plagiocephalyflathead.com

3. Tchester.org


About the author: Ayodya Kavitha is an assistant professor in the University college of Technology. N. Giribabu is a Textile Consultant and Salwa Rasheed, B.Tech also works in the University College of Technology.