Humectabilidad de telas de poliéster

Hydrophilising Agents to Impart Comfort Properties to Synthetic Fabrics
By Dr Naresh M. Saraf, Dr Geeta N. Sheth and Dr A.G. Sabale, of Sarex Overseas, India
Introduction
FITNESS IS the buzzword of modern-day youth. They are always looking for the hottest trends in clothes and accessories, which provide aesthetic appeal and, at the same time, the required comfort properties. Synthetic textileshave innumerable advantages, including cost, durability and flexibility, but they suffer in comparison with cellulosic material on hydrophilicity. Polyester and polyamide fabrics have limitations on sweat absorption and evaporation. Hence, there is a need to develop hydrophilising agents for synthetic textiles, to provide comfort properties. Figure 1 shows the energy balance of the body whenexposed to the environment. It produces a lot of heat during a workout and this could cause the core temperature to rise above 37°C, but the body tries to regulate the temperature via perspiration and evaporative cooling. Clothing can act as an unwanted buffer in the moisture-transfer or moisturemanagement process.

Moisture Management
The term ‘moisture management’ always refers to the transportof moisture vapours and liquid away from the body (Figure 2). Today, this is just one aspect of the concept of ‘wearer comfort’, as the feel of the fabric against skin may include various descriptors, such as clammy, prickly, stiff or dry, etc. In the case of cotton, the hydrophilicity of the fibre itself wicks away the moisture, which passes through the openings in the fibres or yarns, wheredistinctly accelerated evaporation takes place, resulting in comfort for the wearer. On the other hand, clothing made up of synthetics such polyester or polyamide, etc, is unable to wick away the moisture/perspiration due to their inherent hydrophobic nature, so the fabric tends to stick to the skin. This impairs the comfort, which is a function of a fit garment. To maximise comfort and to feel cool insynthetic garments, the fabric must allow liquid to wick on to the surface, spread away and evaporate quickly. Here, the wicking simply means the

Figure 2: Mechanism of wicking away perspiration from skin

Figure 1: Energy Balance of the Human Body

capillary movement of moisture within the fabric structure and moisture management is nothing but the controlled movement of water vapour andliquid water (perspiration) from the surface of the skin to the atmosphere, through the fabric. Wicking rate is measured by a ‘strip’ test, in which a fabric strip is suspended vertically, with its lower end immersed in a reservoir of water containing red dye. The elapsed time for water to reach a certain height is recorded. The data measured by this method is reproducible. Hydrophilisingproperties are, in addition, measured by a ‘drop test’, and the diameter of the drop and time is measured as a function of spreading. In this method, water droplet is placed on the fabric and the time taken for the droplet to wick into the fabric and disappear is measured. As moisture-management properties are an important value-added element of clothing fabrics, it is necessary to impart thehydrophilicity to synthetics such as polyamide and polyester. Based on the need and demand of the consumer, Sarex has developed

APRIL 2009

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Technical Briefing: Polyester

hydrophilising agents such as Sarasoil-X, Coolcot Dry and Geotex-HPA for polyester and polyamide. Some of these finishing agents not only impart hydrophilicity but also improve the soil-release and antistatic properties.Moisture Management Finish from Sarex
Finishing with Sarasoil-X, Coolcot Dry and Geotex-HPA on polyamide and polyester fabric can be carried out by conventional methods and it does not require any new machines or special modifications. Finishing with above products was carried out on polyamide and polyester fabric. Products were applied in concentrations of 20–30g/l by padding at 65 to 70%...