**4.2. Comfort characterizations**

several limitations of using *in vivo* measurement techniques. Especially, when comparing different padding performance on a leg, there exist unavoidable variation in application techniques and varying limb movement. Moreover, the location of pressure sensor at the critical sites especially over bony prominence is highly unstable, which may cause unnecessary noise or experimental error. The above facts indicate the need for a simple or alternative

Compression load-recovery test is common to obtain the energy absorption ability of a nonwoven material. An Essediel thickness tester was used for measuring compression characteristics of textile materials (Figure 3b). The specimen was placed on a flat surface, and the transverse weight was applied using a pressure foot (20 mm diameter). The compressive pressure was increased from 20 to 200 kPa by applying additional dead weights during the compression cycle, and similarly in recovery the pressure was decreased in steps. The thicknesses were measured at different compressive loads during compression and recovery cycles. The initial thickness *To* was taken for the initial pressure *Po* (~2 kPa), which was due to weight of the pressure foot without any applied external load. The works done during compression and recovery process can be obtained from the plot of thickness versus compres‐ sive pressure (Figure 6). These calculated energies can be further used to characterise padding

**Figure 3.** a) A simple prototype for the pressure measurement using Kikuhime® pressure sensor; b) An Essediel thick‐

method to obtain pressure absorption ability of padding.

170 Non-woven Fabrics

performance as discussed in detail in the next section.

ness tester for compression-recovery test

Thermo-physiological wear comfort and skin sensational wear comfort are two main aspects of wear comfort of any clothing [31]. The first one concerns the heat and moisture transport properties of the fabric, while the latter one deals with the mechanical contact of the fabric with the skin, its softness and pliability in movement and its lack of prickle, irritation and cling when damp. The main properties of the fabric that influences the thermal comfort are: air permeability, water or moisture vapour permeability/transportation and heat transmission [36]. Air permeability is a measure of how well a fabric allows the passage of air through it. It is expressed as the volume of air (in cc) that passes in 1 s through 1 cm2 of fabric under a pressure head of 1 cm of water. Figure 4a shows the photograph of a TEXTEST Air Permeability Tester (FX3300) to measure the air permeability at a standard atmosphere of 98 Pa. Similar to air permeability, the moisture vapour transmission indicates the breathability of the textile to allow water vapour to pass out from the skin surface through the textile. This is expressed as the steady water vapour flow in unit time through unit area of body, normal to specific parallel surfaces, under specific conditions of temperature and humidity at each surface. Figure 4b shows a Moisture Vapour Transmission Tester (Model CS-141), which offers an easy and fast method to obtain the moisture vapour transmission rate. Thermal comfort is related to the fabric's ability to maintain skin temperature and allow transfer of perspiration produced from the body. For the evaluation of thermal comfort, a very simple instrument Alambeta (Sensora) is available, which can measure thermal characteristics of textile such as thermal resistance, thermal conductivity and thermal absorptivity (Figure 4c).

**Figure 4.** (a) TEXTEST air permeability tester; b) moisture vapour transmission tester (Model CS-141); c) Alambeta (Sensora) for heat transmission

Apart from the above-mentioned comfort properties, liquid transport behaviour of padding is also critical. This helps in removing body fluids or exudates from the wounded portion to prevent excess moisture build-up that causes irritation or discomfort to the wearer. The measurement of fluid transport is essential to understand how padding behaves on interaction with the fluids and what should be ideal structure for the nonwoven to obtain more spreading of body fluids to promote faster evaporation or removal. Several vertical and in-plane wicking tester are available that can be used for easy assessment [37-41]. Vertical wicking is determined by measuring the wicking height against gravity for a hanging fabric. An in-plane wicking deals with the transport behaviour in the horizontal plane of the fabric and describes several useful parameters such as the liquid flow anisotropy, the rate of movement, and the area of wet surface with time. Figure 5 shows the photograph of the computerized wicking tester for in-plane transport measurement [41].

**Figure 5.** Photograph of the instrumental set-up for measuring in-plane wicking
