**2.1 Effect of fibers**

236 Woven Fabrics

It is no doubtful that the hand judgement of fabrics is one of the important fabric tests and has been used widely by many people that can be classified as experts in textile factories and general consumers. The experts in factories especially in finishing departments carry out this judgement to control the property of their products every day. On the other hand each of the consumers also examines the property of the fabric by his "hand" to select a good clothing material according to his feeling and experience during purchasing (Kawabata, 1980). In both cases, fabric hand is examined mainly by the sense of touch and the sensory signals sent to the brain are formulated and clustered as subjective perception of sensations

Tactile sensations: prickly, tickling, rough, smooth, craggy, scratchy, itchy, picky, sticky.

 Thermal sensations: cold, chill, cool, warm, hot (Bishop, 1996; Dhinakaran et al., 2007). Fabric handle is a complex parameter and is related to the several fabric properties such as flexibility, compressibility, elasticity, resilience, density, roughness, smoothness, surface friction and thermal characteristics (Ozcelik et al., 2007, 2008). Fabric properties mostly influencing fabric handle are generally listed as fabric smoothness (28%), softness (22%), stiffness (8%), roughness (7%), thickness (5%) and weight (5%). Such fabric properties like warmth, hardness, elasticity, creasing propensity, drape and other properties less influencing the textile hand enter the residual part of 25% (Bishop, 1996; Grinevičiūtė et al.,

This chapter presents one of the most challenging properties of the textile materials, "the sensorial comfort" in detail. The first part deals with the factors influencing the fabric handle, such as fiber, yarn and fabric properties and finishing treatments. The second part of the chapter summarizes the mechanical properties related with the sensorial properties such as bending, shear, tensile, thickness and compression, drape, friction and roughness as well as other fabric sensory properties related to the assessment of fabric handle and quality such as fabric thermal properties, surface appearance, prickle, noise and odour. In the third part, subjective evaluation methods, systems and devices for the objective measurement of fabric handle are examined. Finally, the relationship between the subjective evaluation and

In textile products the basic elements that can fundamentally affect fabric handle are given below. All these characteristics have an interacted relation in terms of the mechanism of influencing sensorial comfort of the end product. Namely, yarn handle characteristics are the results of the fiber properties and similar relationship can be observed between yarn and

Fiber characteristics: Material type, morphological structure, fineness, length, friction

Yarn characteristics: Yarn type (staple fiber, continuous filament, textured), linear

 Fabric characteristics: Production method (woven, knitted, non-woven), fabric construction, weight, thickness, surface roughness, structure, yarn density etc.

 Moisture sensations: clammy, damp, wet, sticky, sultry, non-absorbent, clingy. Pressure (body fit) sensations: snug, loose, lightweight, heavy, soft, stiff.

as follows:

2005).

fabric features.

density, twist etc.

objective measurement of fabric handle is given.

property, resilience, compressibility etc.

**2. Factors influencing the fabric sensorial comfort** 

The fiber type (natural/man made, staple/filament) is the first criterion for obtaining various fabrics having diffferent sensorial comfort characteristics.

Linen is a fiber that gives fabrics comparatively higher toughness. 100% linen fabrics offer the highest tensile resilience, bending rigidity and bending hysteresis, whereas the lowest values are obtained in terms of the shear rigidity and shear hysteresis values. Cotton, viscose and cotton/linen, viscose/linen blended fabrics give comparatively lower surface friction, surface roughness and bending rigidity compared to 100% linen fabrics. (Behera, 2007). The surface properties of the yarns and fabrics are affected by the morphological properties of the animal fibers (Supuren, 2010). As the fiber diameter increase, the prickliness of the fabrics increases for this type of fabrics (Behera, 2007). Linen is a fiber that gives the fabrics comparatively higher toughness; the toughness is reduced by blending the fiber with viscose. 100% linen fabrics offer the highest tensile resilience, bending rigidity and bending hysteresis, whereas the lowest values are obtained in terms of the shear rigidity and shear hysteresis values. Cotton, viscose and cotton/linen, viscose/linen blended fabrics give comparatively lower surface friction, surface roughness and bending rigidity compared to 100% linen fabrics (Behera, 2007). The surface properties of the yarns and fabrics are affected by the morphological properties of the animal fibers (Supuren, 2010). As the fiber diameter increase, the prickliness of the fabrics increases for this type of fabrics (Behera, 2007).

The finer the fibers are, the smoother and more flexible the yarn is and the fabric drape gets better. Longer fibers and smaller variation in the fiber length distribution result in smoother yarn and fabric surfaces. Micro denier filament fabrics give a better drape and handle properties compared to the normal denier filament fabrics (Behera et al., 1998).

The cross-sectional shape of the fiber affects the smoothness and bending of the yarn (Shanmugasundaram, 2008; Behery, 2005). It also determines how light interacts with the fiber. For example, a round fiber will appear more lustrous than a trilobal fiber made of the same polymer (Behery, 2005).

Another property that is important for fabric handle is the fiber friction. The fiber–fiber friction influences the way that the fibers interact with each other. The friction properties affect the flexibility of the yarns. As the fiber–fiber friction increases, the ability of the fibers to slide from each other during yarn and fabric deformation decreases (Behery, 2005).

Besides the typical mechanical methods to alter the handle of fabrics/fibers, handle can be improved by by chemical treatments. In treating the fiber surface, chemicals called 'softeners' are usually used. Softeners work by lubricating the surface of the fiber. This reduces the fiber–fiber friction, which makes the fabric move and flow more easily. Another method of changing fiber hand is to alter the chemical nature of the fibers themselves. A very common method is the mercerization of cellulose. As cellulose is mercerized, the overall shape of the fiber becomes more circular and more uniform than its irregular form thus becoming stronger and smoother to touch. With its round shape, mercerized cellulose becomes more lustrous (Behery, 2005).

Sensorial Comfort of Textile Materials 239

The handle of the fabrics is affected by mainly fabric structure and fabric geometry. Fabric construction and yarn densities play major role in determining fabric handle (Shanmugasundaram, 2008; Na & Kim, 2001). Variations in warp and weft densities and in the number of warp and weft yarns have significant effects on the handle characteristics of the fabrics (Shanmugasundaram, 2008). Sensory analysis shows that fabric hand can be influenced more by fabric weave than by the component yarn. Weaves that use fewer yarn interlacing improve the handle characteristics of the fabrics (Behery, 2005; as cited in Vohs et al., 1985).

Fabrics for which the warp and weft twist are unidirectional (Z & Z twist direction) perform higher shearing rigidity, (smooth rounded curvature) in comparison to those for which the

The tightness factor of the knitted fabrics is another factor affecting the handle, with the increment of this factor, stiffness, which is related to bending rigidity, increase. Fullness, softness and smoothness decrease with the higher tightness factor (Park & Hwang, 2002).

Nonwoven fabrics differ from knitted or woven fabrics, because they are not based on webs of individual fibres, which can be bonded to each other by several means that changes the texture ranges from soft to harsh. Fiber composition influences performance far more for nonwoven fabrics than for fabrics containing yarns. High strength combined with softness is one of the most difficult property combinations to be achieved in nonwoven fabrics because the geometrical factors that permit high strength also lead to increased stiffness

There are many researches in the literature related with the effects of finishing process on sensational properties of the fabrics. The diversity of fabric types with finishes available for any end-use continues to increase, making the selection of the most appropriate fabric an

Different kind of end products can be produced from the same unfinished woven or knitted fabric by using various finishing treatments. High-speed scouring and milling create a fibrous surface as well as modifying other properties of the fabric, notably shear rigidity and specific volume. Heat treatments may cause fibres to crimp, increasing the bulkiness of the fabric. Soft handle and in some cases the 'peach skin' effect can be obtained by enzymatic treatment. By using cellulose enzyme, which acts on the fibril ends and causes their shortening, a slight pick-out surface can be obtained. Light brushing is another mechanical treatment that gives peach-skin effect to the fabrics. Raising and teaseling are the mechanical processes which draw fibres to the surface of a fabric to create a pile. Calendaring and also many chemical treatments (softening compounds, resins) give flatter surface that affect the fabric hand. Pressing and decatising are designed to flatten the fabric and create a smooth surface. Cropping and singeing are the processes which are designed to remove fibrous protrusions from the body of the fabric and thereby create a smooth surface. After the process of flame-retardant finishing, the stiffness parameters, especially bending and shear properties, increase significantly (Le et al., n.d., as cited in Stewart & Postle, 1974; as cited in

Boos, 1988; Shanmugasundaram, 2008; Mamalis et al., 2001; Frydrych et al., 2002).

warp and weft twist directions are opposite to each other (Yazdi & Özçelik, 2007).

**2.3 Effect of fabrics** 

(Shanmugasundaram, 2008).

increasingly difficult task (Shanmugasundaram, 2008).

**2.4 Effect of finishing** 

Crystallinity also affects the handle of the fabrics by influencing the way that the fibers move and respond to bending. If the molecules in a fiber are aligned along the fiber axis, the fiber will be strong in uniaxial tension along the fiber axis. A more crystalline fiber is more resistant to bending (Behery, 2005).

### **2.2 Effect of yarns**

The twist of the yarns which the fabrics are made of, is one of the main parameter affecting the fabric behaviour including bending, stiffness and shearing property (Shanmugasundaram, 2008). The amount of twist, together with the characteristics of the fibers (luster, hand, cross-sectional shape, etc.), determines the appearance and feel of the yarn. Fabrics composed of yarns with higher levels of twist are known to have higher bending stiffness, less compressibility, less fiber mobility, lower surface friction, less bulkiness than similar fabrics composed of yarns with less twist. Increased yarn twist leads to greater internal (fiber-to-fiber) friction within the yarn structure and reduce softness and bulkiness, in general, and hairiness in the case of spun yarns (Behery, 2005).

Another factor affecting handle is the number of the yarns folded. In plied yarns, i.e. two or more single yarns twisted together, the stiffness is increased compared to single yarns (Shanmugasundaram, 2008).

Filament yarns are sometimes put through an additional process known as texturizing. The process modifies the handle of the filament yarns by adding bulkiness and/or stretchiness to the filaments and therefore changes the smooth surface feel of fabrics (Behery, 2005). The feel of textured-yarn fabrics against the skin is considerably different than that of flat-yarn fabric. Textured yarns give a fabric more pleasant hand, fabric becomes warmer and softer and it has less synthetic feeling (Shanmugasundaram, 2008; as cited in Mahar & Pestle, 1983).

Fiber linearity and fiber-packing density in yarn structures are also important for the tactile qualities of a fabric, when not masked by twist (Behery, 2005). Comparing multifilament yarns of the same size and fiber composition, yarns containing more filaments (finer) are much less stiff than multifilament yarns containing less filaments (coarser). Fabrics produced from coarser filament textured yarns have higher thickness, compression characteristics than that of the fabrics made of finer filament textured yarns but there is no significant difference in fabric recovery and resiliency (Mukhopadyhay et al., 2002).

Yarn type has a significant effect on the handle properties of the fabrics. The static friction coefficient of cotton fabrics made of combed ring spun yarn is much lower than that for fabrics made of rotor yarn due to the more regular, denser and smoother structure of the ring spun yarn compared to the rotor yarn, on the surface of which there are visible wrapped fibers. The plain weft knitted fabric produced from the sirospun yarn is thicker, softer, of poorer recovery from compression, less rough and less stiff. For finer sirospun yarn, the shape retention is worse as the hysteresis of bending and shear is greater. (Sun & Cheng, 2000). Air-jet spun yarns produce thicker, less compressible, more extensible and stiffer fabrics than fabrics made from ring spun yarns (Behery, 2005; as cited in Vohs et al., 1985).

The fancy yarn structure also influences the subjective handle properties of the fabrics. In the production of fancy yarns, as the feeding rate increases; the fabric thickness, fabric weight, bending rigidity and friction coefficient of the fabric increase (Özdil et al., 2008).
