**2. General properties of microfibers**

Potentially, any man-made fiber could be made into a microfiber (Smith, n.d.). Microfibers are most commonly found in polyester and nylon (Smith, n.d.; Purane & Panigrahi, 2007; Anonymous, 2000). Trevira Finesse, Fortrel Microspun, DuPont Micromattique and Shingosen are all trade names for various polyester microfibers, whereas Supplex Microfibre, Tactel Micro and Silky Touch are some of the trade names for nylon microfibers (Mukhopadhyay & Ramakrishnan, 2008). Nylon is claimed to have advantages over polyester in having a better cover, plus lower density, higher strength and abrasion resistance. Polyester is easier to spin and is available in finer filaments than nylon. Polyester raised fabrics are easier to produce. This has given polyester an economic advantage in apparel and sportswear markets (Anonymous, 2000). However, micro-denier versions of rayon, acrylic and polypropylene products are available to consumers (Purane & Panigrahi, 2007; Smith, 2011; Anonymous, 2000). Microfibers can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, viscose and silk (Smith, n.d.; Anonymous, 2000). This enhances the appearance, hand, drape and performance properties of the fabrics (Basu, 2001).

Ultra-fine fibers were produced in the late 1950s which were not of continuous filament type but were fine staple fibers of random length and found no application except for being processed into nonwoven sheets immediately after spinning. In 1961 a petal-shaped ultra fine filament type fiber described in a patent was probably the first example of a potential ultra-fine filament. Another patent issued simultaneously described splitting two component conjugate fibers of non-circular cross section into the two separate components after weaving. No attention was paid at that time for combining these technologies to produce ultra-fine fibers (Okamoto, 2000). The first microfibers were invented in the mid sixties by Dr. Miyoshi Okamoto, a chemist in the Toray industries textile research laboratory. In the beginning, the single fine man-made fibers found scarcely any appropriate application. The breakthrough came with the success of imitation game leather (Rupp &

The dimensions of pores between the fibers inside the yarns (micro voids) are generally affected by fiber fineness, yarn count, yarn twist and crimp and also the deformation and

In an earlier study (Varshney et al., 2010), the effect of filament fineness on air permeability of polyester and polyester/viscose woven fabrics was observed. It was seen that decreasing filament fineness has a decreasing effect on air permeability. An another study, (Laourine & Cherif, 2011) was performed on the effect of filament fineness and weave type on air permeability of polyester woven fabrics for surgical protective textiles. The study showed that air permeability can be reduced by decreasing the filament fineness. Also, for woven fabrics with nearly same degree of cover factor, lower levels of air permeability can be reached with plain weaves than those of twill weaves. Kaynak & Babaarslan (2011), investigated the filament fineness on polyester woven fabrics for plain weave. As a result of this study, lower air permeability values were obtained by decreasing the filament fineness. The present study investigates the effects of filament fineness, weft sett and weave type on air permeability of polyester microfilament woven fabrics in a more detailed manner, aiming to determine the proper construction parameters of fabric. In addition regression

Potentially, any man-made fiber could be made into a microfiber (Smith, n.d.). Microfibers are most commonly found in polyester and nylon (Smith, n.d.; Purane & Panigrahi, 2007; Anonymous, 2000). Trevira Finesse, Fortrel Microspun, DuPont Micromattique and Shingosen are all trade names for various polyester microfibers, whereas Supplex Microfibre, Tactel Micro and Silky Touch are some of the trade names for nylon microfibers (Mukhopadhyay & Ramakrishnan, 2008). Nylon is claimed to have advantages over polyester in having a better cover, plus lower density, higher strength and abrasion resistance. Polyester is easier to spin and is available in finer filaments than nylon. Polyester raised fabrics are easier to produce. This has given polyester an economic advantage in apparel and sportswear markets (Anonymous, 2000). However, micro-denier versions of rayon, acrylic and polypropylene products are available to consumers (Purane & Panigrahi, 2007; Smith, 2011; Anonymous, 2000). Microfibers can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, viscose and silk (Smith, n.d.; Anonymous, 2000). This enhances the appearance, hand, drape

Ultra-fine fibers were produced in the late 1950s which were not of continuous filament type but were fine staple fibers of random length and found no application except for being processed into nonwoven sheets immediately after spinning. In 1961 a petal-shaped ultra fine filament type fiber described in a patent was probably the first example of a potential ultra-fine filament. Another patent issued simultaneously described splitting two component conjugate fibers of non-circular cross section into the two separate components after weaving. No attention was paid at that time for combining these technologies to produce ultra-fine fibers (Okamoto, 2000). The first microfibers were invented in the mid sixties by Dr. Miyoshi Okamoto, a chemist in the Toray industries textile research laboratory. In the beginning, the single fine man-made fibers found scarcely any appropriate application. The breakthrough came with the success of imitation game leather (Rupp &

analyses were conducted to estimate the air permeability before production.

flattening of the yarns (Çay & Tarakçoğlu, 2008).

**2. General properties of microfibers** 

and performance properties of the fabrics (Basu, 2001).

Yonenaga, 2000). This was the first attempt to produce an ultra fine fiber intentionally. Matsui et al. of Kanebo also tried multi layer conjugate spinning in 1968 for the production of ultra fine filaments. Since no application of ultra-fine fibers was foreseen in the 1960s, there had been no technical or commercial interest in them until Toray put the new suedelike material on the market in 1970 (Okamoto, 2000).

Microfibers are being increasingly used throughout the world for various end uses due to their fineness, high performance characteristics and their unique ability to be engineered for a specific requirement (Anonymous, 2000). Fundamental characteristics of microfibers are as follows;


One caution related to synthetic microfibers is heat sensitivity. Because the fiber strands are so fine, heat penetrates more quickly than thicker conventional fibers. So, microfiber fabrics are vulnerable to damage from careless ironing. They will scorch or glaze if too much heat is applied for a too long period (Smith, n.d.; East, 2005).

They also have a tendency to snag easily and, as with all fine fabrics, they need to be handled with care. Jewelry cause pulls, snags or general abrasion to garments (Smith, n.d.; East, 2005).

Since microfibers have an increased surface area, resulting in a dyeing rate four times higher than that of normal which can cause unlevelness in dyeing. They require more dyestuff than

polyethylene and polyphenylene sulfide are the polymers employed as island components (Okamoto, 2000). The various combinations of polymers to form fibers by this method successfully are polystyrene/polyamide and polystyrene/polyester (Purane & Panigrahi, 2007). The sea component is removed by dissolving it in a solvent after conventional processing into woven, knitted or nonwoven fabrics. This technology provided a means of industrial production of suede type artificial leather, silk like fabrics, wiping cloths and fine filters. Since the ultra fine filaments (the island component) are sheathed by the sea component, they are protected from damage during later processing (Okamoto, 2000).

Three component spinning can be carried out with two island components by designing a three component spinneret assembly. The sea component can be reduced to 2-10% of the total components, but the space between the ultra fine filaments is also reduced and this may lead to poorer handle of the products. When the sea component is small in amount and not miscible with the island component, the splitting can be carried our mechanically

This type of spinning aims to utilize the second component in the final product by splitting the two components instead of removing the second component by dissolving. The ultra fine fiberization is performed by a mechanical or chemical process in the splitting and separation types of spinning (Okamoto, 2000). This method of microfiber production involves extruding a bicomponent fiber which two polymers with poor adhesion to each other are used (Richards, 2005). Applications of these fibers are suede for clothing and upholstery, silk like fabrics, wiping cloths, wall coverings, automobile trims, golf gloves and moisture-permeable and water-repellent fabrics (Okamoto, 2000; Richards, 2005). In this method the overall shape of the fiber determines the ease of splitting. If the components are in a radial configuration then splitting is more difficult than if one polymer is located at the ends of the lobes in a multilobal shape (Richards, 2005). Suitable polymer combinations for splittable bi-component filament spinning are polyamide/polyester and

Two components are spun into a conjugate fiber of multilayered structure with an ovalshaped cross section, which is microfiberized into filaments of 0.2-0.3 denier (Okamoto,

Ultra fine fiber of the staple type is produced by the methods including:

(Okamoto, 2000).

**3.1.2.3 Multi-layer type** 

2000).

**3.1.2.2 Separation or splitting type** 

polyester/polyolefin (Purane & Panigrahi, 2007).

**3.2 Production of staple type microfibers** 

1. Melt blowing or jet spinning

3. Polymer-blend spinning 4. Centrifugal spinning

6. Turbulent flow-moulding 7. Bursting (Okamoto, 2000).

2. Flash spinning

5. Fibrillation

normal fibers to attain a given shade depth (Jerg & Baumann, 1990; Anonymous, 2000; Falkai, 1991).
