**5. Weaving of microfibers**

Microfilaments demand extraordinarily high quality weaving warps (Rupp & Yonenaga, 2000). In the case of warping microfiber yarns versus warping conventional fiber yarns, it must be considered that the smaller amount of force is needed to break a microfiber filament during warping. In addition, the eyelets used in the tension device in the creel of warping machine must be made of a low friction material. The surfaces must be free of cuts and snags. Also, the reed blades must be absolutely free of any snags or bars (Basu, 2001).

Due to their fineness the total surface area of microfiber yarn is far greater than ordinary fibers (Anonymous, 2000). The surface of microfiber yarns is 10-15% larger than conventional fiber yarns. Due to the higher surface area of microfiber smoothed yarn absorbs approximately 10% more sizing agent and textured yarns approximately 15% more sizing agent than conventional yarn. By reducing the viscosity of the sizing agent distribution of the sizing agent may be improved. The squeezing pressure must be adapted to the speed to achieve regular sizing. As a result of the larger surface and the small mass of the individual filaments the microfiber can be heated faster as drying also occurs faster. So cooling must be effected in a few seconds. The drying temperature can be lowered by 10% in the case of microfilaments (Basu, 2001). Since microfibers have very small interstices, desizing become quite difficult and costly. Desizing must always be clean to prevent problems in dyeing. Knowledge of the type of size used is very important to optimize the desizing process. Pretreatment must be done either on tensionless open width washers or in the overflow or jet dyeing machine. Control of PH is important for optimum size removal (Anonymous, 2000; Rupp & Yonenaga, 2000).

Many machine manufacturers recommend the use of air jet and rapier looms for microfilament woven fabric production. They also recommend the use of prewinding units and yarn brakes, which are suitable for processing filament yarns for weft insertion.

essentially round. But after the texturizing process the view of the filament cross section was

**Yarn tenacity, cN/Tex** 3.0 3.6 3.6 3.0 3.0 **Yarn breaking elongation, %** 21 27 25 24 26 **Shrinkage , %** 3.0 2.6 3.6 4.0 4.5 **Crimp contraction, %** 15 11 8 8 5 **Crimp module, %** 10 6 4 4 3 **Crimp stability, %** 81 82 79 77 72 **Oil content, %** 3 3 3 3 3 **Intermingling frequency, points/meter** 90 100 90 70 60

**(Stability at 3% elongation)** 45 50 50 45 60

**Yarn linear density, dtex** 110

Fig. 1. Microscopic views of weft yarn cross sections by magnification X200

Determination of number of threads per unit length

Structural properties of sample fabrics after thermal fixation and desizing processes were determined according to following standards and results were given in Tables 2, 3 and 4.

0.57 dtex 0.33 dtex

3.05 dtex 1.14 dtex 0.76 dtex

ISO 7211-2 Textiles -- Woven fabrics -- Construction -- Methods of analysis -- Part 2:

ISO 3801 Textiles -- Woven fabrics -- Determination of mass per unit length and mass

ISO 5084 Textiles -- Determination of thickness of textiles and textile products

**Weft yarn filament fineness, dtex 3.05 1.14 0.76 0.57 0.33** 

changed to cornered shape.

**Intermingling retention** 

per unit area

Table 1. Weft yarn properties used in the study

Basically weft yarns must be inserted with the greatest care. In this respect, processing should be effected with at least two yarn storage units in order to keep taking off speed as low as possible. Warp ends should be fed by a finely controlled warp let off system with an absolute tension sensor and a positively controlled rotating back rest roller. Abrasion resistant materials must be employed to prevent filament breakage in the case of the winding unit. For this the use of vulcanized or rubberized materials are suggested. For double width weaving machines, an additional pressure roller should be used for fabric slippage. Textured filament yarns should be more intensively intermingled in order to ensure good running characteristics. This may however have a rather detrimental effect on air consumption in the case of air jet looms (Rupp & Yonenaga, 2000). The harness with drop wires of warp stop motion, the reed and the healds come into particularly intimate contact with microfiber yarns. The surfaces of these items, therefore, need to have particularly low roughness. Fabrics woven with microfiber yarns are often densely constructed; beat up must also be relatively severe. If the reed wires have sharp edges, they can easily cut the individual filaments and thus damage the yarn. Weft accumulators must provide sensitive gentle tensioning of fine yarns. Two or more weft accumulators must be used with weaving machines to reduce the withdrawal of weft insertion. Temples recommended for silk and silk like fabrics must be used for microfiber yarn fabrics in order to prevent the fabric bowing out in the selvedge zone (Basu, 2001).
