Techniques of Warp Yarn Sizing in Weaving Preparatory Process
Department of Textile Engineering
Daffodil International University
What is Sizing?
Sizing is a generic term for applying various compounds to warp yarn to bind the fiber together and stiffen the yarn to provide abrasion resistance during weaving. It is the process of applying protective adhesive coating on the yarn surface. The main objective of sizing is to form a uniform layer of protective coating over warp yarn and lay down protruding fibers that project out of its surface. Sizing is the most important segment of weaving preparatory process. The old adage that sizing is the heart of weaving still holds good today. This statement is all the more important in today’s environment when loom speeds have increased tenfold from those used in shuttle looms. The weaving process depends upon a complexity of factors which include the material characteristics, the sizing ingredients, the sizing operation, and the yarn parameters.
In fabric manufacturing process, the warp yarn is subjected to substantial abrasive forces during weaving. Thus, the yarn has to be reinforced with a polymer coating, the so-called size. Due to the high number of cycles of a weaving loom (up to 700 turns/min), the productivity of such a unit is high. As a result, with increasing speed the costs of a single-warp yarn breakage rise. A high number of yarn breakages will lower the product quality; however, it will also lead to a dramatic reduction in productivity of such a loom. Thus, the appropriate sizing and climate control in the weaving floor are of high economic significance.
Techniques of Warp Yarn Sizing:
The function of a sizing machine is to put a size on to the warp in the most suited manner to the particular type of fiber used, and to the ultimate fabric construction which enables the weaving operation to be performed without difficulty at a high rate of efficiency.
Sizing machine can be classified according to the method of drying as follows:
Techniques of warp yarn sizing can be classified on the basis of method of application into conventional wet sizing, solvent sizing, cold sizing and hot melt sizing. The main parts of conventional sizing machine include (Figure-1) creel, sizing box, drying section, leasing section, head stock and size cooker.
Wet Sizing: In conventional wet sizing, the fundamental constituents of size recipe are the size materials and a solvent usually water. The sizing materials are broadly classified into three groups namely adhesives, softeners and auxiliaries
Solvent Sizing: Sizing is accomplished by using a non-aqueous organic solvent as the treatment media instead of water. Chlorinated hydrogen is mostly used as solvent and 1/10 th of energy is required to evaporate solvent.
Hot melt Sizing: Suitable for high speed weaving e.g. shuttle fewer looms where there is risk of yarn hairiness. Sizing is done in the warping machine by having a special arrangement called size applicator. The size is kept in cake form where the warp is kept pressed.
Foam Sizing: Here the solvent is replaced by water. Foam of size is used which must possess liquor, a gas, mechanical energy and thermal energy. Thus 70% energy is saved and production is increased.
Blend Sizing: Manmade fibers are more sensitive to heat and tension. However successful size will result better performance than 100% cotton. In order to perform well blend sizing needs both machinery as well as operational requirements.
Non-Conventional Aqueous Sizing:
Double Cylinder Sizing: This consists of only two drying cylinder or two sow box arrangement which leads to more energy consumption.
Multi Cylinder Sizing: This consists of more than one sow box and several groups of drying cylinders. This is suitable for densely spaced yarns. Warp yarns are dried separately by separate drying arrangement. This is also suitable for dyeing and sizing together resulting in saving of wastes.
Draw-sizing: A system linking draw warping and sizing in a continuous process. A typical system includes the elements like creel, eyelet board, warpdraw machine, intermingler, tension compensator and break monitor, sizing bath, dryers, waxing and winding units.
Non-Conventional Dry Sizing:
The method of “dry” sizing has long been known, but has not received widespread industrial application due to the high cost of the sizing ingredients. This is carried out by spraying dry size powder on the warp sheet and the size powder is thought to be fixed in the warp yarn due to electrostatic force of attraction. This process ensures the reduction of cost of raw material and reduction of pollution.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.