Techniques of Warp Sizing
Department of Textile Engineering
Daffodil International University
Introduction of Sizing:
Sizing is the process of applying protective adhesive coating on the yarn surface. This 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.
Techniques of Warp Yarn Sizing:
Sizing machine can be classified according to the method of drying as follows:
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.
|Fig - 1: Conventional Sizing Machine|
Dry Sizing: 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.
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.
|Fig - 2: Non-Conventional Sizing Machine|