Definition of Sizing | Objects of Sizing | Sizing ingredients function | Description about Size take up percentage and Sizing faults

Sizing

The process of applying an adhesive coating on the warp yarn to minimize yarn breakage during weaving. The most commonly used sizing machine is slasher sizing machine. SIM fabric used combined hot air and cylinder type sizing machine.

Fig: Sizing Process.

Objects of sizing m/c

1.   To increase the smoothness of the warp yarn

2.   To reduce hairiness of warp yarn

3.   To increase the strength of warp yarn

4.   To improve the weave ability of warp yarn

5.   To increase the elasticity

6.   To remove the projecting fibers

7.   To increase the tensile or breaking strength for cellulose yarn.

Sizing ingredients function

Starch:

Starch is the main sizing ingredients. They coat the warp yarn with a film & impart smoothness by binding the projecting fibers to the yarn surface. The viscosity of the size solution is controlled by the amount of starch, the recipe, degree of mechanical mixing, temperature & time of boiling. E.g. Potato, CMS (Carboxyl Methylated Starch), PVA (Polyvinyl Alcohol)

Binder:

These materials penetrate into the yarn & contribute in increasing yarn strength. These materials can be used as an independent gum & substitute of starch products. E.g. Polyacrylamide, Polyacrylonitrile etc.

Softener:

The hard fragile film is softened by addition of softener. They increase flexibility of yarn after sizing.  E.g. Tallow, Soap, Japanese wax, Modified wax, Artificial wax.

Anti-septic agent:

The size recipe consist starch which the protein substances in the favorable medium for the development of the micro-organism (Fungi, Mould etc.). The sized warp or grey cloth is stored for long time; the anti-septic agent is used to prevent the growth of micro-organism in the grey cloth.

Weighting agent:

These agents are used to increase the weight of the fabric. The fabrics are to be sold at grey stage or require the special type of finishing to get fuller appearance are sized with the weighting agent.

Factors Affecting the Size Take Up Percentage

q  Viscosity of the size recipe: If viscosity of the size liquor is not proper, it is difficult to penetrate for the size material to the core of the yarn.

q  Lubrication: Lubricant can exist at the surface or exist inside the structure and later work itself to the surface as the yarn rubs over a friction surface.

q  Degree of size penetration: It determines the stiffness for a given yarn bearing a given size. So if Degree of penetration is not proper, size take up% will be un-uniform.

q  Squeeze roller pressure: If the pressure of squeeze roller is not sufficient, size add-on may be increased or decreased.

q  M/C Speed: If m/c speed is high or low consequently size take-up% may be less or high correspondingly than the required take-up%.

Different sizing faults & state the causes of these faults

q  Size spot:  Size material should be added gradually to the mixing tank for good mixing. If it is added at once, spot are appeared on the yarn.

q  Repeating warp streaks: This defect is due to uneven tension in the prebeam.

q  Shinnery: This defect due to the friction between the yarn & drying cylinder.

q  Sandy warp: Due to not crushed or grind the size material properly.

q  Ridge Beam: This fault occurs due to uneven distribution of yarn in wraith.

q  Hard sizing: If the size material are applied too much, the size becomes hard which causes hard sizing.

q  Sizing dropping: This defect due to not optimum the viscosity of the size solution.

q  Size stitching: Due to improper drying after sizing.

q  Uneven sizing:

1.   Due to over or under sizing.

2.   Due to over or under concentration of size liquor.

                   Posted By-

                Amanuzzaman

         Campus Correspondent,

Shyamoli Textile Engineering College.