Sizing Ingredients in Textiles:
We know that sizing is the heart of weaving. Sizing improves the weavability of warp threads by reducing thread–thread and thread–metal friction. The weaving process depends upon various factors which include material characteristics, sizing ingredients, sizing operation and yarn parameters. Each type of textile material has its own merits and demerits and the type of size ingredients have to be used accordingly to compensate for their demerits. The size material used in sizing consists of a number of ingredients mixed together in suitable proportions to form a viscous paste. Each size ingredient should impart a particular property to the yarn. The type of sizing ingredients differs for different types of textile materials.
Properties of Sizing Ingredients:
There are a number of desirable properties of sizing ingredients. A good sizing ingredient should have most if not all of these properties; however, sizes that are deficient in some of these properties still may be used.
Properties of a good sizing ingredient:
- Environmentally safe (nonpolluting)
- Good film former
- Reasonable use economics
- Penetration of yarn bundle
- Elasticity
- Good film flexibility
- Good specific adhesion
- Good frictional properties (lubricity)
- Transparency
- Bacterial resistance (mildew)
- Reasonable strength
- Controllable viscosity (fluidity)
- Water soluble or water dispersible
- Good hygroscopicity characteristics
- Uniformity
- Clean split at bust rods
- Improves weaving efficiencies
- No effect on drying
- Reasonable extensibility
- Recoverable and reusable (or treatable)
- Low static propensity
- No skimming tendency
- Easily removed (desized)
- Easily prepared
- Lack of odor
- No beam blocking
- Compatible with other ingredients
- Good abrasion resistance
- Neutral pH
- High fold endurance
- Insensitive to high heat (overdrying)
- Low BOD
- No build-up on dry cans
- Reduced shedding
- Rapid drying
- No redeposition of size
- Insensitive to changes in relative humidity
Different Types of Sizing Ingredients:
There are two types of sizing ingredients, namely the primary and secondary ingredients. The primary ingredients are those that are essentially required in the size paste whereas the secondary ingredients are those that may or may not be added to the size mixture according to the requirements. The primary ingredient is the main ingredient and it helps to give additional strength to the yarn and also improves its abrasion resistance. The other ingredients known as the secondary ingredients give additional properties to the yarn such as feel, weight, appearance etc.
The sizing ingredients are also categorized into two types based on their solubility which is most important for a processor that are as follows:
a) Water insoluble sizes: Starch (potato, maize, wheat, rice, etc.) and modified starches.
b) Water-soluble sizes: CMC, PVA, Polyacrylates, Polyester, etc. Watersoluble sizes (PAC, PVA, CMC, polyester) first swell in water and are then removed with the help of surfactants and dispersing agents at high temperature and turbulence.
Sizing Ingredients and Their Functions:
A. Starch:
Natural starch and its derivatives still constitute nearly 75% of the sizing agents used in the textile industry throughout the world. Starch is a useful sizing ingredient even though it has a high biological oxygen demand (BOD), lacks bacterial resistance, and is sensitive to overdrying; cannot be recovered; and must be cooked to achieve uniform properties besides other disadvantages. Starch was at one time the primary sizing agent for textiles, and it is still used extensively either alone or in blends with other sizing agents. Yet it is a useful size material primarily because it is inexpensive, is easily desized, is a renewable resource, has good adhesion to cellulosic fibers, and can be modified and/or derivatized to yield a wide range of size film properties. In other words the usefulness of a size material for a specific application will depend upon the nature of the fibers of yarns being sized (e.g., cellulosic, nylon, polyester, etc.), the type of yarn (ring-spun, open-end, air-jet), the type of weaving machine being employed (shuttle, air-jet, rapier, projectile, etc.), and the characteristics of the fabric being woven (style, construction, weave, twist, yarn count, etc.).
Functions:
- Improves yarn strength
- Reduces yarn friction
- Enhances yarn handling
- Improves fabric appearance
- Prevents yarn breakage
- Protects fiber surface
- Facilitates dyeing and finishing
- Regulates moisture absorption
B. Gums:
These materials from the base of size. There are two types of gum:
- Natural: Until lately, mainly edible products were used as gums – starches used as 75% of size ingredients and it will continue till to near future. Common starches are potato, maize etc. Wheat flour, corn flour.
- Synthetic: Polyvinyl alcohol, Carboximethyl cellulose, Polyacryloamide.
Functions:
- Coat the warp yarn with a film.
- Impart smoothness.
- Blind the protruding fibers to the yarn surface.
- Increase elasticity.
C. Lubricants or Softeners:
Vegetable and animal fats, Japan wax, tallow, cotton seed and castor oils, stearine, glycerin, soap, TRO etc.
Function:
- To give a softer feel to the sized yarn.
- To reduce stickiness of yarn.
- To smoothen the yarn.
D. Antiseptic or Anti Mildew Agent:
Phenol, boric acid, carboxylic acid, zinc chloride, sodium silicofluoride, cresol etc. The quantity used is very low 0.1 to 2%.
Function:
- To prevent the growth of mildew.
- To prevent spoiling of the size mix during storing it for long time.
- To help to store the sized yarn.
E. Wetting Agent:
Sulphanol A, soap, avirol, alizarin oil etc. The amount of wetting agents introduced into the size should not exceed 0.1 to 0.15 gm/ltr.
Function:
- To improve the size wet ability.
- Improve the penetration of the size between the fibers.
- Uniform distribution of the sizing solution on the yarn surface is obtained.
F. Antifoaming Agent:
Silicones, stearine-paraffin emulsions, benzene, pyridine. The antifoaming agents in amounts of 0.05 to 0.1 gm/ltr are stirred in a small quantity of warm water.
Function:
- To prevent formation of foam.
G. Tinting Agent:
Blue is used as tinting agent.
Function:
- To increase the brightness and remove yellowish color of yarn.
- To prevent dusting off.
- To form a particular shade.
H. Weighting Agent:
The most commonly used substances are soluble inorganic powders such as china clay, talc, barium or calcium sulfate.
Function:
- To give additional weights to the goods.
- To prevent opening of cloth.
References:
- Textile Sizing by Bhuvenesh C. Goswami, David Hall, and Rajesh D. Anandjiwala
- Weaving Preparation Technology By Dr. N. Gokarneshan
- Pretreatment of Textile Substrates by Mathews Kolanjikombil
You may also like:
- Yarn Sizing: Important Warp Preparatory Process
- Automation in Warping and Sizing Process
- Parameters for the Process Control in Sizing of Warp Yarn
- Maintenance Process of Sizing Machine and Its Importance
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
