Introduction to Sizing
Sizing is the process of impregnating
the warp with size solution
Until the development and use of
man-made commodities, measuring materials used in the textile industry had to
meet the needs of the natural fiber weaving industry. The most common sizes in
the cotton industry use natural starch. Natural starch, such as corn, wheat,
tapioca, and the like, has a tendency to form very strong films. To overcome
the hardness of natural starch, weaving is done at very high humidity.
Nevertheless, natural starch does a useful job, and it still works in the
cotton industry. Because starch has a chemical structure similar to that of
cotton, starch adheres well to cotton and rayon. The first man-made fiber with
the same chemical price as cotton.
Starching can be done by
enzymatic treatment and making the damaged product insoluble. Starchy materials
are relatively inexpensive and are still widely used in the textile industry.
Starch needs to be cooked and placed at an even higher temperature, which
causes some rayon processing problems. By the size of the rayon type gelatin
the natural material of proteins derived from the skins and skins of animals
was developed. This content can be used at lower temperatures than those used
for natural starch. This material has been shown to be sufficient in rayon size
without causing any ‘‘ hot ’damage. Protein digestion protein is used to obtain
information. This trend continued until the 1940's when the first production
threads appeared. In 1938 nylon fiber, which is thermoplastic in nature,
emerged on the scene, requiring the manufacture of a measuring device that can
be used at low temperatures and also adheres to the hydrophobic surface of the
fibers. New types of measurements included chemicals such as carboxymethyl
cellulose (CMC), polyvinyl alcohol (PVA), copolymers acrylic acid, and other
water-soluble substances that did not require cooking before use. The chemistry
of these materials makes thinking easier and simpler. By controlling the
polymerization rate of these compounds, sizes with extremely diverse body
structures and solvents are made. Some of these sizes are also combined with
starch to estimate the cost of the measurement while simultaneously developing
the repair properties of the fibers during weaving. Another category of
building materials called '' binders '' is also designed to improve adhesion to
synthetic film-based structures. The chemical materials available on the market
allow textile specialists to make measuring ingredients to meet the processing
needs of various types of fibers and speed weaving. In this chapter, the
chemical nature and various chemical and physical components of the measurement
ingredients will be discussed.
Objectives of sizing
- To increase the strength
of the yarn by 10-20 %
- To reduce the hairiness
of yarn
- To increase the abrasion resistance
of the yarn against other yarns and various weaving m/c elements.
- To reduce the fluff and fly
- The ultimate goal of sizing is to reduce warp breakages during weaving
Size material on a yarn
Different Sizing terms
- Size concentration
- Mass of oven dry solid matter
in size paste
- Size take-up / Size pick-up
- Mass of paste taken up in the
size box per unit weight of oven dry unsized yarn
- Size
pick-
- Size add-on/ Size percentage
- Measure of dry weight of size
material in warp yarn
𝑆𝑖𝑧𝑒 𝐴𝑑𝑑−𝑜𝑛 = (𝑤𝑡. 𝑜𝑓 𝑠𝑖𝑧𝑒𝑑 𝑦𝑎𝑟𝑛 −𝑤𝑡. 𝑜𝑓 𝑢𝑛𝑠𝑖𝑧𝑒𝑑 𝑦𝑎𝑟𝑛)/(𝑤𝑡. 𝑜𝑓 𝑢𝑛𝑠𝑖𝑧𝑒𝑑 𝑦𝑎𝑟𝑛) × 100%
Sizing-Weaving Curve
A typical sizing–weaving curve is as shown in the figure. Initially the warp breaks decrease with the increase in size add-on level. This is due to the associated increase in yarn strength and reduction in yarn hairiness. The coating of the protective size film around the yarn provides improved resistance to abrasion and also affords adequate protection to the weak places in the yarn. The reduction in warp breakage rate with an increase in size add-on reaches a point beyond which further size add-on will not show any significant improvement in yarn performance on the loom. The weaving efficiency, which is inversely proportional to warp yarn end breakage rate, reaches its peak when the warp breakage rate is at its minimum. The optimal range of size add-on is usually between points A and B as shown in the typical curve. Increasing the size add-on beyond the optimum, in fact, has a detrimental effect on weaving performance since the warp breaks increase. Excessive size add-on leads to an increased penetration of the size, which makes the yarn inflexible. Also, higher size add-on may tend to coat the yarn with a very thick film of size which is not sufficiently anchored to the fibers. Such a thick coating of size film may have a lower extensibility compared to the extensibility of the warp yarn itself. Inflexibility of the yarn and a size film not bound securely have a net effect of size film shedding due to its easy rupturing, thus making the yarn vulnerable to intensive abrasion action and leading to a higher warp breakage rate. The best weaving efficiency region consistent with optimal size add-on is usually achieved in practice by trial and error. In the next chapter the different methods used for correlating laboratory evaluation and its relationship to actual weaving performance are discussed.
Size Ingredients
Adhesive substances
- To consolidate fibers, give smoothness, body and stability to yarn
- To bind the fibers & to increase the strength
- To cover the yarn surface.
- Unevenness of yarn (thick, thin and neps)
- To lay down the protruding fibres
Properties of adhesives
- · Good adhesion
- · Good solubility
- · Better penetration
- · Good elasticity
- · Improved wetting properties
- · Good drying
- · Anti mild growth
- · Viscosity
- · Film strength
Natural Adhesives
· These are Carbohydrates
Plant Adhesives
· From the seeds of different plants, e.g., maize, potato, wheat, rice, sago (starch), tapioca (starchy grains), banana, guar gum etc.
Animal Adhesives
· From the bones & skin of animals & from fish. It is known as glue.
Starch
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. Large quantities are also used by the paper and food processing industries, for medicinal and adhesive applications, in the fermentation of alcoholic beverages, and even as explosives. It is one of the most abundant agricultural ‘‘renewable’’ resources found in nature. Starch occurs widely in plants but is found in its purest form in the seeds (such as in wheat, corn, rice, and sorghum), in the roots and tubers (such as in potato, tapioca, and arrowroot), or in the stem pith of plants (such as in sago).
Disadvantages Of Natural Adhesives
- Difficult to make paste
- · Deterioration of paste
- · Attacked by micro organisms
- · Change in viscosity
- · Difficult to desize
· Reacting with natural adhesives produces derivatives.
Modified Starch
· Carboxymethylcellulose. (C.M.C)
· commercial grades are 5050,5075 & amisol
Synthetic Adhesives
· Simple & synthesize polymers,
· Used for natural & Synthetic yarns.
- P.V.A (2017, 217)
- Acrylic polymers
· To prevent adhesive & weighting substances to become hard or powdered,
·To preserve soft & supple qualities of yarn
Lubricants & Softeners
· To make the yarn soft & pliable (flexible).
· To make the yarn surface smooth & uniform.
· To increase the penetration of size liquor in to yarn.
· To increase the moisture absorption in the yarn.
· It is used 5~10% on the basis of adhesives
· Glaserides produced by chemical reaction of glascerine with steric acid.
· Most commonly used softeners are mutton tallow, Sico D-52, Olinor, Polytex.
Antiseptic substances
· To prevent the development of mildew is called Antiseptics substances. Protect the warp from bacteria & mild growth.
· It is used 0.3~0.5 % of starch.
· Copper sulphate (CuSO4) & Zinc chloride (ZnCl2).
Moistening substances
· To keep yarn in humid condition is called moistening substances.
Weighting substances
· To increase weight of cloth is called weighting substances.
· Used for finer counts (silk) to increase the weight of yarn.
· China clay, Chalk powder, MgSO4 etc
Properties of good size material
A good size should have follow properties· Easy to desize in processing.
· Cost should minimum. Cost of sizing is approximately 10~15% cost of weaving.
· Size used has ability to absorb moisture.
· After applying size appearance of material should good.
· Size should have property to resist bacteria and mildew.
· Size should have property to dry easily
Choosing the proper chemistry for sizing
Several factors are considered while choosing size mix as simple as possible.· Yarn material(cotton,PC,rayon,wool)
· Yarn hairiness
· Yarn structure( OE,carded)
· Yarn twist
· Water to be used for cooking
· Type and speed of weaving machine ( rapier, projectile)
· Desizing procedure
· The penetration of size in yarn also depends on yarn twist for ring spun yarn
· High twist yarn require less viscous solution.
- · Pour water in the kettle.
- · Add PVA and stir it for 10min.
- · Add starch and keep stirring.
- · Provide steam for 30 min at 950C.
- · Add Accra base and steam it for 3 min.
- · Stop steaming and add Petra soft.
- · Then it is transferred in storage tank and is ready to use.
Sizing Machine
Zones of Sizing machine
- Creels—unwinding zone
- Size boxes—sizing zone
- Drying cylinders—drying zone
- lease rods—splitting zone
- Head stock—winding zone
Creel
· Capable of carrying heavy warper’s beams
· Smooth and steady unwinding without
· Side to side swinging
· Entanglement of two warp sheets
· Ends must not touch the flanges of warper beam
· Warping Beam Braking Systems
· preventing the over-running of the beams (during breakage of yarn)
· control of yarn tension between the size box and the creel (during normal speed)
· The size box is the most important section of the sizing machine.
· During the slashing process, the sheet of yarns is passed through the size box which contains the hot water solution or mixtures of sizing agents.
· The yams pick up the required quantity of size solution in the size box, any excess size is squeezed off as the yams pass through squeeze rolls.
· The size box is the most important section of the sizing machine.
· During the slashing process, the sheet of yarns is passed through the size box which contains the hot water solution or mixtures of sizing agents.
Cylinder Drying
- · The size box is the most important section of the sizing machine.
- · During the slashing process, the sheet of yarns is passed through the size box which contains the hot water solution or mixtures of sizing agents.
- · The yams pick up the required quantity of size solution in the size box, any excess size is squeezed off as the yams pass through squeeze rolls.
1. Coated
with non-stick coating, e.g. Teflon
·
preventing the size and yarns from sticking
while the warp is partially dried
2. Cylinders
arrangement can be
- · Horizontal
- · Vertical
- · Both
3. Number
of drying cylinders depends upon
- · Density of warp
- ·
Sizing speed
· Temperature range from 1300-1450C
Drying zone Advancements
1. Convection
Drying
- · hot air is used as a drying medium
- · Uniform drying
2. Infrared
and Microwave Drying
- · conserve energy
- · Efficient
- · cost-effective
Lease Rods
·
Lease
rods separate the warp yarn sheets, which are stuck together because of
the drying of the size film
- · A series of lease or bust rods, with one large diameter busting rod
- · Chromium-plated hollow cylindrical bars flattened at both ends
- ·
No.
of leasing rods=no. of warp beams -1
Head Stock
- · Winding or take-up unit supporting the weaver’s beam and necessary drive gears
- · Imparts necessary beaming tension for compact and straight winding
- · A positively driven roll, commonly known as the delivery roll or draw roll
- · Cork (stopper) and rubber covered placed between two heavy chrome-plated nip rolls
- · Delivery roll moves at a constant speed
- · Speed of the weaver’s beam is adjusted to impart the necessary winding tension
- · Driving the weaver’s beam at a constant tension
- · surface speed of the beam keeps increasing as the diameter of the beam increases
- consequently the winding
tension also increases
- Reduction in rpm
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