Question 42 (Textile Engineering & Fibre Science)
Match the items in Group I with those in Group II.
|Group I||Group II|
|P||Crabbing||1||Cut and remove projecting fibres|
|Q||Decatising||2||Moisture, heat, mechanical action|
|R||Milling||3||Perforated drum with saturated steam|
|S||Cropping||4||Winding, treatment with hot water|
|(A)||P-4, Q-3, R-2, S-1|
|(B)||P-3, Q-4, R-2, S-1|
|(C)||P-2, Q-3, R-4, S-1|
|(D)||P-4, Q-3, R-1, S-2|
Frequently Asked Questions | FAQs
What is the process of crabbing?
Crabbing is a textile finishing process that involves treating the fabric with a crabbing solution to improve its dimensional stability and appearance. The process is commonly used for silk and wool fabrics that have a tendency to shrink or distort when exposed to water or humidity.
The crabbing process typically involves the following steps:
Preparation: The fabric is first washed and scoured to remove any impurities, such as dirt, grease, or sizing. This step is important to ensure the uniform penetration and absorption of the crabbing solution.
Crabbing solution preparation: The crabbing solution is prepared by dissolving a mixture of potassium or sodium bichromate and sulfuric acid in water. The solution is heated to a specific temperature and concentration, depending on the type and thickness of the fabric.
Immersion: The fabric is then immersed in the crabbing solution for a specific time, typically ranging from a few minutes to several hours. The immersion time depends on the desired degree of dimensional stability and the type of fabric.
Neutralization: After the immersion, the fabric is removed from the crabbing solution and rinsed thoroughly with water to remove any excess chemicals. The fabric is then treated with a neutralizing solution, such as sodium carbonate, to neutralize the acidic residues and prevent further chemical reactions.
Drying: The fabric is then dried under tension to prevent shrinkage or distortion. The drying can be done by various methods, such as air-drying, machine-drying, or steam-drying.
The crabbing process can improve the fabric’s resistance to water, moisture, and wrinkling, as well as its luster, hand, and drape. However, the process can also have some environmental and health concerns, as the crabbing solution contains hazardous chemicals and produces toxic fumes and wastes. Therefore, the process should be carried out in a well-ventilated and controlled environment, and the waste products should be disposed of properly.
What is the purpose of Decatising machine?
A Decatising machine is a textile processing machine used to remove excess fiber or hairiness from woolen or worsted fabrics, which have undergone the process of weaving or knitting. The primary purpose of decatising is to give the fabric a smooth and uniform surface. The machine achieves this by subjecting the fabric to a combination of heat, moisture, and pressure, which causes the fibers to shrink and compress, resulting in a smoother finish.
In addition to improving the appearance of the fabric, decatising also has functional benefits such as improving the fabric’s dimensional stability, reducing shrinkage, and improving its ability to resist creasing. Decatising is an important step in the finishing process of woolen and worsted fabrics used in high-end garments, suits, and other apparel.
What is the process of milling?
Milling is a textile finishing process that involves subjecting the fabric to mechanical and chemical treatments to improve its appearance and properties. The process can be used on a variety of fabrics, including wool, cotton, and synthetic fibers.
The process of milling typically involves the following steps:
Scouring: The fabric is washed to remove any dirt, oil, or other impurities that may be present.
Fulling: The fabric is subjected to mechanical action, such as pounding or rolling, to improve its texture and hand. Fulling can also cause the fibers to interlock, which improves the fabric’s strength and durability.
Crabbing: The fabric is stretched and dried under tension to improve its dimensional stability and reduce shrinkage.
Raising: The fabric is brushed with wire brushes to create a fuzzy or napped surface, which improves its warmth and softness.
Shearing: The excess fibers on the raised surface are trimmed or sheared off to create a smooth finish.
Pressing: The fabric is pressed to remove any wrinkles or creases that may have formed during the milling process.
The specific process and techniques used in milling can vary depending on the type of fabric being processed and the desired end result.
What is the objective of shearing?
The objective of shearing in textile finishing is to create a smooth and uniform surface on a fabric. During the textile manufacturing process, fabrics often develop a fuzzy or uneven surface due to the natural properties of the fibers or the processing techniques used. Shearing is a finishing process that involves trimming or cutting off the excess fibers to create a smooth surface with a consistent pile height.
Shearing is commonly used in the production of carpets, rugs, and upholstery fabrics to create a uniform surface that is easier to maintain and clean. Shearing can also be used on other types of fabrics, such as woolen or worsted fabrics, to create a smoother finish that is more aesthetically pleasing and easier to work with in garment construction.
The degree of shearing required depends on the type of fabric and the desired end result. A heavy shearing can create a short pile, while a lighter shearing can create a longer pile. The process is often carried out using specialized shearing machines that can be adjusted to achieve the desired level of shearing.