Sunday, December 27, 2015

Advantage & Disadvantage of Synthetic Fibers

Advantages of Synthetic Fiber : 

1. A great advantage of synthetic fibers is that they are more durable than most natural fibers. 
2. Many synthetic fibers offer consumer-friendly functions such as stretching, waterproofing and stain resistance.
3. Synthetic fibers are not a good source for these fabric-damaging insects.
4. Synthetic fibers do not break down easily when exposed to light, water, or oil.
5. Modern synthetic fabrics can look and as luxurious as silk or wool.

Disadvantages of Synthetic Fiber :

1. Synthetic fibers burn more readily than natural.
2. More electrostatic charge is generated by rubbing than with natural fibers. 
3. Prone to heat damage. Melt relatively easily.
4. Not skin friendly, so uncomfortable for long wearing.
5. Allergic to some people.
6. Non-biodegradable in comparison to natural fibers.

Viscose Rayon :

Viscose is both a semi-synthetic fabric formerly called viscose rayon or rayon and a solution of cellulose xanthate produced by treating dissolving pulp with aqueous sodium hydroxide and carbon dssulfide used to spin the viscose rayon fiber. Byproducts of the production process include sodium thiocarbonate, sodium carbonate, and sodium sulfide. Viscose rayon fiber is a soft fiber commonly used in dresses, linings, shirts, shorts, cats, jackets, and other outer wear, it is also used in industrial yarns, unholstery and carpets. It is also used in the casting of Cellophane.

Manufacture of Viscose Rayon :

Viscose rayon is a fiber of regenerated cellulose, it is structurally similar to cotton but may be produced from a variety of plants such as soy, bamboo, and suger cane, Cellulose is a linear polymer of β-D-glucose units with the empirical formula (C6H10O5)n. To prepare viscose, dissolving pulp is treated with aqueous sodim hydroxide (typically 16-19%w/w) to form "alkali cellulose," which has the approximate formula [C6H9O4-ONa]n. The alkali cellulose is then treated with carbon disulfide to form sodium cellulose xanthate.

                        [C6H9O4-ONa]n + nCS2 → [C6H9O4-OCS2Na]n

Rayon fiber is produced from the ripnened by treatment with a mineral acid, such as sulfuric acid. In this step, the xanthate groups are hydrolyzed to regenerate cellulose and release dithiocarbonic acid that later decomposes to carbon disulfide and water.

[C6H9O4-OCS2Na]2n + nH2SO4 → [C6H9O4-OH]2n +2nCS2 + nNa2SO4
                                      H2COS2 → H2O + CS2

Aside from regenerated cellulose, acidification given hydrogen sulfide, sulfur. and carbon disulfide. The thread made from the regenerated cellulose is washed to remove acid. The sulfur is then remoyed by the addition of sodium sulfide solution and impurities are oxidized by bleaching with sodium hypochlorite solution.

Wednesday, December 16, 2015

Wet-Dry-Melt-Gel Spinning Fibers Process Solutions

Wet-Dry-Melt-Gel Spinning Fibers Process Solutions

Wet Spinning :

Wet spinning is the oldest process. It is used for fiber-forming substances that have been dissolved in a solvent. The spinnerets are submerged in a chemical both and as the filaments emerge they precipitate from solution and solidify. Because the solution is extruded directly into the precipitating liquid, this process for making fibers is called wet spinning. Acrylic, rayon, aramid, modacrylic and spandex can be produced by process.

Dry Spinning :

Dry spinning is also used for fiber -forming is solution. However, instead of precipitating the polymer by dilution or chemical reaction., solidification is achieved by evaporating the solvent in a stream of air or inert gas.

The filaments do not come in contact with a precipitating liquid, eliminating the need the drying and easing solvent recovery. This process may be used for the production of acetate, triacetate, acrylic, modacrylic, PBI, spandex, and vinyon.

Melt Spinning :

In melt spinning, the fiber-forming substance is melted for extrusion through the spinneret and then directly solidified by cooling. Nylon, olefin, polyester, saran, and sulphur are produced in this manner. Melt spun fibers can be extruded from the spinneret in different cross-sectiona shapes ( round, trilobal, pentagonal, octagonal, and others ). Trilobal-shaped fibers reflect more light and give an attrative sparkle to textiles.

Gel Spinning :

Gel spinning is a special process used to obtain high strength or other special fiber properties. The polymer is not in a true liquid state during extrusion. Not completely separated as they would be in a true solution, the polymer chains are bound together at various points in liquid crystal form. This produces strong inter-chain forces in the resulting filaments that can significantly increase the tensile strength of the fibers. 

The filaments emerge with an unusually high degree of orientation relative to each other further enhancing strength. The process can also be described as dry-wet spinning, since the filaments first pass through air and then are cooled further in a liquid bath . Some high-strength polyethylene and aramid fibers are produced by gel spinning.

To be continue.......

Tuesday, December 15, 2015

The Manufacturing of Synthetic Fibers and Availability

The Manufacturing of Synthetic Fibers and Availability

Fineness of Staple :

A fiber must possess sufficient fineness of staple to be useful in the production of spun yarns. The principle fibers all have small diameters and a large number of them can be twisted together to yield a fine thread. Other things equal, the finer the staple of the fiber, the finer the yarn which can be produced form it. 

Porosity; Capillarity :

By this is meant that the fiber should be capable of easily adsorbing liquids and solutions and of permitting these thoroughly to permeate its substance. This property is important as it allows of the dyeing, bleaching, and otherwise preparing the fibers by modifying their natural condition.

Luster :

A further quality, which under certain conditions enhances the value of a textile fiber, is luster. Fiber possessing this quality to a marked degree, such as silk, mercerized cotton, and certain kinds of wool, are capable of producing a wide variety of beautiful effects.

Commercial Availability :

The second feature to which reference is made has principally an economic significance. In order to possess commercial value a fiber must be available in large quantity, and its supply must be more or less constant and readily marketed.

Synthetic Fiber :

Synthetic fibers or fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air and water forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were made from polymers obtained from petrol chemicals. These fibers are called synthetic fibers and and also called artificial fibers . Some of the fibers are made from plant cellulose. They are called as "cellulose fibers"

Manufacturing of Synthetic Fiber :

The fiber-forming polymers are solids and therefore must be first converted into a fluid state for extrusion. This is usually achieved by melting, if the polymers are thermoplastic synthetics. There are four methods of spinning filaments of manufactured fibers, wet, dry, melt, and gel spinning.

To be continue.....

Wednesday, December 9, 2015

Classification & Definition of Textile Fibers

Classification & Definition of Textile Fibers

Textile :

The definition of textile is something related to fabrics or the fabric industry. textile is defined as cloth or woven or knitted fabric.

A piece of heavy linen that you buy in order to sew a dress is in example of a textile.

Classification of Textile Fiber :

Generally two types of Textile fiber-
1. Natural fiber.
2. Man made fiber.

Natural Fiber :

Natural fiber include those produced by plants, animals and geological processes. They are biodegradable over time. They can be classified according to their origin. 
Example : Vegetable, Animal Cotton.

Man-made Fiber : 

Synthetic or man-made fibers generally come from synthetic materials such as petrochemicals. But some types of synthetic fibers are manufactured from natural cellulose, including rayon, model, and the more recently developed Lyocell. Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified or derivatives cellulose such as the cellulose acetates. 
Examplie : Fiber glass.

Difference between Natural Fiber and Synthetic fiber : 

               Natural Fiber
                   Synthetic Fiber
1. All the natural fiber comes from nature.
1. Synthetic fibers are completely man made.
2. Length of the fiber is nature given.
2. The length of fiber is controlled by men
3. Fibers are found in shape or filament form.
3. It is found in filament form but sometimes it could be converted into shape or cut length.
4. No need to spinneret for spinning process.
4. Spinneret is essential for filament production.
5. No need of chemical solution for yarn production.
5. Chemical solution is essential for yarn production.
6. Natural fabric is comfortable to wear.
6. Synthetic textile product is not as comfortable as natural product.

General Properties of Textile Fiber :

Tensile Strength :

There are a number of fibers, especially among the vegetable class ( such as those of the common milkweed, etc ). Which might prove of considerable value but for their lack of sufficient tensile strength. Although dependent also on other qualities, the resistance of a fiber to use and wear is primarily dependent on its tensile strength.

Length of Fiber :

The second important quality which determines the usefulness of a textile fiber is its length. Where a continuous thread is to be made up of a large number of individual elements, these elements must possess a considerable length with reference to their thickness, otherwise it would not be possible to make a thread that would hold together. In a general way and other conditions being equal, the strength of such a thread will be directly proportional to the length of the individual fiber elements employed.

Cohesiveness :

A third essential quality for a textile fiber is cohesiveness. By this is meant the property of the individual fibers cohering or holding on to one another when spun into a yarn. This is usually brought about by the surface of the surface of the fibers possessing a high degree of frictional resistance.

Pliability; Elasticity :

Another quality which is very essential to a satisfactory textile fiber is pliability, which permits of one fiber being easily wrapped around another in the spinning operation. The pliability of a fiber also determines on great measure its elasticity and resiliency, qualities which are often of prime importance in the manufacture of textile fabrics. Lack of these properties will make the fiber and its resulting products brittle and unyielding, and hence greatly limit the field of its usefulness.

To be continue.......