Cellulosic Fibers - Bast Fibers PDF

CELLULOSIC FIBERS BAST FIBERS  FLAX FIBRE (LINEN) Flax is a filament fiber harvested from flax plants that when made into fabric, is called linen. Flax is the oldest fiber on record, first grown by the Egyptians having along the banks of the Nile. The term “linen” i...

CELLULOSIC FIBERS BAST FIBERS  FLAX FIBRE (LINEN) Flax is a filament fiber harvested from flax plants that when made into fabric, is called linen. Flax is the oldest fiber on record, first grown by the Egyptians having along the banks of the Nile. The term “linen” is often misused, being applied to fabrics that simply look like linen, or being used as a general term for sheets, towels, and tablecloths. Flax fibers are obtained from the stem of the flax plant. The stem consists essentially of a central woody core and a surrounding cortex which contains the flax or bast fibers. The fibers are obtained from the plant in the form of long filaments, each of which is made up of cells. Linen is one of the oldest and a very popularly used fiber obtained from the stalk of the flax plant. The hair like fibers, are held together by a gummy substance known as pectin. Linen is composed of 70 percent cellulose, and 30 percent pectin, woody tissue, ash and moisture. Physical Characteristics The fiber is smooth, straight and lustrous. It is more brittle and less flexible than cotton. The fiber is also more difficult to spin into yarn. It has a long staple fiber length when compared to cotton. Major Producers Western Europe is the major producer of finest quality linen, China is also one of the leading producer of high quality linen. Ireland, Italy and Belgium are other significant producers. Belgium produces the best quality linen, and Ireland is known for its craftsmanship. ADVANTAGES OF LINEN FABRIC: Excellent strength gains strength when wet Hydrophilic: absorbs water and dries quickly Cool in warm weather Washable Withstands very high temperatures when washing and ironing No static, pilling, or lint problems Unique texture from the thick-and-thin pattern of the fibers DISADVANTAGES OF LINEN FABRIC: Wrinkles very easily Fair abrasion, low durability Poor drape and elasticity Expensive Generally, flax is harvested 30 to 35 days after flowering—usually in the second half of July. Several visual factors are used to determine whether the flax is ready. The stalks are beginning to turn yellow, but there is still some green in them; there are a few flowers still visible, but most have dropped, leaving pale brown seed balls behind. The timing of the harvest affects the final product. The optimal window for harvesting may be only a day or two, so it is important that farmers time it correctly. Harvesting just a few days after flowering results in a fine flax fiber—the longer the wait, the coarser the fiber will be. Harvesting too early, however, results in unripe seeds that can't be used to start new plants. Waiting too long—until the plants turn dry and brown—results in a brittle fiber, unsuitable for textile production. PROCESS 1. Rippling: The stem for the fiber is pulled out by hand or machines while the roots are still intact or else the fibers get permanently discolored. Stem are passed through special machines to remove seed pods. 2. Retting: To obtain fibers from the stalk one must remove the outer woody portion – done by retting. Retting can be done in fields (dew retting) in stagnant ponds or pools (water retting or pool retting), where the temperature and bacteria count can be carefully controlled. When special enzymes or chemicals (sodium hydroxide) are added to the water it is called chemical retting. This type of retting is much faster than any other type of retting. 3. Scutching: After the outer woody portion of the stems has rotted during retting, the stems are dried and passed through the metal roller which crushes the woody portion and the fibers are exposed. 4. Hackling or Combing: The fibers are combed to remove any remaining woody portion and arrange them in a parallel fashion. This also helps in separating long & short fibers. 5. Spinning: The fibers are then drawn into yarns and spun.The spinning process comprises various operations which make it possible to transform the fibers into yarn. There are two main techniques: thick yarns for decoration are obtained by dry spinning; Fine yarns for clothing and household linen, by “wet” spinning. 6. Cottonizing: This reduces the bast fiber to the length similar to that of cotton fiber. These cottonized fibers can be processed on equipment designed for cotton. All the bast fibers – jute, flax, ramie, hemp can be cottonized. Properties of Linen 1. Microscopic Properties: Cross–section is polygonal in shape. The longitudinal view does not show any convillsions as in cotton but irregular joint formations called nodes. 2. Physical Properties: (a) Lusture - High (b) Resiliency - Poor; wrinkles easily. (c) Moisture Absorption - Very good. 3. Chemical Properties: (a) Resistance to Acids - Good (b) Alkalis - High Resistance (c) Sunlight - Good 4. Biological Properties: a) Microorganisms Attacked by mildew b) Insects Not palatable for insects. 5. Thermal Properties: (a) Reaction to Heat Decomposes above 150 degree C. (b) Flame Burns readily and leaves almost no or little residue. Smells of burning paper. END USES OF LINEN FABRIC: Apparel: suits, skirts, jackets, dresses Interiors: tablecloths, napkins, wallpaper PROTEIN FIBERS  NATURAL PROTEIN FIBRE Natural protein fibers are of animal origin. This includes the hair (wool, specialty hair, fur) and secretions of animals (silk, spider silk). Two major classes of natural protein fibers exist and include Keratin (hair or fur) and Secreted (insect) fibers. The protein present in wool is keratin, whereas that of silk is fibroin.  WOOL FIBRE Wool fiber is a natural animal fiber which is derived from the hair grown on sheep; it is composed of a protein substance called Keratin which is the major component of wool fiber. Wool is also composed of hydrogen, nitrogen and carbon, wool is the only natural fiber which also consists of sulfur in addition. Wool gives a spongy feel and acts as a good insulation material due to the presence of curls or crimps in its structure which is beneficial to the user. Wool’s natural crimps allow the fibers to hold together and create a very strong yarn, also creating air pockets that act as a natural layer of insulation and making it very desirable to wear in cooler weather. Growth and Harvesting of Wool fiber: Wool is amongst the oldest fibers known to humans and it was one of the first fibers to be spun into the yarn and then woven into fabric. Wool not only comes from sheep, but also from different animals such as goats, camels, alpacas etc. The major producers of wool are China, Australia, Eastern Europe and New Zealand. Production of wool in India: The woolen industry in the country is small in size and widely scattered. It is basically located in the States of Punjab, Haryana, Rajasthan, Maharashtra and Gujarat. 40% of the woolen units are located in Punjab, 27% in Haryana, 10% in Rajasthan, while the rest of the States account for the remaining 23 % of the units. THE MANUFACTURING PROCESS OF WOOL To provide the finest quality of wool, the sheep are inoculated against diseases, given good nutritious diet to produce healthy animal so that the quality of wool is good. The process of removing hair from the sheep is termed as SHEARING. It is done manually by using a pair of scissors or electrically driven shavers. In this process when hairs are removed from the live sheep, known as clipped wool or fleece. When it is obtained from dead sheep it is known as pulled wool. A female sheep can produce 20 pounds of wool where as a male sheep can produce 15 pounds of wool. The sheared wool is called as the raw wool and the very first step is cleaning of the wool to get rid of all the impurities, dust and other unwanted materials. The sheared skin with hairs is thoroughly washed in large tanks to remove grease, dirt, and dust. This process is known as SCOURING. Next, the wool is graded for fineness and length. GRADING is evaluating the whole fleece for fineness and length.  The hairy skin is sent to industries where hairs with various textures are separated or sorted. The small fluffy fibres are called burrs. These burrs are picked out from the hair. SORTING process is done to separate different qualities of wool. One best quality wool comes from the sides shoulder and back and the poorest wool comes from the lower legs. Fineness, color, crimp, strength,length and elasticity are characteristics that may vary with the breed of sheep. Wool fibres are carded by passing them between cylinders faced with fine wire teeth. Wool CARDING is the process of brushing the wool fibres to organize them. This procedure removes considerable vegetable matter – such as twigs and burrs that remain in the fibre after scouring – and begins to disentangle the fibres and straighten them. Types and kinds of Wool Fibers + Specialty Wool The term wool legally includes fiber from sheep, angora and Cashmere goats, camel, alpaca, llama and vicuna.Lamb‘s wool comes from animals less than seven months of age. Virgin Wool: Wool that has never been processed. Recycled wool: Scraps of woven or felted fabrics is shredded, sorted, cleaned, respun and woven. Different breeds of sheep bore different types of wool. There are various types of wool out of which the best quality of wool is obtained from merino sheep. Varieties of animals like: Angora wool (Rabbit) Cashmere wool (Goat) Chiengora Wool (Dog) Llama wool (Llama) Lopi (Icelandic sheep) Mohair (Angora goat) Pashmina (Pashmina goat the Changthangi or Kashmir Pashmina goat) Shahtoosh (Tibetan Antelope) is domesticated in order to obtain wool from them. Out of which angora wool, mohair and cashmere wool are of sheer prominence. Specialty Wool Goat family- Angora goat (Mohair) Cashmere goat Capra Hircus goat (Pashmina) Camel family- Camel Llama Alpaca Vicuna Guanaco Others- Angora Rabbit Fur Fiber Musk ox Yak Microscopic Properties: Longitudinal View: Cylindrical, irregular, rough surface, scale-like structure, dark medulla may appear on coarse wool fibers Cross-Sectional View: Nearly round or circular, medulla (a centrally placed core in the cortex and consists of a ladder of cells separated by gaps of air)may be visible. Physical Properties: a) Lustre- Medium b) Shape- As shown; wool has natural crimp. c) Resiliency- Excellent. Has a good elastic recovery and bounces back to shape. d) Moisture Absorption- Good. Diagram of wool fiber crimp and three dimensional close-up of the fiber Thermal Properties: (a) Resistance to Heat: Avoid exposure over 140 C because the protein gets denatured at high temperatures. (b) Resistance to Flame: Self–extinguishing and smells of burning hair. Biological Properties: (a) Resistance to Microorganisms: Not attacked by mildew or rot. (b) Resistance to Insects: Attacked by moths and carpet beetles. Chemical Properties: (a) Resistance to Acids: Good (b) Resistance to Alkalis: Poor–reason why wool is washed with Ezee or Genteel (slightly acidic). (c) Resistance to Sunlight: Prolonged exposure destroys the fiber. Application of Wool Fiber: Being easy to clean and lasts long, preferred for clothing. The most important use of wool is for apparel coats, jackets, suits, dresses, skirts, slacks made from woven fabrics of varying weights and knitted fabrics. Acts as insulator, hence used for bedding and blankets. Used to line boxes, shelf linings and surfaces required to be softer. In the home furnishing area, the major use of wool is in carpets and rugs where wool is used more, cover to the carpets and warm in the rugs. Wool is widely used for a variety of apparels all over the world. Also used for making carpets and rugs. The wool fibers trap air and form an insulating layer for the body thus making wool a warm fiber. It is also naturally crease resistant and absorbent making it comfortable to wear. Care of wool is difficult because it has tendency to matt up. The scales present on the wool fiber entangle with each other forming into gook like structure. This causes the matting and thus shrinkage of wool. This property of matting is responsible for production of felts.