Viscose - Definition of Viscose

[...]... alkali → Converts Na- cellulose Xanthate to regenerated cellulose 1% Causes variation in strength, excess use degrades quality → of viscose It causes serrated X- section so that the dye absorbency increased 2% → Proper recipe of a coagulating bath during spinning Na2SO4 - H2SO4 - ZnSO4 - Glucose Water Temperature - 69% - 40o55oC Given pliability and softness of the yarn, increase viscosity of bath, control... at (4 0-5 5) C PHYSICAL PROPERTIES: Elongation at Break: High tenacity rayon has only 9-1 7% elongation at break but ordinary Viscose rayon has 1 5-3 0% elongation at break Resiliency: The resiliency nature of viscose fiber is low Dimensional stability for HWM is high Colour & luster: The color of viscose is white & no colour Luster is high Softening temperature: At 14 9-1 63˚C viscose fiber will be soft Specific... moisture than cotton For Viscose Rayon is 13% moisture absorbs at 21˚C Elasticity: The elasticity of Viscose Rayon is less than 2-3 % Action of Heat At 150˚C or more, Viscose Rayon loses its strength and begins to decompose at (17 5-2 04) ˚C Raw materials of viscose rayon fiber: 1 Wood 2 Seed hair 3 Bast 4 Grasses 5 Leaf 6 Bamboo Manufacturing process of Viscose rayon: Preparation of wood pulp: Wood chips... Structure of unit cell of cellulose Chemical Composition of Viscose PHYSICAL PROPERTIES: Density: The density of Viscose rayon is 1.53 g/cc Rayon filaments are available in three densities: 1.5, 3.0 and 4.5 Tensile Strength: The Tensile Strength of the fibre is less when the fibre is wet than when dry It is 1. 5-2 .4 gpd in the dry state and 0. 7-1 .2 gpd in the wet state Stiffness: Normally the stiffness of viscose. .. gravity of viscose rayon is 1.5 CHEMICAL PROPERTIES: Effect of Acid: Similar to cotton fibre Viscose rayon is attacked by hot dilute or cold concentrated mineral acids (H2SO4, HCl), which weaken and disintegrate the fibre Effect of Alkalis: Like cotton, Viscose rayon has a high degree of resistance to dilute alkalis Strong solutions of alkali cause swelling, with loss of tensile strength [] Effect of Bleach:... Description of Viscose manufacturing: Steeping & Pressing: The flat, white sheets of board contain about 90 to 94% of pure cellulose The sheets are then stacked vertically in the press and then soaked in a 17.5% solution of caustic soda for 1-4 hrs This process is known as Steeping Then the excess alkali is pressed out Description of Viscose manufacturing: Shredding: The shredding m/c consists of a drum... manufacturing: Spinning: • Ripen viscose soln extruded through the spinneret mostly made of platinum alloys The jet of viscose enters a co-agulating bath containing the followed composition of mixture– Sulphuric acid – Sodium sulphate – Zinc sulphate Purification: The yarn collected in the Topham Box is impure and relatively weak, it has to be purified Purification consists of 4- operation – Washing – Desulphurising,... fibers of extra strength and reduced elongation Such fibers are designated as high tenacity rayons, which have about twice the strength and two-third of the stretch of regular rayon An intermediate grade, known as medium tenacity rayon, is also made Its strength and stretch characteristics fall midway between those of high tenacity and regular rayon Description of Viscose manufacturing: Preparation of. .. ageing – which is mainly a process of depolymerisation Churning: After ageing, the soda cellulose crumbs are introduced into rotating air-tight hexagonal churns About 10% of their own (crumbs) weight of carbon disulphide is added and the crumbs and disulphide are churned up together, a deep orange, gelatinous mass of sodium cellulose Xanthate is formed Description of Viscose manufacturing: Mixing (Solution):... dissolves to a clear-brown, viscous liquid, similar in appearance to honey this liquid is known as Viscose but is still too impure, too acetated and too young to spin Ripening: The viscose solution is stored for 4 to 5 days at 10o-18oC and during storage it ripens The test which is available to determine when viscose is ripe enough to be spun is as given below Acetic acid test: Description of Viscose manufacturing: . (degree of polymerization) of viscose polymer is (30 0- 450). Molecular weight of Viscose is 90,000 to 110,000 and number of glucose residues 550 to 680. According to ISO/TC6 the code of Viscose. manufactured fiber composed of regenerated cellulose in which substitutes have placed not more then 15% of hydrogen’s of the hydroxyl groups ** DEFINITIONS OF VISCOSE: Chemistry of Viscose Rayon Cellulose,. (Solution) • Ripening • Spinning • Drying Flow chart of viscose rayon manufacturing: STRUCTURE OF RAYON Fig . Structure of unit cell of cellulose The unit cell of cellulose is shown in Fig. Chemical Composition of Viscose Density: The