Regenerated cellulose is: (a) Nylon (b) Polyester (c) Rayon (d) Teflon
Hint: The fibre made from regenerated cellulose has many comfort properties as that of the natural fibres and can be easily dyed in different types of colours. It also has the lowest elastic recovery for any fibre.
Complete answer: Regenerated cellulose comes from natural sources of cellulose such as wood and other products. The molecular structure of regenerated cellulose is the same as that of the cellulose. Rayon is made from regenerated cellulose. The process involves the dissolution of cellulose and then regenerating the insoluble fibrous cellulose. There are several methods that are used: Cuprammonium method: This method involves the treatment of the cellulose with Schweizer’s reagent (copper and ammonia) which gives rise to cuprammonium rayon whose properties are very similar to that of the viscose. Viscose method: In this process the cellulose is treated with a strong base. The resulting solution is reacted with carbon disulphide which produces the xanthate derivative which is reconverted to cellulose fibre. This method gives rise to viscose rayon. Lyocell method: In this method, the cellulose is dissolved in N-methylmorpholine-N-oxide. This method is very expensive since it does not use carbon disulphide (very toxic) used in the viscose method. Lenzing’s Tencel is a lyocell fibre made by using the lyocell method. Rayon as a fibre has many of the comfort properties that are possessed by the natural fibres. It can have similar texture as that of silk, cotton, wool and linen. Rayon fibres are ideal for hot and humid climates since they do not insulate body heat. But they also have certain disadvantages such as low durability, low elastic recovery. So, the correct answer is “Option C”.
Note: In viscose method we can use wood as a source of cellulose. The other methods require lignin free cellulose; therefore viscose rayon is quite cheap. Modal is a type of rayon and two variants are available namely ‘polynosics’ and ‘high wet modulus rayon’.