1). Research one biopolymer from given assessment task sheet:

    ➢ Viscose Rayon

  Viscose Rayon is an artificial silk which is made from regenerated cellulose, which is usually obtained from cotton or wood pulp. These raw materials are treated to produce sheets of purified cellulose containing 87-98% cellulose. They are then bleached with sodium hypochlorite (NaOCl) to remove natural colour. The obtained cellulose is then subjected to a treatment to turn it into the biopolymer; viscose rayon. The purified cellulose is treated with an 18% sodium hydroxide solution before being shredded (or ‘crumbed’) and ‘aged’ for two or three days under controlled temperature and humidity. Liquid carbon disulfide (CS2) is then added to the ‘crumbs’ to change the cellulose into cellulose xanthate, which is a light orange substance (still in crumb form). It then forms a ‘viscose’ solution after being reacted with more sodium hydroxide (NaOH). To produce the actual rayon filament, the viscose solution is aged, filtered, and vacuum treated, which removes any air bubbles that could cause the filament to weaken and break. It is then pushed through holes in a spinneret into an acid solution (sulphuric acid [H2SO4]); this coagulates the cellulose xanthate to form “regenerated fibres” of 100% cellulose. The freshly formed viscose must then be purified and strengthened. It is thoroughly washed, and treated with a dilute solution of sodium sulphide to remove any sulphur impurities. It may then be bleached to remove a slight yellowness and then it is given a final washing.

  Because Rayon is made from cellulose, it has many properties similar to many natural cellulosic fibres, such as cotton. Rayon is good at absorbing moisture (even more so than cotton); it is breathable, and easily dyed in many colours. Rayon does not build up static electricity. Rayon is used in clothes due to its properties, and will not pill unless made from short, low – twist yarns (A continuous strand of...