PREPARATION OF RAYON
BY CUPRAMMONIUM PROCESS
Cellulose is the chief structural component to which plants owe their rigidity and form. Cellulose is natural polymeric material having fibrous structure. It is the principal component of the covering of plant cells. Cellulose represented by the formula (C6H10O5) is a linear polymer containing glucose units. Wood, cotton and other plant materials are the main sources of cellulose. In the pure form cellulose is present in cotton(98%) while in wood it is about 50% of the mass of dry wood.
Cellulose can be converted into cupra silk, acetate rayon and viscose rayon depending upon the method of treatment it undergoes while forming rayon. Between 1890 and 1895, German scientists Fremery and urban developed the manufacture of rayon from cellulose. They based their process on the observation that cellulose is soluble in ammoniacal copper oxide and can be regenerated from solution by adding acid. Cellulose is an insoluble material; however it is found to dissolve in cuprammoniam complex..[Cu(NH3)4](OH)2, known as Schweitzer’s reagent. It is regenerated from solution by adding sulphuric acid. Thus rayon is ‘regenerated cellulose’ and it is used for making fabrics like stockings, shirts etc.
Aim of the projects
The main objective of the project is to illustrate the preparation of rayon by the cuprammonium process. Instead of wood pulp as the cellulose source, attempt is done to make use of raw cellulose products such as waste paper(un-printed), filter paper etc.
Apparatus and chemicals
Sodium hydroxide solution
50% Ammonia solution
Filter paper strips
until a precipitate is formed. Add NaOH solution to complete precipitation. Filter off the precipitate and wash it with water two or three times until the washing does not give a precipitate with barium chloride solution. Tranfer the precipitate into a beaker and add 50 ml. of liquid ammonia.. The precipitate dissolves giving a deep blue transparent solution. This is known as Schweitzer’s reagent.
Cut few filter paper strips (about 1g) intosmall pieces and add them into the cuprammoniam reagent taken into a conical flask. Close the flask with a cork and keep it over night. When all the pieces of filter paper have dissolved, the solution will be viscous(called viscose).
The viscous solution is drawn into a syringe. Keeping the nozzle of a syringe inside 5M sulphuric acid solution taken in a beaker, the solution in the syringe is forced into the acid solution. Move the nozzle of the syringe in the acid solution continuously to form long filaments of rayon in the acid solution. The beaker containing rayon fibers is allowed to stand undistributed until the blue colour of the rayon filaments disappears and becomes white. Remove the rayon threads from the acid bath, wash with water and dry using filter paper.
Mass of filter paper strips used = …..g
Mass of rayon thread formed = ……..g
|Author: sharad||Member Level: Bronze||Revenue Score: |
|i need more detail of about 20 pages on various methods|