Holidaygomework

Topics: Rayon, Cellulose, Sodium hydroxide Pages: 5 (948 words) Published: June 22, 2013
Aim To prepare a sample of cuprammonium rayon threads from filter paper Apparatus Required
a) Conical flask (preferably 250 ml)
b) Funnel
c) Glass rod
d) Beaker (preferably 250 ml)
e) Water bath
f) Filter paper
(Whatman paper or ordinary filter paper sheets. Preferably, Whatman)

Chemicals Required
a) CuSO4
b) NaOH solution
c) Liquor ammonia solution
d) Dilute H2SO4
e) Whatman Paper
f) Distilled H2O

Background
Rayon is a synthetic fiber produced from cellulose. Developed in an attempt to produce silk chemically, it was originally called artificial silk or wood silk. Rayon is a regenerated fiber, because cellulose is converted to a liquid compound and then back to cellulose in the form of fiber.

For example, cuprammonium rayon is made by dissolving cellulose in an ammoniacal copper sulphate solution.

The characteristics of rayon fibers are:

s They are highly absorbent,

s Soft and comfortable,

s Easy to dye

s Drape well.

Introduction

Rayon is a fiber produced from cellulose. It was the first man-made fiber, but it is not considered synthetic in the sense that petroleum-based fibers such as nylon or polyester are. It was originally called artificial silk and was developed in the late 1800s in France. Today it is made from the cellulose extracted from wood pulp.

The fabric made from Rayon fibers is similar in absorbency, breathability and drape to natural fabrics like cotton and linen.

You can make rayon in the laboratory as a chemistry exercise, but you will not be able to use the results to make fabric.

Cellulose is nature’s own giant molecule. It is the fibrous material that every plant from seaweed to the sequoia makes by baking glucose molecules in long chains; the chains are bound together in the fibers that give plants their shape and strength. Wood has now become the main source of cellulose. Since it contains only 40% to 50% cellulose, the substance must be extracted by ‘pulping’. The logs are flaked, and then simmered in chemicals that dissolve the tarry lignin, resins and minerals. The remaining pulp, about 93% cellulose, is dried and rolled into sheets-raw material for paper, rayon and other products.

It can be obtained in 2 ways:

Viscose Process: Cellulose is soaked in 30% caustic soda solution for about 3 hrs. The alkali solution is removed and the product is treated with CSi. This gives cellulose xanthate, which is dissolved in NaOH solution to give viscous solution. This is filtered and forced through a spinneret into a dilute H2SO4 solution, both of which harden the gum-like thread into rayon fibers. The process of making viscose was discovered by C.F.Cross and EJ.Bevan in 1891.

Cuprammonium
Rayon:

Cuprammonium rayon is obtained by dissolving pieces of filter paper in a deep blue solution containing tetra-ammine cupric hydroxide. The latter is obtained from a solution of copper sulphate. To it, NH)OH solution is added to precipitate cupric hydroxide, which is then dissolved in excess of NH/.

Reactions: CUSO4+ 2NH4OH — Cu(OH)2+ (NH4)2S04 Pale blue ppt Cu(OH) 2 + 4NH4OH — [Cu(NH3) 4](0H) 2 + 4H2O [Cu(NH3) 4](0H) 2 + pieces of filter paper left for 10-15 days give a viscous solution called VISCOSE.

Procedure

A. Preparation of Schweitzer’s Solution:

a) Way20gofCuSO).5H20.

b) Transfer this to a beaker having 100ml distilled water and add 15ml of dilute H2SO4 to prevent hydrolysis of CuSO).

c) Stir it with a glass rod till a clear solution is obtained. Add 11ml of liquor ammonia drop by drop with slow stirring. The precipitate of cupric hydroxide is separated out.

d) Filter the solution containing cupric hydroxide through a funnel with filter paper.

e) Wash the precipitate of cupric hydroxide with water until the filtrate fails to give a positive test for sulphate ions with barium chloride solution.

f) Transfer the...
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