1. The one important characteristic of these fibres is their extreme fineness. Filaments as fine as 1.33 deniers are produced regularly ( as compared to viscose rayon which have a usual denier of around 2.5). This increased fineness is due to the stretch that is applied to the filaments during spinning. 2. Because of its fineness, cuprammonium rayons produce a soft silk like handle. 3. It has all the properties of cotton except that the averag e DP is lower and a larger portion of this fibre is occupied by amorphous regions. Hence the rayon swells to a greater extent and hence chemical reactions take place faster in the case of rayon than in case of cotton. 4. Like viscose rayon it burns rapidly and chars at 180 deg C. It is degraded and weakened by exposure to sunlight in the presence of oxygen and moisture. On ignition, it leaves behind ash containing copper. 5. The average tensile strength of cuprammonium rayon is 1.7-2.3 in dry and 0.9-2.5 in wet state. 6. It has an elongation at break of 10-17% when dry. 7. Moisture content at 70 deg F and 65% RH is about 11% as in case of Viscose Rayon. 8. Dye absorption power for direct dyes of cuprammonium rayon is i s greater and shades obtained are deeper than viscose rayon. 9. The filaments appear uniform with surfaces having no markings, in the longitudinal longi tudinal view. Cross sections are round and smooth with occasionally slightly oval.
(Like Viscose Rayon, cuprammonium rayon is al so a regenerated cellulose fibre. Cotton linters are used as the source of cellulose for this rayon. Ammonical copper oxide solution is also known as cuprammonium hydroxide solution. Cuprammonium hydroxide solution is a solvent for cellulose. When a solution of cellulose in cuprammonium hydroxide is diluted with water or treated with dilute sulphuric acid, the cellulose is regenerated or reprecipitated. By using a spinnerette, filaments of this regenerated cellulose can be produced. Manufacture of Cuprammonium Rayon The source of cellulose for this rayon is cotton linters, the purification of cotton linters is carried out in
two stages: a. Mechanical Treatment b. Chemical Treatment Mechanical Treatment The cotton linters are transported in bales in highly compressed state and the object of the mechanical treatment is to loosen them and to remove mechanically admixed and loosly bound impurities such as dust sand, seed residues etc. Chemical Tratment The mechanically opened and purified cotton linters are boiled under pressure for several hours with dilute sod ash ( Na2Co3) solution (2%) to which a little amount of caustic soda may be added. The natural fatty matter present in the cotton is converted into soluble substance by the action of soda ash and thus removed from cotton linters. Dissolution of Cellulose In this, a solution of hydrated copper sulphate in 300-400 liters of water is introduced in a vessel at ordinary temperature with stirring. Some sugar is also added followed by caustic soda solution to form copper hydroxide. Ground linters suspended in water are added to the above mixture to form copper cellulose. The copper cellulose is filtered to remove the l iquid, well ground and dissolved in a solution of ammonia in water. Spinning Solution By adding certain compounds to the cuprammonium cellulose solution, the solution is made more suitable for spinning. These compounds include glycerine, glucose, tartaric acid, citric acid, oxalic acid, can sugar etc. Stretch Spinning In the spinning process, the cuprammonium cellulose solution is discharged through nozzles ( spinnerette) into a solution of sulphuric acid in the form of relatively thick threads which are subsequently pulled( stretched ) to very fine filaments.)
Rayon is a manufactured regenerated cellulose fiber . Because it is produced from naturally [1] occurring polymers, it is neither a truly synthetic fiber nor a natural fiber ; it is a semi-synthetic [2] or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high luster quality giving it a bright sheen, Schweizer's reagent is the chemical complex tetraamminediaquacopper dihydroxide,
[Cu(NH3)4(H2O)2](OH)2. It is prepared by precipitating copper(II) hydroxide from an aqueous solution of copper sulfate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia. When the entire amount of copper is precipitated as hydroxide, it is a goo d idea to filter it and dispose of the filtrate and rinse the precipitate from sulfate and other excess ions. It forms a deep azure solution. If the solution is evaporated, it leaves light blue precipitate of copper hydroxide. This is because the formation of the tetraminocupric complex is reversible and ammonia evaporates together with the water. If the evaporation is conducted under stream of ammonia, then deep blue needle-like crystals are formed. These crystals should be kept in isolation or in ammonia atmosphere. Schweizer's reagent finds use in production of cellulose products such as rayon and cellophane, because wood-pulp, cotton fiber, and o ther natural cellulose sources are soluble in the solution. Dissolved cellulose precipitates when the solution is acidified.
PRODUCTION OF CUPRAMMONIUM RAYON
PURPOSE
In this demonstration rayon fiber is produced by the use of four common substance: sodium hydroxide, ammonium hydroxide, copper sulfate, and paper. This method demonstrates one of the earliest techniques of producing this famous polymer, called cuprammonium rayon. DESCRIPTION
This demonstration is appropriate for a general or first-year college-prep course. It shows the students the method of preparation of one of the first mass-produced synthetic fibers. It would fit very well with the organic sections found in most introductory texts. TIME R EQUIR ED
One class period. MATERIALS
Chemicals CuSO4·5H2O* NaOH* concentrated NH3 solution 1.6 M H2SO4 (88.8 ml of concentrated H2SO4 solution diluted to 1.00 liter with distilled or deionized wat er)* 11.0 cm filter paper* Equipment 250-mL Erlenmeyer flask 1000-mL beaker syringe or bulb/pipet combination funnel filter paper funnel support magnetic stirrer (optional) Buchner funnel and filtering flask (optional) *See Modifications/Substitutions HAZARDS
Avoid skin contact with all reagents. Use caution when making NaOH and H2SO4 solutions; both processes are exothermic. Avoid breathing NH3 vapors and work within hood if possible. Goggles must be worn for this demonstration. MODIFICATIONS/SUBSTITUTION
1. 2. 3. 4.
CuSO4·5H2O can be purchased as root killer at a garden supply store. NaOH can be purchased as lye in grocery stores. Sulfuric acid is available from auto supply stores as battery acid. This solution is 4.8 M. Paper towels could be substituted for the shredded filter Paper in this reaction.
PROCEDUR E
1. Dissolve 25.0 g of CuSO4·5H2O in 100 mL distilled water. Heat the water to accelerate the dissolving process. 2. Dissolve 8.0 grams NaOH in 200 mL distilled water. 3. Mix the cooled NaOH solution with the copper sulfate solution. Collect the resultant gelatinous precipitate of Cu(OH)2 by filtration. Wash the precipitate with three 10-mL portions of distilled water. If using 11.0 cm filter paper, several filtrations will be required because of the large amount of precipitate produced. 4. Measure 70 ml concentrated NH3(aq) into a 250-mL Erlenmeyer flask. Shred four pieces of 11.0-cm filter paper. Add the Cu(OH)2 precipitate carefully along with the filter paper to this flask and stir. This should result in a deep purplish-blue solution of tetraaminecopper(II) hydroxide, referred to as Schweizer's reagent. Stopper the flask and stir periodically for 24 hours. Use a magnetic stirrer, if available.
5. Take up the contents of the 250-mL Erlenmeyer flask in 10-mL increments in a 10-mL or 50-mL syringe. Squeeze out the contents into a 1000-mL beaker containing 300 mL of 1.6 M sulfuric acid. Be sure that the tip of the syringe or pipet is under the surface of the acid. A crude "thread" shou ld form. 6. The clumps or threads can be washed free of the solution to show the white color of the rayon. DISPOSAL Flush
the ammonia solution and the sulfuric acid solution down the drain with cop ious amounts of water. Dispose of rayon with solid waste. DISCUSSION
The primary reactions involved are: NaOH(aq) + CuSO4(aq) Cu(OH)2(aq)
Cu(OH)2(s) + Na2SO4(aq)
2+
-
Cu (aq) + 2 OH (aq)
2+
n Cu (aq) + (cellulose)n + 2n OH
-
(CuC6H8O5)n + 2n H2O
Cellulose is actually dissolved in [Cu(NH3)4](OH)2 solution and then regenerated as rayon when extruded into sulfuric acid. TIPS
1.
Filtration
of Cu(OH)2 can be a problem; small amounts of precipitate should be filtered and then combined in one container. 2. Samples of rayon and other synthetics could be shown and their prop erties discussed. Good morning everybody, today we're going to synthetize cuprammonium rayon by chemicals available at home without problems. The experience it's j ust meant to illustrate how a polimerization process works and to explore the science so don't expect to get a fine or useful product. rayon is a manufactured regenerated cellulose fiber. Since it's produced from natural occurring polymers it is neither synthetic fiber nor a natural one: it is a semi-synthetic fiber. There are three of more methods to make it: but just one is available at home: cuprammonium rayon. Warning: sodium hydroxide is corrosive, ammonia's fumes are toxic, plaese wear gloves and work outside or in a fumehood. Let's start with two solutions of very cold distilled water, about 60 ml for each beaker. In the first one on the left put 8 grams of copper sulphate pentahydrate, in the second one on the right 4 grams of anidrous sodium hydroxide. Now mix til they are completely dissolved. Working fast add the sulphate solution to the other one: a pre cipitate of copper hydroxide forms instantly. This is the reaction: CuSO4 + 2NaOH ---- Cu(OH)2 + Na2SO4 After filtrate with a paper filter the hydroxide and put it into a larger beaker full of ice. Infact it is
important to keep copper hydroxide cold for the next step or it will decompose into copper oxide unuseful for this reaction. After add about 50 ml of 30 % concentrated ammonia. Copper hydroxide solves into ammonia to form the deep blue coloured complex called schweitzer's reagent [Cu(NH3)4](OH)2. This complex is able to solve cellulose. After this passage put some paper into the cuprammonium complex and the mix. The blue liquid will become something like a jelly: it means it's ready for the next step. Into a largew container now put a solution of 5-10 % sulfuric acid solved into water. then with a syringe without needle take a part of the jelly and make it forms wir es upon the acid bath: rayon forms instantly. If you wanna get more fine wires put the needle to the syringe after you charged it, or it will block. as you can see rayon appears like small blue larvas. It's pretty cool to touch it and to play with it. Wires are platic and soft and they break very easely. wash rayon fibers obtained with water: the colour will pass from blue to white. Let it dry and now you have cuprammonium rayon.
