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Saturday, January 5, 2013

Synthesis of Rayon - Fibers - Lu Le Laboratory



Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic 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. (Wikipedia)

In the experiment, cellulose in filter is dissolved and, upon acidification, precipitated and regenerated as rayon.

 
Reaction

Copper hydroxide is prepared by reacting copper(II) sulfate with aqueous ammonia:

Cu2+(aq) + 2 OH- Cu(OH)2 (s)
                                                                                                                          Blue-Green
    
     The copper hydroxide reacts with additional aqueous ammonia to form tetraammoniecopper(II) hydroxide, Cu(NH3)4(OH)2 . The filter paper(cellulose) dissolves in this complex and is regenerated upon acidification as the polymer rayon. Rayon is insoluble in aqueous solution, so it precipitates when it is squirted in the aqueous acid solution.


Chemical

1.      Aqueous ammonia 28%: 100mL
2.      Copper sulfate


3.      Sulfuric acid
4.      Cellulose
 

Procedure

1.      Prepare this solution of copper(II) hydroxide prior to the demonstration:
a.       Place about 125mL of water in a 500mL beaker.
b.      Add copper sulfate and stir until the solution is saturated.

 
c.       With constant stirring, add concentrated aqueous ammonia drop by drop until a blue-green color appears and a precipitate forms. Do not add too much aqueous ammonia. If the solution becomes dark blue, start again. 

 Do not add too much aqueous ammonia or the solution would turn dark blue

 Copper(II) hydroxide is a cyan precipitate
 
2.      With 11-cm filter paper, filter the solution you have prepared to recover the copper(II) hydroxide. Wash it once and discard the filtrate.

 
3.      Place the filter paper and the filtrate in a second 125mL Erlenmeyer flask with a stopper. Shred two more pieces of filter paper and place these pieces in the flask also.

 
4.      Place the Erlenmeyer flask on a magnetic stirrer and add 100mL of concentrated aqueous ammonia. Continue stirring until the paper is all dissolved and the solution becomes thin enough to pour easily. This should take about 30 minutes. You may need to add a little more aqueous ammonia.

 After 1500rpm stirring, the solution become jelly

5.      Place 200mL of 0.5M sulfuric acid in a 400mL beaker.

 
6.      Carefully fill a dropper or syringe with the dark blue solution.
7.      Place the tip of the dropper beneath the surface of the acid in the beaker. Eject the  dark blue solution from the dropper.

 Rayon forms immediately

8.      Observe the rayon thread for a few minutes. Wash it several times. Dry it in room temperature. 

 The rayon appears blue at the first minutes

It becomes white after several minutes or stirring



After washing several times, it becomes white

It is the final product
 
References

1.      Lee R. Summerlin and James L. Ealy, Jr. (1988) Chemical Demonstrations A Source Book for Teachers Volume 1, Second Edition. Washington, DC: American Chemical Society.
2.      Wikipedia



13 comments:

  1. Hello,
    I would know if we can do the step number 4 if we don't have a magnetic stirrer.
    Thanks

    ReplyDelete
    Replies
    1. You can do this step in a PET bottle with some marbles or small pebbles (used as a sitrrer), and then shake it violently until paper is dissolved completely. Or you can just stir the mixture with a glass robe (very exhausting). Have fun~

      Delete
    2. Thank you so much. Just another question. This synthesis of rayon is by Cuprammonium method?

      Delete
    3. No problem. And you are right, it is produced by the Cuprammonium method so this rayon is also called "Cuprammonium rayon".

      Delete
  2. Hi,
    I have synthesized rayon with CuCO3 instead of Cu2SO4. I should be very grateful if you would show me which reaction takes place with CuCO3.
    Thanks a lot.

    ReplyDelete
    Replies
    1. In the reaction, tetraammoniecopper(II) hydroxide: Cu(NH3)4(OH)2, the copper complex which is really working in the reacting mixture. Whether CuCO3 or CuSO4 is only being a copper ion source. So you can use any copper(II) salt which can be dissolved in the aqueous ammonia. Have fun~ :D

      Delete
    2. By the way, you can also read this article it contains some information about the reaction. http://ncsu.edu/project/chemistrydemos/Organic/Rayon.pdf

      Delete
    3. Perfect! Thank you so much:D

      Delete
  3. Is there any method to determine whether the compound formed is rayon?? like some characteristic method or something???

    ReplyDelete
  4. good evening.

    sir why do we filter paper .
    please tell me

    ReplyDelete
    Replies
    1. Hi AMIT,
      Because filter paper does not like normal A4 paper which
      usually contains additives, likes alum. To ensure the purity of cellulose in
      the experiment, filter paper is recommended.

      Delete
  5. Textile Testing is an Important Part for a Textile Company as they need a quality certificate to export their Textile or Garment Products. Color matching cabinet

    ReplyDelete