Make Synthetic Fiber Production of Cuprammonium Rayon.

Introduction: (Initial Observation)

Long fibers of cotton (cotton lint) can easily be used to make cotton thread and cotton fabric; however, short fibers (cotton linter) and pulp can not be used to make thread or yarn. There have been many attempts by scientists to utilize such a large amount of short cellulose fibers. Finally scientists were able to convert shot fibers and pulp to long fibers known as cuprammonium Rayon. That was a start for the synthetic fiber industry.

The cuprammonium rayon fibers are manufactured in fine yarn and used, in large quantities, for tricot fabrics and thin fabrics, because they are flexible and in good tactile feeling to the human skin.

My question is “How can short fibers be converted to long fibers?”

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Project advisor

The experiment in this project requires expert adult supervision.

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.

Information Gathering:

As far back as 1664, English naturalist Robert Hooke theorized that artificial filaments might be spun from a substance similar to that which silkworms secrete to make silk. This was often tried by scientists in the ensuing years who sought an “artificial silk”, yet no one was to succeed until the Frenchman, George Audemars. By dipping a needle into a viscous solution of mulberry bark pulp and gummy rubber, he was able to make a thread. While interesting from a scientific standpoint, this process was hardly viable economically – it was very slow, and required a great deal of skill and precision. The first commercial synthetic fiber was produced by Louis-Marie-Bernigaud, Count of Chardonnet (1839-1924) after 29 years of research, was patented in 1884, and manufactured by him in 1889. Soon after, the English chemist Charles Frederick Cross and his collaborator Edward John Bevan discovered the viscose process (see below) in 1891 (1892?). Courtaulds Fibers produced the first commercial viscose rayon in 1905; the first in the United States was in 1910 by the American Viscose Company. Initially rayon was called “Artificial Silk”, and many other names. In 1924 (1926?), a committee formed by the U.S. Department of Commerce and various commercial associations decided upon the name “rayon”. It was called “rayon” for one of two reasons: either because of its brightness and similarities in structure with cotton (sun = ray, -on = cotton). Or because the naming committee couldn’t find a name from the thousands entered in a contest they sponsored, and who hoped to shed a “ray of light” on the subject (from rayon, French for ray).

Fiber Production

By using two different chemicals and manufacturing techniques, two basic types of rayon were developed – viscose rayon and cuprammonium. Other processes for rayon include the polynosic (modal) process and the now obsolete nitrocellulose and saponified acetate processes. The nitrocellulose process is likely obsolete not only because the viscose and cuprammonium processes are more effective, they are also safer; the nitrocellulose process results in a fiber with explosive properties.

As recently as 1992 there has been an entirely new process developed for producing regenerated cellulose fibers: the lyocell process, developed by Courtaulds. While it is sufficiently different from rayon to almost be in a class by itself, the U.S. Federal Trade commission has formally amended the textile rules to add lyocell as a subclass of rayon.

As viscose is the most common and recognized process for making rayon today, the process is outlined below. While the United States government considers fibers from all the above processes rayon, the International Organization for Standardization (ISO) prefers the name viscose for rayon (regenerated cellulose) obtained by the viscose process. The name viscose was derived from the word viscous, which describes the liquid state of the spinning solution.

Dissolution

The cellulosic raw materials for rayon are wood chips (usually from spruce or pine) or cotton linters. These are treated to produce sheets of purified cellulose containing 87-98% cellulose. They are then bleached with sodium hypochloride (NaOCl) to remove natural color. These cellulose sheets are then soaked in 18% caustic soda for 1 to 2 hours producing sheets of alkali cellulose. Any excess alkali is pressed out. The substance is broken up into flakes or grains called cellulose crumbs, which are aged for two or three days under controlled temperature and humidity. Liquid carbon disulfide is added to the crumbs to change the cellulose into cellulose xanthate, a light orange substance that is still in crumb form. These crumbs are dissolved in a weak solution of caustic soda and transformed into a viscous solution called “viscose”, honey-like in color and consistency.

Extrusion

To produce the rayon filament, the viscose solution is aged, filtered, then vacuum-treated to remove any air bubbles that could weaken the filament and cause it to break. It is then pumped through spinnerets into a bath of sulfuric acid, which coagulates the cellulose xanthate to form regenerated filaments of 100% cellulose. The many variations and different properties of viscose such as luster, strength, softness and affinity for dyes, are influenced here by varying the technique and by the addition of external materials.

Purification

Once extruded, the freshly formed viscose must be purified and strengthened. It is thoroughly washed, treated with a dilute solution of sodium sulfide to remove any sulfur impurities. It may be bleached to remove a slight yellowness and to secure even white color, and then given a final washing.

Cuprammonium Process

Cellulose in this process is instead treated with ammonia and cupric oxide. Rayon created by this process is also called cuprammonium cellulose or Cuprophan, cuprammonium rayon, or saponified cellulose ester. One interesting use of this variety of rayon is in the manufacture of artificial kidneys and semi-permeable membranes for hemodialysis. This is possible because cellulose and regenerated cellulose allow molecules of a certain size and/or chemical composition to pass through them, while blocking others. Harmful substances are strained out, and the blood is purified.

Lyocell Process

Lyocell was created by Courtaulds Fibers in 1992, and first manufactured in the United States in 1993. It is marketed under the Tencel(TM) name. In the lyocell process (also called “solvent-spun”), wood pulp and amine oxide solution are mixed and heated until the cellulose dissolves. The clear solution that results is then extruded into a dilute aqueous solution of the amine oxide, which precipitates the cellulose as fiber. After washing in water, the fiber is ready for finishing processes. The dilute amine oxide from washing is purified and recycled by evaporating the excess water. The difference between this process and other cellulose spinning methods are considerable. Lyocell production uses a non-toxic solvent that is recovered, purified and recycled as an integral part of the manufacturing process. Waste products are thus minimal and harmless. The process uses less energy, less water and less non-renewable resources. While lyocell is classified as a subclass of rayon (see above), it has numerous advantages over conventional rayon fibers. Lyocell is much stronger, washable, shrink- and wrinkle-resistant than rayon, thus overcoming rayon’s major faults. Yet it still has the soft hand and excellent drape of rayon, and its high absorbency, and excellent dye- and print-ability. Lyocell is environmentally friendly. It is produced from the wood pulp of trees specifically grown for this purpose. It is specially processed, using a solvent spinning technique in which the dissolving agent is recycled, reducing environmental effluents.

Fiber Structure

The structure of the rayon fiber is generally that of smooth, inelastic filaments like glass rods. However, different processes, additives and finishing techniques can vary the physical appearance and structure of the fiber.

Fiber Identification

In the burning test, rayon most resembles cotton. It ignites rapidly, sometimes even faster than cotton, burning with a large, bright, yellow flame. Burnt rayon leaves an odor like burnt paper, similar to cotton. The ash is also like cotton: light and feathery gray, which disintegrates rapidly.

In the feeling test, rayon is more difficult to identify. The variety of processes, modifications of technique and various treatments can make rayon look and feel like silk, cotton, wool or linen. In general, however, rayon has the smooth felling of silk. It is slippery because of the smoothness of the filaments, and has an almost brittle-feeling quality due to the fiber’s inelasticity.

The breaking test can differentiate between rayon, cotton and linen yarns. Because of its inelasticity, rayon will tend to break shortly, with a short, uneven breaking pattern. It is even easier to distinguish when wet, as it breaks very easily then.

Fiber Properties

General Characteristics: Rayon as a cloth is soft and comfortable. It drapes well, which is one of the reasons it is so desirable as an apparel fabric. Most characteristics are variable depending on processing, additives and finishing treatments, not to mention fabric construction.
Absorbency: Rayon is the most absorbent of all cellulose fibers, even more so than cotton and linen. Because of this, rayon absorbs perspiration and allows it to evaporate away from the skin, making it an excellent summer fabric. Its high absorbency applies equally to dyes, allowing beautiful, deep, rich colors.
Strength: It loses a great deal of strength when wet. Because of this, it stretches and shrinks more than cotton.
Abrasion resistance: Poor due to inelasticity of the fibers. It is easily damaged by scraping and will pill on the surface of the cloth.
Flammability: Because of its excessive flammability (see burning test), it inspired the Flammable Fabrics Act. The FFA was enacted by the U.S. Department of Commerce in 1953 in response to public concern over a number of serious burn accidents involving brushed rayon high pile sweaters (referred to as “torch sweaters”) and children’s cowboy chaps which could easily catch fire and flash burn.
Static: No static build-up.
Chemical reactions: Because it is a cellulose fiber, it is damaged by even relatively weak acids.

Fiber and Fabric Care

Rayon fabric should always be dry-cleaned, unless it has been specifically treated for washability. Even then, great care should be taken to guard against shrinkage.

End Uses

Rayon

Yarns: embroidery thread, chenille, cord, novelty yarns.
Fabrics: challis, crepe, gabardine, suitings, yarn-dyes, faille, gauze, prints, textured rayons & other novelties, outerwear fabrics, and linings for fur coats & outerwear.
Apparel: blouses, dresses, jackets, lingerie, linings, millinery (hats), slacks, sport shirts, sportswear, suits, ties, work clothes.
Domestic Textiles: bedspreads, blankets, curtains, draperies, sheets, slip covers, tablecloths, upholstery.
Industrial Textiles: high-tenacity rayon is used as reinforcement to mechanical rubber goods (tires, hoses), applications within the aerospace, agricultural and textile industries.

Viscose

Pulps: high-tenacity rayon cord (for tires, industrial belts, and hoses), textile fibers, sausage casing, cellophane.
Fabrics: lace, dress materials, dull crepe, satin, taffeta, brasso, velvet, georgette, and tapestry.
Apparel: dresses, saris.
Domestic Textiles: upholstery, curtain and finishing fabric.
Industrial Textiles: braided cord, tapes.

Lyocell

Pulps: premium textile fibers
Apparel: dresses, suits, sportswear, pants, jackets, blouses, skirts.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to understand, demonstrate the process of making long Rayon fibers from short cellulose fibers such as cotton linter. Specially I would like to know if we can use other cellulose based material such as wood or paper to make rayon fibers.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

The independent variable also known as manipulated variable is the source of cellulose fiber (cotton, paper, wood)

The dependent variable also known as responding variable is the resulting Rayon fiber. (Positive=fiber was successfully produced, Negative=No fiber was produced.)

Controlled variables are experiment procedures and material.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

I think any type of cellulose can be converted to Rayon.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

In this experiment 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. In order to make Rayon, you need to dissolve cotton in a solution and then recover it in the form of long fibers. In the following procedure, cellulose is actually dissolved in [Cu(NH3)4](OH)2 solution and then regenerated as rayon when extruded into sulfuric acid.

The primary reactions involved are:

NaOH(aq) + CuSO4(aq) —> Cu(OH)2(s) + Na2SO4(aq)
Cu(OH)2(aq) —> Cu2+(aq) + 2 OH-(aq)
n Cu2+(aq) + (cellulose)n + 2n OH- —> (CuC6H8O5)n + 2n H2O

Procedure:

Dissolve 25.0 g of CuSO4·5H2O in 100 mL distilled water. Heat the water to accelerate the dissolving process.
Dissolve 8.0 grams NaOH in 200 mL distilled water.
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.
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 Schweitzer’s reagent. Stopper the flask and stir periodically for 24 hours. Use a magnetic stirrer, if available.
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” should form.
The clumps or threads can be washed free of the solution to show the white color of the rayon.

Flush the ammonia solution and the sulfuric acid solution down the drain with copious amounts of water. Use the Rayon as a part of your display.

This experiment is using filter paper as a source of cellulose. Repeat this procedure with other sources of cellulose such as cotton and balsa wood or any other wood chips.

Materials and Equipment:

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 water)*
11.0 cm filter paper*

Equipment

250-mL Erlenmeyer flask
1000-mL beaker
syringe or bulb/pipette combination
funnel
filter paper
funnel support
magnetic stirrer (optional)
Buchner funnel and filtering flask (optional)

* Modifications/Substitutions:

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.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

No calculations are required for the final results; however the amounts or ratio of material described in the procedure are calculated based on the molecular weight of substances involved in each reaction.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Possible Errors:

Filtration of Cu(OH)2 can be a problem; small amounts of precipitate should be filtered and then combined in one container.
Samples of rayon and other synthetics could be shown and their properties discussed.

References:

Alyea, H.N., Dutton, F.B., “Tested Demonstrations in Chemistry, Journal of Chemical Education, Easton, PA, 1965, p. 14.
– Describes another preparation of rayon.

Summerlin, L.R. and Ealy, J.L., Jr., Chemical Demonstrations – A Sourcebook for Teachers, American Chemical Society, Washington, 1985, p. 126.
– This work describes another short prep of rayon.

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Make Synthetic Fiber Production of Cuprammonium Rayon.