Making Rayon Fiber

Materials: ★★★ Requires materials not commonly found in school laboratories
Difficulty: ★★★ Requires a more experienced teacher
Safety: ★★★ Only to be attempted with adequate safety procedures and trained staff

Categories: Materials, Polymers

Alternative titles: Artificial Silk from Cotton

Summary

Cotton fibers are dissolved in a copper-ammonia complex solution to form a viscous liquid (viscose). When extruded into sulfuric acid, the cellulose precipitates as fine rayon fibers, simulating industrial artificial silk production.

Procedure

Prepare basic copper carbonate by reacting copper sulfate with baking soda, or use ready-made material.
Place about 4 g of basic copper carbonate into a beaker.
Add approximately 40 mL of concentrated ammonia solution (25%), forming a deep blue copper-ammonia complex.
Filter or decant to remove undissolved residue.
Gradually add ~1 g of cotton wool to the blue solution, stirring until it dissolves into a viscous liquid (viscose).
Prepare a 1 M sulfuric acid solution in a separate beaker.
Fill a syringe with viscose and slowly inject it into the sulfuric acid.
Observe as fine rayon fibers form, initially blue, then turning colorless as the copper salts are removed by the acid.
Collect the fibers and examine their texture.

Links

Making Rayon Fiber - Artificial silk, chemical experiment - Thoisoi2 - Chemical Experiments!:

Schweitzer Reagent : Making Rayon DIY demo - vibzz lab:

Variations

Try different extrusion methods (needle size, pouring, or pipette).
Compare rayon fibers with natural silk or nylon fibers to discuss properties.

Safety Precautions

Perform in a fume hood or well-ventilated area due to ammonia vapors.
Wear chemical-resistant gloves, safety glasses, and a lab coat.
Ammonia solution is corrosive and releases harmful fumes.
Copper compounds are toxic; avoid ingestion or skin contact.
Sulfuric acid (1 M) is corrosive; handle with care and rinse spills immediately.
Dispose of copper-containing waste properly as hazardous chemical waste.

Questions to Consider

What role does the copper-ammonia complex play in dissolving cotton? (It forms Schweizer’s reagent, which can dissolve cellulose.)
Why does sulfuric acid cause fibers to reappear? (The acid breaks down the copper complex and precipitates cellulose as solid fibers.)
How does rayon compare to natural silk in strength and softness?
What are some advantages and disadvantages of artificial fibers compared to natural ones?