demonstrations:making_rayon_fiber
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?