TEXTILES NANO EXPERIMENT 1 MAKING AND INVESTIGATING CASEIN PLASTIC Experiment 1: Making and Investigating Casein Plastic Part A: Making Casein Plastic Introduction Casein is a phosphoprotein found in fresh milk. It is also used in the manufacture of adhesives, binders, protective coatings, plastics (e.g. knife handles and knitting needles), fabrics, food additives and many other products. Bodybuilders use powdered casein as a slow-digesting source of amino acids. Aim To make casein plastic. Materials  full cream milk  vinegar  Bunsen burner  heat-proof mat  tripod  gauze mat  100mL measuring cylinder  two 250mL beakers  thermometer  stirring rod  elastic band  coarse cloth for straining  paper towel  assorted moulds (bottle tops, chocolate trays)  fine sandpaper  tongs Method: 1. Place 100ml of milk in a 250mL beaker and heat gently to 50°C. Do not overheat. 1 Experiment 1: Making and Investigating Casein Plastic 2. Add 10mL vinegar and stir with a stirring rod. The milk should curdle forming white lumps of curds (casein) and a yellowish liquid called whey. 3. Place the coarse cloth in a funnel and strain the curds and whey into another beaker. 4. Squeeze the cloth to remove as much liquid as you can 5. Empty the curd onto paper towel and pat dry. 6. Press casein into a mould and leave to dry in the sun. 7. After 1 to 2 days, remove from mould and polish with sandpaper. Discussion: 1. Describe your casein plastic. 2. Casein is a protein. What is a protein? Are there any other proteins found in milk? 3. When the casein was allowed to dry it forms a polymer. What is a polymer? Give at least 5 examples of other polymers (2 must be biological molecules). 4. Research the toothpaste product ‘Recaldent’. How do Nanotechnologists use casein to create the active ingredient in this product? Part B: Investigating the Properties of Plastics Aim To test a variety of plastics and look at their properties. Introduction Plastics are made up of polymers, which are very large molecules made from repeating units called monomers. Chemists describe polymers according to their plastic properties. Polymers can be either thermoplastic or thermosetting polymers. Thermoplastic polymers are soft, stretchy and they soften and melt when heated. Thermosetting polymers are hard and rigid. They char when heated leaving a black carbon residue. Materials and Equipment  Labelled samples of plastics (casein - prepared in Part A, polythene, polystyrene, PVC, Perspex, nylon,  fireproof mat 2 Experiment 1: Making and Investigating Casein Plastic  scissors  turpentine  nail polish remover  dilute HCl  250mL beaker  Tongs  Bunsen burner in fume hood (teacher demonstration only). Method 1. Observe and record the results of the flame test carried out by your teacher. 2. Carry out each remaining test as demonstrated by your teacher Discussion 1. What is the difference between thermoplastic and thermosetting plastic? 2. Classify your plastics as thermoplastic or thermosetting polymers. 3. Do any plastics sink in water? What does this indicate about their density? 4. Why must the burning of plastics be done in the fume hood? What does PVC produce when burnt? Conclusion Briefly summarise Part A and Part B and write some concluding comments. 3 Experiment 1: Making and Investigating Casein Plastic Results: Casein Polythene Polystyren e PVC Perspex Nylon Appearance Transparent, translucent, opaque? Flexibility Bendable or stiff? Feel Does it feel waxy? Ease of scratching Fingernail or scissors? Ease of cutting Does it cut with scissors? Description of cut edges Smooth or jagged? Density Does it float in water + 2 drops detergent? Dissolvability Does it dissolve in turpentine, HCl, nail polish? Effect of flame Does it melt or char? 4 Experiment 1: Making and Investigating Casein Plastic 5