1. PURPOSE This exercise examines some of the different plastics readily made in a laboratory setting and properties of some commercial plastics.

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1 CIP1 PLASTICS Last Revised: February PURPOSE This exercise examines some of the different plastics readily made in a laboratory setting and properties of some commercial plastics. 2. REAGENTS & EQUIPMENT 2.1 Methyl methacrylate 2.2 Lauroyl peroxide 2.3 Melamine 2.4 Methanal solution 2.5 1,2-Benzenedicarboxylic anhydride (phthalic anhydride) 2.6 1,2-Ethandiol (ethylene glycol) 2.7 1,2,3-Propantriol (glycerol) 2.8 Decandioyl dichloride (sebacoyl chloride) in trichloromethane (1 ml to 30 ml) 2.9 1,6-Hexandiamine in water (1.5g to 20mL) 2.10 Plastic samples 2.11 Melting point apparatus 2.12 Hexane 2.13 Saturated salt solution 2.14 Stopwatch/timer %w/v polyvinyl alcohol solution %w/v borax solution 3. PROCEDURE I. Synthesis A. Perspex (poly methyl methacrylate) 3.1 Combine methyl methacrylate (1 ml approx.) and lauroyl peroxide (a few crystals) in a test tube. Seal the end of the tube with a foil-coated stopper and heat in a waterbath for 90 minutes. 3.2 Cool in an icebath, which should allow the Perspex to separate from the test tube wall. If not, break tube carefully. B. Melamine resin 3.3 Place melamine (5.0g) in a boiling tube, add methanal (formaldehyde) (10mL), then heat in a boiling water bath in a fume hood. 3.4 Swirl the mixture every five minutes to check on its viscosity and to ensure thorough mixing of the reactants. 3.5 After approximately 45 minutes the mixture may be withdrawn from the water bath and heated in a 160C oven for 2 hours. 3.6 Remove the solidified product from the test tube (this may require breaking the tube) under teacher supervision.

2 C. Polyesters 3.7 Place 1,2-benzenedicarboxylic anhydride (phthalic anhydride) (3.0g) and sodium ethanoate (0.1g) into each of two test tubes. 3.8 Mark the tubes with an A and a B. 3.9 Into tube A place 1,2-ethandiol (ethylene glycol) (1.5mL) Into tube B place 1,2,3-propantriol (glycerol) (1.5mL) Heat both tubes in an oven at 160C for one hour Remove the tubes from the oven and allow to cool. D. Nylon 3.13 Pour the decandioyl dichloride (sebacoyl chloride) in trichloromethane solution (30 ml) into a small beaker Carefully pour the aqueous solution of 1,6-hexandiamine through a small funnel placed against the side of the beaker so that the aqueous layer sits on top of the trichloromethane layer and does not disturb it. A thin film of nylon polymer should form immediately at the interface between the two liquids Using a small metal hook attached to a glass rod, pull a small portion of the polymer up from the surface and wrap it around the rod. Continue to wind it around the rod until no more polymer is formed Remove the nylon from the rod (use gloves), and wash it with several portions 50% aqueous propanone, then several small portions of water Dry the product in an oven for a short period at 50C. E. Polyvinyl alcohol 3.18 Pour 100 ml of polyvinyl alcohol solution into a foam plastic cup Add 15 ml of 4% borax, stirring with a wooden stirrer Stir for 5 minutes, and observe what happens Leave for 30 minutes before testing. F. Testing Heat 3.22 Place a small piece (if possible) of the melamine, Perspex and nylon made in Part I (not Parts C & E) in a hot Bunsen flame and observe. Mechanical strength 3.23 Compare their viscosities of the two polyesters 3.24 Compare the strengths of the nylon and melamine by attempting to deform them (eg by hand or with a hammer) Lift the PVA plastic slowly out of the cup with the wooden stirrer and record your observations. CIP1 2

3 II. Properties of commercial plastics You will be assigned one commercial plastic sample in strip and pellet form from the following: polyethylene terephthalate (PET) high density polyethylene (HDPE) low density polyethylene (LDPE) polyvinyl chloride (PVC) polystyrene (PS) polypropylene (PP) You will carry out Tests A-D on your plastic. You will need to obtain results for all the plastics, which will be recorded on a common Results Sheet. Everyone will use the same plastic for Test E. A. Mechanical Strength 3.26 Bend a strip of your plastic with your hands. Record how easy it is to bend, and whether it stays bent, returns to the original shape or breaks. B. Solvent Penetration 3.27 In a small beaker (preferably 100 ml or less), pour hexane to a depth of 1 cm Place a piece of your plastic in the hexane and leave for 10 minutes Remove the plastic from the beaker and dry with paper towel Repeat the bending test. Is there any difference? C. Softening Point 3.31 Hold one strip of your plastic vertically, so that the narrow end is touching the melting point bench. Starting at the low temperature end, rest the strip on the bench for a few seconds. If when you lift the strip off, it doesn t stick, move it to a point 10ºC higher (use the pointer). Keep doing this until you reach the softening point. Once you reach this, remove the plastic from the bench as quickly as possible so that as little residue as possible remains. D. Density 3.32 Pour 1 cm of saturated salt solution into a test tube Drop in a pellet of your plastic and observe whether it sinks or floats. E. Moulding 3.34 Line a porcelain crucible with aluminium foil, and grease the exposed surface with Vaseline (or similar) Add ten pellets of low density polyethylene (LDPE) to the crucible, and place in a 150 C oven. Leave for 5 minutes or until the pellets have melted Remove the crucible from the oven, and allow to cool on a heat pad Once cool enough to hold, remove the foil from the crucible and sit it in an icebath until the plastic has completely solidified Remove the plastic bead from the foil and record your observations about its appearance (eg colour, transparency, hardness) Repeat steps with the bead. CIP1 3

4 4. REPORT Discussion Questions draw the structures of each monomer used in Parts I(a)-(d) draw a partial structure of each polymer in Parts I(a)-(d) identify each polymer as thermoplastic or thermoset identify each reaction in Part I as addition or condensation explain the difference in viscosities between the two polyesters in Part I(c) explain the mechanical strength difference between nylon and melamine explain what is happening to the PVA when it is mixed with borax (Hint - type polyvinyl alcohol into Google) compare the physical properties of each of the plastics tested in Part II, relating differences in chemical structure to the variations in properties compare the permeability of the plastic films, relating differences to differences in the plastic type and its intended use 1. The environmental consequences of plastics is an important issue. (a) Why don't most plastics degrade in landfill dumps? (b) Which plastics do you think could be recycled? (c) What problems are associated with the recycling of plastics? 2. Give two advantages and two disadvantages of the use of plastics in packaging. 3. Name three common types of additives present in plastics, and describe their purpose. 4. Give a commercial application of each type of plastic in Parts I & II of this exercise. 5. Explain why the permeability of plastic film is important in packaging of foods. 6. Polyvinyl alcohol is made from polyvinyl acetate. (a) What type of reaction is this? (b) Polyvinyl alcohol is only water-soluble if the reaction from the acetate is not complete, i.e. some of the CH 3 COO groups remain. Suggest a reason for this. CIP1 4

5 CIP1 COMMON RESULTS SHEET (PART II) PLASTICS PET LDPE HDPE PVC PP PS Ease of bending Bend/straighten/break Solvent effect Softening pt Density