Activity 3.8 - Identification of polymers

• On the basis of previous results the students will create a material, which will allow them the identification of the unknown sample of polymeric substance.

Gas burner, toluene, chloroform, water, formic acid, sulphuric acid, petrol, ethanol, cyclohexane, phenol, hob or cooker, paper or white plate, two beakers of 100-150 ml, needle, and thermocouple

Samples of plastics (PE – polyethylene, PP - polypropylene, PS - polystyrene, PVAc – polyvinyl acetate, PMMA – polymethylmethacrylate, PC – polycarbonate, PA – polyamide, PUR – polyurethane, PET – polyethylene terephthalate, PVC – polyvinylchloride, PTFE – polytetrafluoroethylene, MF – aminoplastics)

Identification of polymer:

Within the previous activity, due to a number of experiments, you have revealed certain physical and chemical properties of some polymers. You have found out that these properties are quite varied. Try to identify the type of polymer in the unknown sample. However, prior to this, determine the strategy of how to identify the polymer in the sample and justify the individual steps. Based on this determination, work out a protocol in the form of a record containing the following parts:

a) Title of protocol: What is the subject of your work (e.g. Identification of unknown sample of polymer)

b) Procedure of test: in essence, a proposed strategy of identification procedure and its justification

c) Results of tests: results of the individual tests, i.e. how the sample responded to the individual tests (e.g. into which category it belong as for its density, how it reacts in the flame – type of smoke, colouration of flame, …)

d) Discussion: What type of polymer it is and why – justification of your choice

e) Conclusion: Unambiguous conclusion about which polymer it is (e.g. the studied sample of polymer is polypropylene.

The students determine the type of polymer in the sample supplied by the teacher; however they should first determine an appropriate strategy to make the determination efficient. For this, they will use the results from the previous activity. Experiments should not therefore be experimentally demanding. An appropriate procedure can be e.g. first a performance of less selective but simple classification of polymers (e.g. classification of polymers based on their density), followed by more selective tests (hardness, solubility test and tests in the flame – colouration of the flame, smoke, charred residue, etc.). The last test can be the appearance test. Obviously there are also many other appropriate procedures; it is important for the students not to proceed randomly but they should plan and justify their procedure.