Learning Aims:

Plasticizers are added to plastics such as PVC to make them more flexible and durable. They are often based on esters of polycarboxylic acids with linear or branched aliphatic alcohols of moderate chain length. Plasticizers embed themselves between the chains of polymers, spacing them apart. For plastics such as PVC, the more plasticiser added the more flexible it will be although its strength and hardness will decrease as a result of it.

In this activity, the plasticizer is removed from the PVC, leaving an inflexible glob of PVC.

  • PVC cling film (or PVC with plasticiser produced in activity 2)
  • Diethyl ether
  • Hot water
  • 250 cm3 conical flask
  • 250 cm3 beaker(s)
  • Graduated cylinder
  • Hot plate
  • Spatula
  • Balance
Suggestions for use:
  • Weigh out approximately 1 g of PVC cling film/plastic
  • Measure out 75 cm3 of diethyl ether into a 250 cm3 conical flask
  • Warm up the flask for 5-10 minutes in a water bath at 50°C in a fume cupboard. If a hot plate is not available then an unheated beaker of hot water can be used instead as diethyl ether boils at 35°C
  • Decant the diethyl ether from the conical flask into a 250 cm3 waste beaker. Add fresh ether and repeat the process
  • Remove the cling film/plastic from the beaker using a spatula after it has undergone two runs of diethyl ether and allow it to dry off in a fume cupboard
  • Weigh the cling film/plastic again and note the difference. Calculate the percentage weight loss (which should be over 20%)
  • To collect the sample of the plasticiser, distill off the ether in the waste beaker and you will obtain a viscous oil
Possible questions:
  • Compare and contrast the appearance and texture of the plastic before and after the experiment.
  • On a molecular level, what occurred to the polymer chains on removal of the plasticiser?
  • Design an experiment whereby you could test the size of pores in polymers using a plastic containing plasticiser and one without.