| Date | May 2017 | Marks available | 3 | Reference code | 17M.3.sl.TZ2.3 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
Polymer nanocomposites often have better structural performance than conventional materials. Lithographic etching and metal coordination are two methods of assembling these nanocomposites.
Nanoparticles anchor plasticizers in PVC so that they cannot escape from the polymer as easily.
State the two distinct phases of a composite.
Identify the methods of assembling nanocomposites by completing the table.
Explain how the structure of plasticizers enables them to soften PVC.
Suggest a reason why nanoparticles can better anchor plasticizers in the polymer.
Markscheme
reinforcing «phase»
«embedded in» matrix «phase»
[2 marks]
Award [2] for all 4, [1] for 2 or 3 correct.
[2 marks]
Any three of:
contain a polar group «which locks into the polymer»
a non-polar group «which weakens the forces between chains»
embedded between chains of polymers
«plasticizer molecules» fit between chains
«plasticizer molecules» prevent chains from forming crystalline regions
«plasticizer molecules» keeps strands/chains/molecules separated
«plasticizer molecules» increase space/volume between chains
weakens intermolecular/dipole-dipole/London/dispersion/instantaneous induced dipole-induced dipole/van der Waals/vdW forces
Do not accept “«plasticizer molecules» “lower density” or “softer”.
[3 marks]
more places «for plasticizers» to bond
OR
increased surface area
[1 mark]
