Question 20N.3.sl.TZ0.3
| Date | November 2020 | Marks available | [Maximum mark: 8] | Reference code | 20N.3.sl.TZ0.3 |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Explain, Outline, Suggest | Question number | 3 | Adapted from | N/A |
Outline the two distinct phases of this composite.
[2]
carbon fibre reinforcing phase ✔
«in a» matrix phase of epoxy ✔
Award [1 max] for “reinforcing phase «embedded» in a matrix”.
Approximately 1% of the candidates this session attempted this option so feedback on this section by question is not possible due to the minimal number of scripts available for marking. The students that did attempt this option did not perform very well with several of them leaving some questions unanswered.
Thermoplastic composites are increasingly replacing thermosets.
Suggest one advantage of thermoplastic polymers over thermosets.
[1]
can be recycled
OR
can be reformed when hot
OR
high impact/chemical/abrasion resistance ✔
Approximately 1% of the candidates this session attempted this option so feedback on this section by question is not possible due to the minimal number of scripts available for marking. The students that did attempt this option did not perform very well with several of them leaving some questions unanswered.
Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the addition of phthalate ester plasticizers.
[3]
Any three of:
plasticizers embed/fit between «polymer» chains ✔
keep polymer strands/chains/molecules separated/apart ✔
weaken intermolecular/London/dispersion/attractive/forces/instantaneous induced dipole-induced dipole/forces «between chains» ✔
prevent chains from packing closely/forming regular packing/structure ✔
Accept “van der Waals/vdW” for “London”.
Approximately 1% of the candidates this session attempted this option so feedback on this section by question is not possible due to the minimal number of scripts available for marking. The students that did attempt this option did not perform very well with several of them leaving some questions unanswered.
Explain why phthalates are replaced by other plasticizers in the production of plastics.
[2]
Any two of:
readily released into environment
OR
have weak intermolecular forces «rather than covalent bonds between chains» ✔
get into biological systems by ingestion/inhalation ✔
interrupt endocrine systems
OR
affect release of hormones
OR
effect development of male reproductive system ✔
considered carcinogenic
OR
can cause cellular damage ✔
can cause early puberty in females ✔
can cause thyroid effects ✔
can cause asthma ✔
Do not accept just “are a health concern”.
Approximately 1% of the candidates this session attempted this option so feedback on this section by question is not possible due to the minimal number of scripts available for marking. The students that did attempt this option did not perform very well with several of them leaving some questions unanswered.