| Date | November 2020 | Marks available | 3 | Reference code | 20N.3.sl.TZ0.3 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
| Carbon fibre reinforced plastic (CFRP) is a useful composite. Epoxy is a thermoset polymer that is used as a binding polymer when making CFRP. |
Outline the two distinct phases of this composite.
Thermoplastic composites are increasingly replacing thermosets.
Suggest one advantage of thermoplastic polymers over thermosets.
Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the addition of phthalate ester plasticizers.
Explain why phthalates are replaced by other plasticizers in the production of plastics.
Markscheme
carbon fibre reinforcing phase ✔
«in a» matrix phase of epoxy ✔
Award [1 max] for “reinforcing phase «embedded» in a matrix”.
can be recycled
OR
can be reformed when hot
OR
high impact/chemical/abrasion resistance ✔
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”.
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”.
Examiners report
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.
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.
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.
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.
Syllabus sections
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17M.3.hl.TZ2.3c:
Estimate the atom economy of this first step.
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17M.3.sl.TZ1.10b.ii:
Explain why the difference in their structures affects their melting points.
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17M.3.sl.TZ2.3c.i:
Explain how the structure of plasticizers enables them to soften PVC.
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19M.3.sl.TZ2.5d:
Explain how plasticizers affect the properties of plastics.
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18M.3.sl.TZ1.4a:
Both of these are thermoplastic polymers. Outline what this term means.
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19M.3.hl.TZ2.5a:
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
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19M.3.sl.TZ2.5a:
Draw a section of isotactic polychloroethene (polyvinylchloride, PVC) showing all the atoms and all the bonds of four monomer units.
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19M.3.hl.TZ1.4b:
Suggest, giving a reason, how elastomers used for the tyre tread can increase the traction between the tyre and the road.
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17M.3.sl.TZ1.10a:
Below are the IR spectra of two plastics (A and B); one is PETE, the other is low density polyethene (LDPE).
Deduce, giving your reasons, the identity and resin identification code (RIC) of A and B using sections 26 and 30 of the data booklet.
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16N.3.sl.TZ0.6a:
(i) Draw the structure of 2-methylpropene.
(ii) Deduce the repeating unit of poly(2-methylpropene).
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16N.3.sl.TZ0.6b:
Deduce the percentage atom economy for polymerization of 2-methylpropene.
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17M.3.sl.TZ2.3c.ii:
Suggest a reason why nanoparticles can better anchor plasticizers in the polymer.
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17N.3.sl.TZ0.7b.i:
Describe how the structures of LDPE and HDPE affect one mechanical property of the plastics.
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18M.3.hl.TZ1.4c.ii:
Deduce, giving a reason, whether the atom economy of a condensation polymerization, such as this, would be greater or less than an addition polymerization, such as the formation of HDPE.
- 19N.3.hl.TZ0.5b: State and explain why plasticizers are added to polymers.
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18N.3.sl.TZ0.2b.i:
Structures of poly(methyl acrylate), PMA, and Bakelite® are shown.
Suggest, giving reasons, which is the thermoplastic polymer and which is the thermosetting polymer.
-
19N.3.sl.TZ0.4a:
Draw a section of an isotactic polypropene polymer chain containing four repeating units.
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18M.3.sl.TZ1.4b.ii:
State one way in which a physical property of HDPE, other than density, differs from that of LDPE as a result of this structural difference.
-
18M.3.sl.TZ2.4a:
Sketch four repeating units of the polymer to show atactic and isotactic polypropene.
-
17M.3.sl.TZ1.10b.i:
Describe the difference in their structures.
- 19N.3.sl.TZ0.4b: Predict, with a reason, whether isotactic or atactic polypropene has the higher melting point.
- 19N.3.sl.TZ0.4c: Polypropene is a thermoplastic. Outline what is meant by thermoplastic.
- 19N.3.sl.TZ0.4d: Discuss why the recycling of plastics is an energy intensive process.
- 20N.3.sl.TZ0.3b(i): Thermoplastic composites are increasingly replacing thermosets. Suggest one advantage of...
-
19M.3.hl.TZ2.5c:
Explain how plasticizers affect the properties of plastics.
-
16N.3.sl.TZ0.6c:
(i) Suggest why incomplete combustion of plastic, such as polyvinyl chloride, is common in industrial and house fires.
(ii) Phthalate plasticizers such as DEHP, shown below, are frequently used in polyvinyl chloride.
With reference to bonding, suggest a reason why many adults have measurable levels of phthalates in their bodies.
-
19M.3.sl.TZ1.4b:
Suggest, giving a reason, how elastomers used for the tyre tread can increase the traction between the tyre and the road.
-
18N.3.hl.TZ0.2b:
Structures of poly(methyl acrylate), PMA, and Bakelite® are shown.
Suggest, giving reasons, which is the thermoplastic polymer and which is the thermosetting polymer.
-
18M.3.sl.TZ1.4b.i:
Compare and contrast the structures of HDPE and LDPE.
- 20N.3.sl.TZ0.3c: Explain why phthalates are replaced by other plasticizers in the production of plastics.
- 20N.3.hl.TZ0.3b(iii): Explain why phthalates are replaced by other plasticizers in the production of plastics.
- 20N.3.hl.TZ0.3b(i): Thermoplastic composites are increasingly replacing thermosets. Suggest one advantage of...
- 20N.3.hl.TZ0.3b(ii): Explain how thermoplastics, such as polyvinylchloride, PVC, can be made more flexible by the...
