Unit 2Polymers

HIGHER CHEMISTRY REVISION.

Unit 2:- Polymers

1. Concorde aircraft were grounded after an incident in which the fuel tank in one of the aeroplanes was punctured by a piece of metal. As a result the fuel tanks are now coated with the polymer, Kevlar.

(a) What property of Kevlar makes it suitable for this use?  

(b) The repeating unit in Kevlar is shown below.

 

 

 

 

What is the name given to the outlined group in this

repeating unit?

O

- C – N

H

(a) Kevlar is very strong and lightweight.

(b) Amide group or amide link.

2. Urea-methanal is a polymer which can be made using coal as a feedstock.

The flow diagram shows the steps involved in the production of the polymer.

Coal

(mainly carbon)

  Step 1

Carbon monoxide + hydrogen

Step 2

methanol

Step 3

methanal

Step 4

Urea-methanal polymer

(a) Name the mixture of gases produced in step 1.

(b) Name the type of reaction taking place in step 3.

(c) (i) In step 4 methanol reacts with urea, H2NCONH2.

Draw the full structural formula for urea.

(ii) The urea-methanal polymer does not soften on heating.

What name is given to this type of plastic?

(a) Synthesis gas.

(b) Oxidation.

(c) (i) H O H

N – C - N

H H

(ii) Thermosetting

polymer

3. Acrylonitrile, CH2CHCN, is the monomer used in the manufacture of Acrilan.

(a) (i) Draw the full structural formula for acrylonitrile.

(ii) Name the type of polymerisation which occurs in the manufacture of Acrilan.

(a) Acrylonitrile can be reduced in neutral aqueous solution forming (CH2CH2CN) 2.

Hydroxide ions are also produced in the reaction.

Complete and balance the ion-electron equation for the reduction reaction described above.

CH2CHCN (CH2CH2CN) 2 + OH-

4. Vinyl acetate is the monomer for the preparation of polyvinylacetate (PVA) which

is widely used in the building industry.

Vinyl acetate has the structural formula.

O

CH3—C—O—CH = CH2

(a) Draw part of the structure of polyvinylacetate, showing three monomer units

joined together.

b) Vinyl acetate and hexane have the same relative formula mass.

Explain why you would expect vinyl acetate to have a higher boiling point than

hexane.

(a) (i) H H

C = C

H C N

(ii) Addition polymerisation.

(b) 2CH2CHCN + 2H2O +2e- (CH2CH2CN) 2 + 2OH-

(a)

H H H H H H

C – C – C – C – C - C

O H O H O H

C=O C=O C=O

CH3 CH3 CH3

(b) The C=O bond in vinyl acetate is polar

as oxygen is more electronegative than

carbon. Polar attractions between the

molecules are stronger than the van der

Waals forces between the non-polar

hexane molecules.

5. (a) Kevlar and Nomex are examples of recently manufactured polymers. Their propertie are different

because they are made from different monomers.

The diamine monomer used to make Nomex is 1,3-diaminobenzene.

1,3-diaminobenzene

This reacts with the other monomer to form the repeating unit shown.

(i) Draw the structural formula for the other monomer.

(ii) The repeating unit in Kevlar is:

Name the diamine used to make Kevlar.

(b) Another recently manufactured polymer is polyvinylcarbazole.

Give an unusual property of polyvinylcarbazole which makes it suitable for use in photocopiers.

N

H

H

N H

H

N

H

H

N H

H

N

H

H

N

H

C O

C

O

OH

N

H

H

N

H

C O

C

O

OH

N

H

H

N H

C

O

N

H

H

N

H

H

N H

C

O

N

H

H

(a) (i)

(ii) 1,4-diaminobenzene.

(b) Photoconductive – it becomes

an electrica conductor when

exposed to light.

O

H

C O

C

O

O

H

O

H

C O

C

O

O

H