F324: Module 2: Polymerisation

Question 1

C) What is bakelite made from?
What type of polymer is it?
What are its uses?

Answer 1

• Made from the condensation reaction of formaldehyde (methanal) with phenol
• It is a thermosetting polymer- it cannot be melted once it has been formed
• It was originally used for making electrical sockets and plugs

Question 2

C) What is the difference between thermosetting and thermoplastic?

Answer 2

• Thermosetting- cannot be melted after it has been formed

- Thermoplastic- can be melted after it has been formed (better in recycling)

Question 3

C) Describe the two types of polymerisation and give examples of each

Answer 3

• Addition polymerisation- where alkenes undergo addition with themselves. The double bond breaks and two molecules are added either side (continuing on)… An example of this is PVC where the monomer is H2C=CHCl
• Condensation polymerisation - Where two molecules join together to form either polyesters or polyamides with the elimination of a smaller molecule.

Question 4

C) Describe the reaction and conditions for the formation of Terylene
What are the properties of this polymer?

Answer 4

• Made in a condensation polymerisation reaction where Ethane-1,2-diol is polymerised with Benzene-1,4-dicarboxylic acid
• Antimony (III) oxide catalyst
• 280 degrees Celsius
• Rigid due to the 1, 4 links across the benzene ring, producing a more linear polymer. This enables the chains to pack more closely together which produces strong intermolecular forces and so can be spun into strong threads in the clothing industry

Question 5

C) Describe the reaction and conditions for the formation of polylactic acid
What are the properties of this polymer?

Answer 5

• Lactic acid is made from bacterial fermentation of sugar from the corn starch. This then dimerises to lactide which then forms poly lactic acid through polymerisation.
• Its biodegradable and environmentally friendly as the starting material comes from corn starch instead of crude oil.

(the name for lactic acid is 2-hydroxypropanoic acid)

Question 6

C) How is nylon 66 formed?

Answer 6

1,6-diaminohexane polymerises with hexanedioic acid to form a polymer with amide links

Question 7

I) What are the requirements for the monomer in a condensation reaction?

Answer 7

The monomers making up the polymer must have 2 functional groups which can be identical or different.

Question 8

I) What makes nylon fibres elastic?

Answer 8

The long chains of polyamides in nylon fibres are held together by hydrogen bonds. These hydrogen bonds can be easily broken and reformed, making nylon fibres elastic.

Question 9

I) Why is kevlar so strong (used in bullet proof vests)?

Answer 9

The perfect alignment of the chains and multiple hydrogen bonding makes kevlar incredibly strong.

Question 10

I) How would you determine the repeat unit for a polymer?

Answer 10

Draw a bracket line where a distinctive group (e.g. carbonyl, amine etc) begins or ends.

Follow the chain until you come to just before this group is about to repeat itself and draw another bracket.

Question 11

I) How would you determine the monomer units of a polymer?

Answer 11

Determine what linkage is in the polymer (e.g. -C=ONH-).

Determine what the two monomer units are on either side of the linkage

e.g. to make an amide like you need a diamine and dicarboxylic acid.

Similarly is the polymer is a polyester, then the monomers are probably a Diol and a dicarboxylic acid (with the exception of PLA).

Question 12

I) What are the main problems with polymers?

Answer 12

Many polymers are not biodegradable and therefore persist in the environment, becoming a litter problem and a danger to wildlife.

Disposal of polymers by burning is problematic because toxic fumes are produced unless very high temperatures are used.

Question 13

I) Describe the 3 main ways that environmental waste due to polymers can be minimised.

Answer 13

The C = O Bond absorbs radiation. Incorporating these bonds into the polymer chain will mean that, when radiation is absorbed by the bond, the large amount of energy absorbed caused the chain to breakdown
(Photodegradability).

Ester and Amide bonds can be hydrolysed by acids and alkalis, thus helping their breakdown and disposal.

Producing polymers formed from plant feedstock such as corn starch, wheat and sugar beet which are all naturally biodegradable.

Question 14

I) What are the advantages and disadvantages to using polymers based on starch?

Answer 14

Advantages:

• They are biodegradable.
• The are carbon neutral.
• Litter degrade more quickly reducing the litter problem.
• They are formed from renewable resources so don’t use fossil fuels.

Disadvantages:

• Land used for growing corn starch is not used for growing food.
• The shelf-life of packaging is reduced.
• If mixed with other plastics for recycling, their value is reduced.
• The have poorer mechanical strength than plastics based on fossil fuels.