Polymers

Question 1

thermoplastics vs thermosetting structure

Answer 1

structure:
- thermoplastics: weak interactions between polymer chains
- thermosetting: strong cross-link between polymer chains - strong heating will result in the breaking of all covalent bonds in the polymer chains, not just the cross-links, causing it to degrade instead of melt

Question 2

thermoplastics vs thermosetting properties

Answer 2

thermoplastics:
- hard/rigid at room temperature but soft when heated, can be melted

thermosetting:
- very hard/rigid/brittle
- cannot be melted
-degrade upon heat

Question 3

thermoplastics vs thermosetting bonding

Answer 3

thermoplastics:
- extensive intermolecular forces of attraction between chains so it is hard at room temperature
- chains are not cross-linked
- heating provides energy to overcome the weaker forces of attraction between the individual polymer chains, causing them to slide past each other, and the material melts/soften

thermosetting:
- polymer chains are cross-linked and this network of strong covalent bonds holds the layers together so it is hard
- cross-links also prohibit chain movement so it is brittle
- heating does not break these cross-links

Question 4

thermoplastics vs thermosetting solubility

Answer 4

thermoplastics:
- can be dissolved using suitable solvents

thermosetting:
- cannot be dissolved using suitable solvents

Question 5

thermoplastics vs thermosetting recycling

Answer 5

thermoplastics can be recycled, but thermosetting cannot

Question 6

LDPE and HDPE

Answer 6

Low-density poly(ethene)
- lower density
- lower melting point
- strong and hard/rigid
- consists of long carbon chains with many branches along the chain
- do not pack well due to branching
- resulting in weaker id-id interactions
- plastics bags and cling films

High-density poly(ethene)
- consists of long chains joined together in a linear fashion
- linear chains pack well
- resulting in stronger id-id interactions
- used in plastic milk bottles and bone substitutes in surgery

Question 7

PVA vs PVC

Answer 7

Poly(vinyl alcohol):
- water-soluble
- due to -OH group which can form hydrogen bonds with water molecules

Poly(vinyl chloride):
- water-resistant
- no -OH group to form hydrogen bonds with water molecules

Question 8

PP vs PET

Answer 8

Poly(propene):
- Polymer contains non-polar and strong C-C bonds which are resistant to acidic/alkaline hydrolysis
- no ester bonds to undergo hydrolysis

Poly(ethylene terephthalate):
- ester groups in the polymer chain. undergoes acidic hydrolysis to form carboxylic acids and alcohols
- ester groups in the polymer chain undergoes alkaline hydrolysis to form carboxylate salts and alcohols
- causing this polymer chain to break down
- ester group undergoes hydrolysis
- cannot be used to store strongly alkaline solutions

Question 9

Graphene

Answer 9

way to synthesise graphene:
- overcome the id-id interactions between the hexagonal layers in graphite

properties of graphene:
- extremely high surface to volume ratio
- high tensile strength as each carbon atom is attached to 3 others by a network of strong covalent bonds within the graphene layer
-excellent electrical conductor as one p electron per carbon atom delocalised over the whole graphene layer