Polymers (Year 12)

Question 1

Ethene is a starting material for …

Answer 1

PAINT/DEGREASER:
- ClH2CH2Cl
- 1,2-dichloroethane

ANTIFREEZE:
- HOCH2CH2OH
- ethane-1,2-diol

POLYMERS:
- e.g polythene

VINEGAR:
- 5% CH3COOH
- ethanoic acid

Question 2

The manufacture of margarine

Answer 2

Process ~ Hardening

HYDROGENATION requirements :
- Hydrogen
- 150 degrees
- nickel catalyst

Type of reaction ~ ADDITION

• Oil partially solidifies and hardens
• vary the HARDNESS by adding different numbers of H2 molecules.

Fewer hydrogens ~ MORE SPREADABLE
More hydrogens ~ LESS SPREADABLE

Question 3

Making POLYMERS & TYPE of reaction

Answer 3

• Two ALKENE molecules COLLIDE and their PI-BOND BREAKS.
• Each carbon atom now has an UNPAIRED electron so is a RADICAL.
• C-C bond forms between two CARBON RADICALS.
• The END carbon atoms still have an unpaired electron so more MONOMERS can add on one at a time.

Type of reaction :
ADDITION POLYMERISATION

Question 4

Making Poly(ethene) in industry
Method 1 : RADICAL POLYMERISATION

Answer 4

Conditions:
- 200 degrees
- high pressure

Problem:
- get BRANCHED poly(ethene)

• FEWER CONTACT POINTS occur due to branches.
• WEAKER London forces
• FEWER atoms per unit volume
• Relatively LOW DENSITY

NAME ~ low density poly(ethene) or LDPE
USE ~ carrier bags due to its relatively low strength.

Question 5

Making poly(ethene) in industry
Method 2 : Ziegler-Natta Process

Answer 5

Conditions:
- 60 degrees
- TiCl3 & Al(C2H5)2Cl catalysts

Result:
- UNBRANCHED poly(ethene)

• GREATER CONTACT POINTS due to unbranched chains.
• STRONGER London forces
• MORE atoms per unit volume
• Relatively HIGH DENSITY

NAME ~ high density poly(ethene) or HDPE
USE ~ plastic food containers and bottles due to its relatively high strength.

Question 6

Why are polymers useful?

Answer 6

• Cheap
• Readily available
• Unreactive
• Durable

Question 7

Problem with polymers?

Answer 7

• Non-biodegradable
• Produce toxic fumes when incinerated

Question 8

Polymer Disposal:
- 85%
- 8%

Answer 8

• 85% is put in LANDFILL
• 5% is INCINERATED
  Problems:
• some plastics do not melt
• poisonous fumes can be produced
• plastics contain a large amount of CARBON which results in the greenhouse gas CO2 to be released

Question 9

Polymer Disposal:
- 7%

Answer 9

SORTING & RECYCLING:
- Conserves finite fossil fuels
- reduces landfill waste

DIFFICULTIES:
- Labour intensive

• colourants, stabilisers and plasticisers in plastic waste can release poisonous heavy metal ions.
• POISONOUS DIOXINS can be released if PVC & HDPE are not separated , thus spoiling the recycling process.

DEVELOPMENTS:
- New optical scanning techniques can separate PET from HDPE.

Question 10

RECLAMATION of polymers

Answer 10

• Processing of polymers into NEW PRODUCTS when they have been sorted.
• Chopped into small flakes, washed, melted and re-moulded.
• PET bottles ~ carpets, clothing & new bottles.
• HDPE ~ plastic boxes & bins

Question 11

Uses of polymers: Fuel source for energy

Answer 11

FUEL SOURCE FOR ENERGY:

• Have a high stored energy content
• Can incinerate non-recyclable polymers to produce HEAT ENERGY.
• Use the heat energy to produce STEAM , which drives TURBINES to make ELECTRICITY.

Question 12

Uses of polymers : Feedstock recycling

Answer 12

FEEDSTOCK RECYCLING:

• Chemical and thermal processes RECLAIM monomers, gases and oil from waste polymers.
• The polymers DO NOT have to be washed or sorted prior to the process.
• The RAW MATERIALS obtained produce NEW polymers.

Question 13

Uses of polymers : Recycling of PVC (polyvinyl chloride)

Answer 13

DIFFICULTIES:
- high chlorine content
- toxic acidic HCl gas & toxic dioxins are released during incineration.

DEVELOPMENTS:
- PVC on electrical wiring can be SEPARATED from other polymers using SOLVENTS and then re-used.

Question 14

Uses of polymers : Bioplastics

Answer 14

BIOPLASTICS:

Made from RENEWABLE resources such as:
- plant starch
- plant cellulose
- plant oil
- plant proteins

BENEFITS:
- biodegradable
- sustainable alternative to oil-based
polymers.
- Conserve crude oil reserves.

Question 15

Uses of polymers: Biodegradable & Compostable polymers

Answer 15

BIODEGRADABLE are made from either:
- starch
- cellulose
- additives which alter the structure

These allow them to be BROKEN DOWN by MICROORGANISMS and environmental conditions into:
- Water
- Carbon dioxide
- Inorganic compounds
- Biomass

COMPOSTABLE:
- Degrade to give NO TOXIC or VISIBLE
residues.

Question 16

Uses of polymers : Photodegradable polymers

Answer 16

Used when plant-based polymers cannot be used.

CARBONYL GROUPS (C=O):
- Carbonyl groups are incorporated into the backbone of the polymer.
- They absorb LIGHT ENERGY causing the polymer to break down.

                   ALTERNATIVELY

LIGHT SENSITIVE ADDITIVES:
- These are blended with the polymer and CATALYSE the break down of the polymer in the presence of UV light.

Photodegradable polymers in LANDFILLS are unlikely to receive sufficient EXPOSURE to light for degradation to occur.

Question 17

Uses of polymers : Cracking

Answer 17

This process produces:

• SHORTER chain ALKANES used as FUELS
• ALKENES which make POLYMERS

Question 18

Reagents & conditions when a polymer forms an alkene/alkane

Answer 18

• Zeolite catalyst
• 450 degrees