Polymers Flashcards
Ethene is a starting material for …
PAINT/DEGREASER:
- ClH2CH2Cl
- 1,2-dichloroethane
ANTIFREEZE:
- HOCH2CH2OH
- ethane-1,2-diol
POLYMERS:
- e.g polythene
VINEGAR:
- 5% CH3COOH
- ethanoic acid
The manufacture of margarine
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
Making POLYMERS & TYPE of reaction
- 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
Making Poly(ethene) in industry
Method 1 : RADICAL POLYMERISATION
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.
Making poly(ethene) in industry
Method 2 : Ziegler-Natta Process
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.
Why are polymers useful?
- Cheap
- Readily available
- Unreactive
- Durable
Problem with polymers?
- Non-biodegradable
- Produce toxic fumes when incinerated
Polymer Disposal:
- 85%
- 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
Polymer Disposal:
- 7%
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.
RECLAMATION of polymers
- 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
Uses of polymers: Fuel source for energy
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.
Uses of polymers : Feedstock recycling
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.
Uses of polymers : Recycling of PVC
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.
Uses of polymers : Bioplastics
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.
Uses of polymers: Biodegradable & Compostable polymers
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.
