3.3.12 Polymers Flashcards
What are condensation polymers?
- Condesation polymers usually involve two different types of monomer, each with at least two functional groups. Each functional group reacts with a group on another monomer to form a link, creating polymer chains
- When a link is formed, a water molecule is lost - hense the name condensation polymerisation
Name three examples of condensation polymers
- Polyamides
- Polyesters
- Polypeptides (proteins)
Explain the reaction between dicarboxylic acids and diamines to make polyamides
The carboxyl group if dicarboxylic acids react with the amino group of diamines to form amide links. Dicarboxylic acids and diamines have a funtional group at each end of the molecule, so long chains can form
HOOC-R-COOH + H2N-R’-NH2 -> HOOC-RCONH-R’-NH2 + H2O
A water molecule is eliminated
CONH = amide link
Give the equation for the creation of Nylon 6,6
1,6-diaminohexane and hexandoic acid make Nylon 6,6
n H2N(CH2)6NH2 + n HOOC(CH2)4COOH -> -(-NH(CH2)6NHCO(CH2)4CO-)n- + 2nH2O
What uses does Nylon 6,6 have?
- Carpet
- Clothing
- Rope
- Airbags
- Parachutes
Give the equation for the creation of Kevlar
1,4-diaminobenzene + benzene-1,4-dicarboxylic acid -> Kevlar + H2O
n H2N(C6H4)NH2 + n HOOC(C6H4)COOH -> -(-NH(C6H4)HNCO(C6H4)CO-)n- + 2nH2O
Give the uses of Kevlar
- Bullet proof vests
- Boat construction
- Car tires
- Lightweight sports equipment
Explain how the reaction between dicarboxylic acids and diols to make polyesters
The carboxyl groups of dicarboxylic acids can react with the hydroxyl groups of diols to form ester links.
Polymers joined by esters are called polyesters.
HOOC-R-COOH + HO-R’-OH -> HOOC-R-COO-R’-OH + H2O
A water molecule is eliminated
Give the equation for the creation of Terylene (PET)
Benzene-1,4-dicarboxylic acid + ethane-1,2-diol -> Terylene (PET)
n HOOC(C6H4)COOH + n HOCH2CH2OH -> -(-OOC(C6H4)COOCH2CH2-)n- + 2nH2O
Give the uses of Terylene (PET)
- Plastic bottles
- Clothing
- Sheets
- Sails
By which process are condensation polymers broken down into their original polymers?
Hydrolysis - water molecules are added back to the polymer and the links are broken - e.g.
-(-CORCONHR’NH-)n- +2nH2O -> n HOOCRCOOH + n H2NR’NH2
How do you draw the monomers from a condesation polymer?
- Break the chain through the middle of the bond of the amide or ester link
- Add an OH or H to each end of the new molecule
- For a polyamide the monomers need to be a dicarboxylic acid and a diamine
- For a polyester the monomers need to be a dicarboxylic acid and a diol
Why are condensation polymers generally stronger and more rigid than addition polymers?
Condensation polymers are made up of chains containing polar bonds, e.g. C-N and C-O. So, aswell as VDW forces, there are permanant dipole-dipole forces and hydrogen bonds between the polymer chains.
Why are addition polymers useful but difficult to dispose of?
- Polyalkenes such as poly(ethene) and polystyrene are addition polymers. They are made up of non-polar carbon chains, which makes them unreactive and chemically inert
- This is advantageous whilst being used e.g. a polystyrene won’t react with coffee, however this does mean they are non-biodegradeable
Why are condensation polymers biodegradable, why is this still a problem?
Condensation polymers such as polyesters and polyamides do have polar bonds in thier chains, which makes them open to attack by nucleophile. This means they can be broken down by hydrolysis so these polymers are biodegradeable, however this is a very slow process
How may waste plastics be disposed of?
- Burying in landfill
- Burned to produce electricity
- Recycling
Explain advantages and disadvantages of plastics are disposed of by burying
- Land fill is used when the plastic is:
~ Difficult to separate from different waste
~ Not in sufficient quantities to make separation financially worthwhile
~ Too difficult technically to recycle - Landfill is a relatively cheap and easy method of waste disposal, but it requires land
- As waste decomposes it can release methane - a green house gas leaks from landfill sites and can also contaminate water supplies
- The amount of waste we generate is becoming more of a problem, so landfill use needs to be reduced
Explain the advantages and disadvantages of waste plastics being burned
- Waste plastics can be burned to produce electricity
- The process needs to be carefully controlled to reduce the release of toxic gases e.g. polymers containing chlorine e.g. PVC produce HCl when burned, this has to be removed - so waste gases from the combustion are passed through scrubbers which can neutralise gases such as HCl by reacting them with a base
- Waste gases such as CO2 will still contribute to the green house effect
Explain the process of recycling
Because many plastics are made from non-renewable oil-fractions, it makes sense to recycle plastics as much as possible. There’s more than one way to recycle plastics. After sorting there are different types:
* Some plastics (e.g. poly(propene)) can be melted and remoulded
* Some plastics can be cracked into monomers, and these can be used to make more plastics or other chemicals
Plastics are usually marked to make sorting easier e.g. 3 = PVC, 5 + poly(propene)
Give the advantages of recycling
- It reduces the amount of waste going into landfill
- It saves raw materials - which is important because oil is non-renewable
- The cost of recyling plastics is lower than making the plastics from scratch
- It produces less CO2 emissions than burning the plastic
Give the disadvantages of recyling plastics
- It is techinally difficult to recycle plastics
- Collecting and, sorting and processing the plastic is more expensive than burning/ landfill
- You often can’t remake the plastic that was recycled - another plastic is made
- The plastic can easily be contaminated during the recyling process
