Addition Polymers 

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  • Created by: lollocket
  • Created on: 01-03-16 19:56
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  • Addition Polymers (Polyalkenes)
    • Reactivity
      • Very unreactive as they have a long chain of saturated alkane molecules.
      • The carbon-carbon bonds and carbon-hydrogen bonds are very strong covelent bonds which require lots of energy to break. This makes them unreactive.
    • Properties
      • The hydrocarbon chains are very long with strong Van Der Waals Forces (London Forces) between the molecules.
        • Relatively  high melting and boiling points.
        • There are also variable chains and chain lenghts which means the are various Van Der Waals forces which results in different strengths.
        • The chains aren't rigidly held together which makes the polymers soft.
        • The chains are non-polar and have strong intermolecular forces which results in the chains becoming tangled. Due to this the polymers are insoluble in water and non-polar solvents.
    • Biodegradable
      • Low reactivity results in the polyalkenes not being easily decomposed by nature, which results in a long life time. This results in them being non-biodegradable
      • They cause environmental hazards as they are persistent in nature and difficult to dispose of.
      • They are not attacked by biological agents, such as enzymes, as they can't be broken down easily.
      • Reactivity
        • Very unreactive as they have a long chain of saturated alkane molecules.
        • The carbon-carbon bonds and carbon-hydrogen bonds are very strong covelent bonds which require lots of energy to break. This makes them unreactive.
    • Modification
      • Easily modified by adding additives such as plasticisers  making them suitable for a variety of uses.
      • Plasticisers are small molecules that get within the polymer chains, forcing them apart which allows them to slide across each other easily. This makes the polymer more flexible.
      • An example would be poly(chloroethene) (PVC/Vinyl) as it can be rigid for drain pipes and flexible for plastic aprons.
    • Density
      • Low
        • Polythene is produced by polymerising ethene at high temperatures through free radical mechanism. A polymer with a certain amount of chain branching formed.
        • The branched chains don't pack closely together which means the product is quite flexiable and stretches well.
        • Suitable for plastic bags, sheeting and insulation for electrical cables.
      • High
        • Polythene is made at tempuratures and prssures a little over room conditions using a Ziegler - Natta catalyst.
        • The polymer has less chain branching so chains can pack together well. This makes The density of plastic greater and the melting point higher.
        • Some uses are milk crates, buckets and bottles as low density would not be rigid enough.
    • Recycling
      • Mechanical
        • Different types f plastic are separated, then washed and sorted. They could then be ground down into small pellets making it easier to melt and remould.
      • Feedstock
        • The plastics are broken down by heating them to a certain temperature. This is done by the polymers breaking there bonds to form monomers. These monomers are then used to produce new plastics.

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