Polymers

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Addition Polymers

The double bonds in alkenes can break and then join together to make long chais called addition polymers.  ---> Individual small alkenes are called monomers.

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Addition polymers are made up of repeating units. Repeating units look alot like the monomer but the double bond has opened out.

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Condensation Polymers

-Involves 2 different types of monomer, each monomer has at least 2 functional groups. Each functional group reacts with a group on the other monomer to form a link, creating polymer chains. Water is lost each time there is a link --> why its called condensation polymerisation. Examples include: polyamides, polyesters and polypeptides.

Formation of polyamides                                                                                                                Reactions between dicarboxylic acids and diamines make polyamides. Carboxyl groups of dicarboxylic acids react with the amino groups of the diamine to form amide links

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Condensation Polymers continued...

Dicarboxylic acids and diamines have functional groups on either end, so they can form 2 amide links and long chains can form. Need to learn...

Nylon 6,6

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Kevlar

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Condensation Polymers continued...

Formation of Polyesters

Carboxyl groups of dicarboxylic acids can react with the hydroxyl groups of diols to form ester link.

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Polymers joined by ester links are called polyesters. Example: Terylene..

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Biodegradability of Polymers

Addition Polymers such as poly(ethene) (a polyalkene) and polystyrene are chemically inert (Very Unreactive). This is because the bonds between the repeating units are non-polar, So they are not susceptible to attack by a nucleophile.                                                                                                 Being chemically inert is an advantage when the polymers are being used, But the disadvantage is it makes them non-biodegradable (Bonds can't be hydrolysed and won't break down naturally)

Condensation Polymers such as PET (aswell as polyesters and polyamides) can be broken down by hydrolysis. Because the bonds between the repeating units are polar and therefore susceptiable to attack by a nucleophile such as water.                                                                                                 As the bonds in condensation polymers can be hydrolysed, these polymers are biodegradable, although it is a very slow process.

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Diposing Polymers

Options are.... burying, burning or sorting for resusing or recycling. Non are ideal all have advantages and disadvantages:

BURYING WASTE PLASTIC: Generally used when plastic is hard to seperate from other waste.       + : Relatively cheap and easy method of waste disposal.                                                                    -: Requires large areas of land, As waste decomposes methane is released, Can contaminate water supplies.                                                                                                                                 BURNING WASTE PLASTIC:                                                                                                      +: Heat from burning used to generate electricity                                                                                  -: Carful control needs to take place to reduce toxic gases, Waste gases still contribute to greenhouse effect RECYCLING:                                                                                                                                          +: Reduces amount of waste going into landfill, Saves raw materials, Cost is lower than starting from scratch, Produces less CO2 than burning plastic.                                                                                  -: Technically difficult to do, Collecting Sorting and Precessing plastic is more expensive than using a land fill or burning, Can remake the plastic you started with, Plastic can be easily contaminated                         

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