Polymers Flashcards
What are the two types of polymers?
addition and condensation
What molecules undergo addition polymerisation?
alkenes
What is special about addition polymerisation?
no waste products formed
How are addition polymers formed?
via a free radical mechanism
What is a common free radical initiator?
peroxide
Why are addition polymers chemically unreactive and why is this useful?
c-c bonds are non-polar, useful as they cannot be attacked by acids/alkali/oxidising agents
How would you represent the repeating unit of an addition polymer?
no brackets, but no double bonds, just the polymer structure without any brackets
How is the polymerisation of ethene represented?
…………………………..H H
n H2C=CH2 —-> -(-C–C-)- n
H H
Poly(ethene) use?
plastic bags
Poly(propene) use?
pipes
Poly(chloroethene) (PVC) use?
records
Poly(styrene) use?
packaging
Teflon use?
non-stick pans
What are the options for solving the problem of polymers in landfill, and their problems?
-use biodegradable polymers - expensive
-incinerate them (can also be used to recover energy) - produces greenhouse gases and toxic gases
-recycle polymers - expensive
What is the problem with recycling?
-various types of plastic have to be separated from each other prior to recycling which is expensive, and complete separation is essential
-energy costs with remelt
-costs with transport/collection/cleaning of plastic
What is condensation polymerisation?
where monomers with two functional groups join together to make a polymer and a waste product (usually water)
What are the two types of condensation polymers?
-polyamides
-polyesters
What are the two ways of making polyamides?
-diamine + dicarboxylic acid
-amino acids
What are the properties and uses of a polyamide?
-hydrogen bonds formed means that the chains can line up with each other
-the H bonded cross links between polyamide strands give it strength
-kevlar= used to make bullet-proof vests due to tough-sheet like structure
Why are polyamides biodegradable?
have polar carbonyl bonds so can undergo hydrolysis when boiled with NaOH
How are polyesters made?
condensation polymerisation of 2 different bifunctional monomers - dicarboxylic acid with a diol
What is a use of a polyester?
fibres for clothes/carpets, plastic bottles = strong and light
What type of bond do polyesters contain?
ester bond C=O - O
When polyesters are hydrolysed, we make the
component monomers
Discuss the component monomers when hydrolysing polyesters in different conditions
acid hydrolysis - makes the component monomers directly
Why are polyesters able to be hydrolysed?
-they have polar carbonyl bonds
-when heated with NaOH solution, the OH- nucleophile will attack the electron deficient carbon atom
