What is addition polymerisation?
-lots of alkenes opened up at the double bond and joined together to form polymer chains
What are polymers?
-formed when lots of monomers join together
What are the conditions needed for addition polymerisation?
- high pressure
- catalyst
What do weak forces mean about a plastic?
- chains are free to slide over each other
- plastic can be stretched easily and has a low melting point
What do strong forces mean about a plastic?
- stronger bonds, possibly covalent bonds between chains
- or cross-linking bridges
- high melting point
- plastics are rigid and can’t be stretched as the crosslinks hold the chains firmly together
What are some types of polymers?
- strong, rigid (e.g.high density polyethene) used to make plastic milk bottles
- light, stretchable (e.g.low density polyethene) used for shopping bags and squeezy bottles.Low melting point, so no good to carry very hot things
- PVC is strong and durable, can be made either rigid or stretchy. Rigid used for window frames and piping, stretchy used to make synthetic leather
- polystyrene foam used in packaging to protect breakable things, disposable coffee cups (thermal insulator, trapped air)
How is gore-tex made?
-laminating a thin film of expanded PTFE onto a layer of another fabric, e.g. nylon or polyester. Making PTFE sturdier
What are the advantages of gore-tex?
- PTFE film has tiny holes which let water vapour through, so it is breathable
- holes not big enough to let water droplets through and PTFE repels liquid water, so waterproof
- great for outdoorsy types
What are the disadvantages of nylon?
-polyurethane coating doesn’t let water vapour pass through so sweat condenses -material is not breathable
Why is nylon used for clothing and how?
- nylon is a synthetic polymer
- not waterproof on its own
- coat in polyurethane to make waterproof, tough and hard-wearing, and keep UV light out
Why do non-biodegradable plastics cause disposal problems?
- landfill sites full up quickly and the plastics will still be there years later, a waste of land and plastic
- burnt plastic releases acidic sulfur dioxide and poisonous hydrogen chloride, waste of plastic
What are chemists doing about non-biodegradable plastics?
-working on a variety of ideas to produce polymers that are biodegradable or dissolve
How to stop wasting plastics?
- reuse them
- recycle. however sorting lots of different plastics for recycling is difficult and expensive
