1. Plastics Topic 13

2. Properties of Plastics Flexible – you can squeeze the shampoo out of the bottleFlexible – you can squeeze the shampoo out of the bottle Watertight – the shampoo will not leakWatertight – the shampoo will not leak Shatterproof – the bottle won’t break if dropped.Shatterproof – the bottle won’t break if dropped. Light – easy and cheap to transportLight – easy and cheap to transport Easily moulded – can make plastic into complicated shapesEasily moulded – can make plastic into complicated shapes Heat insulators – plastic vending machine cups.Heat insulators – plastic vending machine cups. Durable, non biodegradableDurable, non biodegradable Electrical insulators – plugs and sockets are made of plasticElectrical insulators – plugs and sockets are made of plastic

3. What happens when we heat up plastic? Two groups of plastics:Two groups of plastics: Thermoplastic – materials soften on heating so can be moulded into new shapesThermoplastic – materials soften on heating so can be moulded into new shapes Thermosetting – plastics that do not soften when heated, so cannot be remoulded.Thermosetting – plastics that do not soften when heated, so cannot be remoulded.

4. Problems with Plastics Non-biodegradable – do not decay when thrown awayNon-biodegradable – do not decay when thrown away Large amounts of plastic thrown away which ends up in landfill sitesLarge amounts of plastic thrown away which ends up in landfill sites Some local authorities burn plastics to dispose of them – needs to be controlled to prevent dangerous fumes from being producedSome local authorities burn plastics to dispose of them – needs to be controlled to prevent dangerous fumes from being produced

5. Solutions Re-use plastics – e.g. plastic bagsRe-use plastics – e.g. plastic bags Recycle at recycling points and at homeRecycle at recycling points and at home Use biodegradable plastics – decay when they come into contact with the soilUse biodegradable plastics – decay when they come into contact with the soil Use less plastic - manufacturers could use less for packagingUse less plastic - manufacturers could use less for packaging

6. Burning Plastics Most of the poisonous fumes which burning plastics produceMost of the poisonous fumes which burning plastics produce are made when elements in the plastics join with oxygen in the air are made when elements in the plastics join with oxygen in the air to form new compounds. to form new compounds. Plastic Toxic Gas Produced All plastics CarbonMonoxide PolyurethaneplasticsHydrogencyanide Poly(chloroethene) Hydrogen chloride

7. Natural vs. Synthetic AdvantagesDisadvantages Natural Materials e.g. wool, wood, paper Biodegradable Can be expensive Made from renewable resources e.g. trees Don’t last very long Synthetic Materials e.g. plastics Are long-lasting Non-biodegradable Mass produced cheaply Made from oil – finite resource Useful properties – light, flexible Toxic fumes when burned

8. Polymers Plastics are very large molecules called polymers – ‘poly’ – many; ‘mer’- a partPlastics are very large molecules called polymers – ‘poly’ – many; ‘mer’- a part This molecule is called polythene

9. Making Plastics The plastic polythene is made by joining molecules of ethene.The plastic polythene is made by joining molecules of ethene. The small ethene molecules that join together to form the polymer are known as monomersThe small ethene molecules that join together to form the polymer are known as monomers Its correct name is poly(ethene) – to name a polymer/plastic ‘poly’ then the (monomer unit) in bracketsIts correct name is poly(ethene) – to name a polymer/plastic ‘poly’ then the (monomer unit) in brackets Poly(ethene) is the most widely used plasticPoly(ethene) is the most widely used plastic

10. Making Poly(ethene) Many ethene molecules Many ethene molecules This process is known as polymerisation

11. Polymerisation Polymers are formed when small molecules known as monomers join togetherPolymers are formed when small molecules known as monomers join together All the monomers in this kind of polymerisation must contain C = CAll the monomers in this kind of polymerisation must contain C = C Each small monomer becomes a part of the polymerEach small monomer becomes a part of the polymer

12. Addition Polymerisation Addition polymerisation is an important type of polymerisation and is a complicated process.Addition polymerisation is an important type of polymerisation and is a complicated process. Always starts with a monomer with aAlways starts with a monomer with a C = C bond (usually found in Alkenes) C = C bond (usually found in Alkenes) Polymerisation begins with the breaking of the C = C – a catalyst is requiredPolymerisation begins with the breaking of the C = C – a catalyst is required

13. Addition Polymerisation Thousands of monomer units link together to form the polymerThousands of monomer units link together to form the polymer For the formaiton of polyethene this can be represented as:For the formaiton of polyethene this can be represented as: nC 2 H 4  (C 2 H 4 )n Where n = the number of molecules

14. Addition Polymerisation of Ethene Ethene monomersEthene monomers ….+ + …. ….+ + ….Poly(ethene)

15. Summary Questions 1.State what is meant by non – biodegradable 2.Explain what is meant by the term thermosetting 3.What is the name for a type of plastic that can be reshaped upon heating? 4.What is the raw material for plastics?