Plastics (polymers)

Plastics (polymers)

1. Properties of plastics

   • Thermoplastic
     • a.k.a Thermosoftening
     • Recyclable
       • E.g. Plastic bottle
     • Soft
     • Covalent forces between polymer chains are weak
       • Cannot be re-melted/re-moulded
   • Thermosetting
     • Unrecyclable
     • Hard & Brittle
     • Covalent forces between polymer chains are strong (cross links)
       • Cannot be re-melted/re-moulded

2. Monomer

   • Ethene
     • Addition reaction (polymerisation)
       • Polyethene
         • Easy to shape
           • Most common plastic
         • PE
           • Non-biodegradable
             • Incineration
             • Landfill
             • Recycling
             • Not broken down in soil
               • Harms wildlife
               • Unsightly
               • Take up space
       • Double bonds gets replaced my single bonds
     • Ethene + Steam (H20)
       • Ethanol
         • Fermentation reaction
           • Sugar --> Ethanol + CO2
             • Ethanol
               • Biofuel
           • By doing this: we are conserving crude oil supplies
   • Propene
     • Addition reaction
       • Polypropene
         • Tough plastic
   • Double bonds gets replaced by single bonds
     • Polymer
       • PET
         • Soft drink bottles
           • Recycled to make t-shirts
           • Strong and light
         • Using old plastics for useful things
           • By doing this; we are conserving crude oil supplies
   • Cracking
     • Long-Chain hydrocarbon (alkane)
       • Fractional distillation
         • Crude oil
     • Splitting a long-chain hydrocarbon (using AlO catalyst - broken pot) into a bigger alkane and smaller alkene
       • Bromine water test for an alkene

3. Smart Polymers

   • Light-sensitive polymers
     • Plaster less sticky in light
       • Less painful for elderly (thin skin) and young (sensitive skin)
   • Shape-memory polymers
     • Properties changed by light, temp or other changes in their surroundings
     • E.g. Dissolvable stitches tighten and close the wound as body temp goes up
   • Hydrogel plaster
     • Keeps wound moist and promotes healing
     • Contains 90% water

4. Bioplastic (100% cornstarch plastic)

   • PLA
     • 100% Biodegradable

5. Plastic mixed with cornstarch

   • Biodegradable
     • Plastic breaks into very small pieces
     • Broken down in soil by action of microorganisms