Polymers Flashcards
What determines the properties of plastics?
The forces between molecules
What type of bond holds the atoms of a polymer in long chains?
Strong covalent bonds
What are the forces between molecules known as?
Intermolecular forces
What are the 5 properties of thermosoftening polymers?
- Individual strands
- Weak intermolecular forces- strands free to slide over eachother
- easy to break chains- MELT
- When it cools, the polymer hardens into a new shape
- You can melt and remould them infinately
What are the properties of thermosetting polymers?
- Have cross-links between strands (strong intermolecular forces)
- Its strands are thus held together in a solid structure
- Doesn’t soften when heated
- Strong, hard, and rigid
Which type of polymer has stronger intermolecular forces? Thermosetting or thermosoftening?
Thermosetting has stronger intermolecular forces
Which 2 parts of making a polymer affect its properties?
- The starting materials
2. The reaction conditions
How is low density (LD) polythene made?
By heating ethene to about 200 degrees C under high pressure
What is low density (LD) polythene used for (2) and why?
bags and bottles because of its flexibility
How is high density (HD) polythene made?
At a lower temperature and pressure to LD polythene with a CATALYST
What is high density (HD) polythene used for (2) and why?
water tanks and drain pipes because it is rigid
What are the key properties for a plastic disposable cup?
low cost (disposable), high melting point (hot drinks)
What are the key properties for a plastic measuring cylinder?
high transparency (see liquid), resistant to chemicals (liquids mustn't react with cylinder)
What are the key properties for plastic clothing?
flexible (so can wear), able to be made into fibres (clothing usually woven
