C2 - Polymers

Seite 1

Polymers

Forces between molecules determine the properties of Plastics

Weak forces: Individual chains of molecules are held together by weak inter-molecular forces.

(They are free to slide over one another)

Strong Forces: Chains are held together by strong inter-molecular forces called crosslinks.

(The chains are held firmly together)

THERMOSOFTENING POLYMERS

THERMOSETTING POLYMERS

Thermosoftening Polymers:

Have low melting points as forces are easy to overcome.

Hardens when cooled.

Easy to remould into different shapes as many times as you like.

Thermosetting Polymers:

Crosslinks hold them together in a solid structure.

Does not soften when heated.

They are strong, hard and rigid.

Low Density (LD) Polythene is produced when ethene is heated to 200 degrees under high pressure

(It is flexible, used for bags and bottles)

High Density (HD) Polythene is produced at a lower temperature and pressure with a catalyst

(It is more rigid, used for pipes and water tanks)

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