The Structure and Properties of Polymers
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Slide 11

Thermosets

Extensive cross-linking formed by covalent bonds.

Bonds prevent chains moving relative to each other.

What will the properties of this type of plastic be like?

Slide 12

Critical length needed before strength increases.

Hydrocarbon polymers average of 100 repeating units necessary but only 40 for nylons.

Tensile strength measures the forces needed to snap a polymer.

More tangles + more touching!!!

Slide 13

Areas in polymer where chains packed in regular way.

Both amorphous and crystalline areas in same polymer.

Crystalline - regular chain structure - no bulky side groups.

More crystalline polymer - stronger and less flexible.

Slide 14

When a polymer is stretched a ‘neck’ forms.

What happens to the chains in the ‘neck’?

Cold drawing is used to increase a polymers’ strength. Why then do the handles of plastic carrier bags snap if you fill them full of tins of beans?

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