Week 7: Plastics/Polymers

Question 1

Thermoplastics

Answer 1

A class of polymers which refers to those which are solid at room temperature and has a repeatable process of melting down and moulding.

Question 2

Thermosets

Answer 2

A class of polymers which are stronger than thermoplastics and are better suited for high temperature situations.

Question 3

What are the 3 main classes of polymers?

Answer 3

Elastomers, thermoplastics and thermosets

Question 4

What is a composite material?

Answer 4

One that is made up of 2 or more materials and has the properties of those use to make it

Question 5

What is tacticity used for?

Answer 5

It helps determine the degree of crystallinity. The more tacticity the more crystalline a polymer is

Question 6

What are the 3 types of tacticity?
ISA

Answer 6

Isotactic, syndiotactic and atactic

Question 7

What does the glass temperature mean for semicrystalline polymers mean?

Answer 7

It means that the amorphous regions are not moving and are almost in their frozen stage.

Meaning that at low temperatures the amorphous region is in a glassy state.

Question 8

What does the melting temperature mean for semicrystalline polymers mean?

Answer 8

It means that at higher temperatures the crystalline region is vibrating enough so that it becomes disordered.

Question 9

What does the glass temperature mean for amorphous polymers mean?

Answer 9

It means that the temperature is low enough to the point where the amorphous region can’t vibrate or move and so it will be brittle and hard in nature.

Question 10

Why isn’t there a melting temperature for amorphous polymers?

Answer 10

This is unique only to semicrystalline because they have structured regions that become disorganised when heated to higher temperatures.

Amorphous polymers are already disorganised so there can’t be a change to them.

Question 11

What happens when a polymer has a high degree of crystallinity?

Answer 11

It’s stiffer, harder, more brittle and heat resistant

Question 12

What property of temperature applies to both semicrystalline and amorphous polymers?

Answer 12

The glass temperature

Question 13

What happens when a polymer has a low degree of crystallinity?

Answer 13

It’s less dense, more ductile and flexible.

Question 14

What is orientation of plastics?

Answer 14

It’s the process to improve the degree of crystallinity

Question 15

How do you improve the orientation of semicrystalline polymers?

Answer 15

Stretch at ambient temperatures

Question 16

How do you improve the orientation of amorphous polymers?

Answer 16

Stretch at elevated temperatures

Question 17

Spherulites

Answer 17

Radial growth of polymers that are made up of lamellas and amorphous regions.

Question 18

What are the steps in growth for a polymer?

Answer 18

Monomers -> polymers -> polymer chains -> Lamellas and amorphous regions -> Spherulites

Question 19

What are the 3 types of tacticity?

Answer 19

Isotactic, syndiotactic & atactic

Question 20

Isotactic

Answer 20

All groups on the same side of polymer chain

Question 21

Syndiotactic

Answer 21

Groups alternate on either side of the polymer chain

Question 22

Atactic

Answer 22

Grouping is irregular

Question 23

Which tacticity is related to semi-crystalline behaviour and amorphous behaviour?

Answer 23

Semi-crystalline: Istotactic & syndiotactic

Amorphous: amorphous