polymers

Question 1

what are ways to classify type of polymer based on geometric structure?

Answer 1

configuration
conformation
positioning of side groups on main chain
branding
copolymers

Question 2

what is conformation?

Answer 2

order that arises from rotation of molecules

Question 3

what is configuration?

Answer 3

order determined by chemical bonds

Question 4

when can configuration be altered?

Answer 4

only when chemical bonds are broken and reformed

Question 5

what are copolymers?

Answer 5

polymers that incorporate more than one kind of monomer into their chain

Question 6

what type of order does a crystalline structure have?

Answer 6

high degree of

Question 7

what type of order do amorphous structures show?

Answer 7

no long range

Question 8

what is melting point of polymers like and why?

Answer 8

semi crystalline so melts over a range of temperatures

Question 9

what sort of structure do short chains have?

Answer 9

crystalline

Question 10

what are the forces in crystalline structures?

Answer 10

weak van der waals forces

Question 11

what type of DP do amorphous structures have?

Answer 11

high

Question 12

which factors affect whether you get crystalline or amorphous structures?

Answer 12

polymer chain length
monomer size and shape
cooling rate

Question 13

what sort of structures do we get for Tg below room temperature?

Answer 13

elastomers

Question 14

what sort of structures do we get for Tg above room temperature?

Answer 14

rigid, structural polymers

Question 15

what are polymers like below Tg?

Answer 15

brittle

Question 16

what are polymers like above Tg?

Answer 16

rubbery

Question 17

what does time-dependent deformation behaviour mean?

Answer 17

strain rate changes depending on rate of application of force, which affects apparent Tg

Question 18

what is injection moulding?

Answer 18

injecting liquid polymer into a mould

Question 19

what happens in extrusion moulding?

Answer 19

continuous flow of liquid polymer is sent through a die to give constant cross-sectional form

Question 20

what happens in extrusion blow moulding?

Answer 20

liquid plastic is extruded to a hollow tube and sealed in a mould, and compressed air inflates tube to form shape of mould to form a hollow object

Question 21

what happens in rotational moulding?

Answer 21

plastic placed in mould which is rotated and plastic moves to walls by centrifugal force which forms large hollow objects

Question 22

what happens in thermoforming?

Answer 22

plastic sheet is placed in an oven then stretched onto a mould, then cooled

Question 23

what happens in compression moulding?

Answer 23

thermosetting plastics placed in mould, mould closed and pressure applied until material has hardened

Question 24

what is a thermosetting plastic?

Answer 24

ones that irreversibly harden after cooling

Question 25

what is calendaring?

Answer 25

continuous process to form sheets/films of plastics

Question 26

what happens in calendaring?

Answer 26

plastic placed in roll mill then fed onto heated rollers

Question 27

what happens in pultrusion?

Answer 27

plastics are pulled through a die

Question 28

what properties do ceramics have?

Answer 28

high durability resistant to corrosion brittle weak

Question 29

what are high performance engineering ceramics like?

Answer 29

well controlled microstructure so have excellent mechanical properties

Question 30

what do we have to do for manufacturing engineering ceramics?

Answer 30

reduce size and number of defects

Question 31

what are melting points of engineering ceramics like?

Answer 31

high

Question 32

how are ceramics made?

Answer 32

powders are compressed and fired