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junk (pd) > polymers > Flashcards

polymers Flashcards

1
Q

thermoplastic polymers

A

can be softened by heating to be reformed
- most types of modern plastics
- long chain of molecules held loosely together

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2
Q

thermosetting polymers

A
  • Permanently rigid
  • can’t be heated and reformed
  • molecules are held together by strong cross-links
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3
Q

elastomers

A
  • polymers with good elasticity
  • can be distorted under pressure, but will return to its shape
  • molecules act like strings
  • can be thermostatic / thermosetting
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4
Q

the general properties of polymers

A
  • Chemically un-reactive
  • solids at room temp
  • can be moulded into shape
  • electrical insulators
  • strong
  • heat conductivity
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5
Q

bioplastics

A

biodegradable

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6
Q

biodegradable

A

A material that will break down in the aid of natural processes - light and rain

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7
Q

examples of product using bioplstics

A

coffee cups

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8
Q

what are manufacturing methods for polymers

A
  • vacuum forming / thermos forming
  • injection moulding
  • line bending
  • calendaring
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9
Q

vacuum forming / thermos forming process

A
  • begin with a sheet of thermoplastic
  • Heated until softened
  • Two moulds connect and air is sucked out
  • cut excess / flash
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10
Q

vacuum forming / thermos forming materials

A
  • thermoplstic
  • HIP - high impact
  • PET
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11
Q

vacuum forming / thermos forming products

A
  • cycle helmets
  • packaging
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12
Q

injection moulding

A
  • plastic goes in hopper
  • goes to screw and turns whilst heating the plastic
  • then pushed into the mould
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13
Q

injection moulding materials

A
  • HDPE
  • PP
  • ABS
  • PET
  • LDPE
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14
Q

injection moulding products

A
  • toothbrush
  • lego
  • mouse and keybaord
  • lids
  • school chairs
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15
Q

line bending

A
  • plastic is heated by the bar
  • mould it to desired shape
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16
Q

line bending materials

A
  • acrylic (PMMA)
17
Q

line bending products

A
  • presentation case
18
Q

calendering

A
  • plastic enters at the top
  • compressed to desired thickness
19
Q

calendaring materials

A
  • PP
  • LDPE
20
Q

what are the ………….. moulding methods for polymers

A
  • rotational moulding
  • extrusion
  • compression moulding
21
Q

rotational moulding method

A

1 - A pre-determined quantity of thermoplashic granules / powder are put into the mould
2. - Mould goes onto an oven + spun on two axes
3 - Thermoplastic is forced to the sides of the mould by centrifugal forces
4 - Removed from heater + still rotating until cool
5 - Removed from mould

22
Q

rotational moulding materials

A
  • HDPE
  • LDPE
23
Q

rotational mould products

A
  • kayaks
  • plastic safety barriers
  • cones
24
Q

extrusion

A

Granules of thermoplastic ore fed into the hopper
-Grannules feed along the archimedian screw post the heaters where they sofren
- Softened thermoplostic of forced through a die in a continuous length
- Product travels through water baths to cool
- Part is cur to the required length

25
Q

extrusion materials

A
  • PVC
26
Q

extrusion products

A
  • guttering
  • window frames
27
Q

extrusion blow moulding method

A
  • A parison of thermoplastic is extruded into the mould
    -Mould is closed + air is blown into the parison, blowing it up so that it fills the mould
  • Allowed to cool, mould opened + the flash removed
28
Q

extrusion blow moulding materials

A
  • HDPE
29
Q

extrusion blow moulding products

A
  • gas containers
  • bottles
30
Q

compression moulding

A

A pre-determined quantity of materials in the form of o pre-form
- Placed into a heated mould
- Mould is closed with great heat † pressure.
- An irreversible reaction occurs
- Product is removed from mould + flash removed

31
Q

compression moulding materials

A
  • phenol formalahyde (bakelite)
  • urea formalde hyde-UF
32
Q

compression moulding products

A
  • bowls
  • plastic oven trays
  • car parts

junk (pd) (5 decks)

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