polymers Flashcards
thermoplastic polymers
can be softened by heating to be reformed
- most types of modern plastics
- long chain of molecules held loosely together
thermosetting polymers
- Permanently rigid
- can’t be heated and reformed
- molecules are held together by strong cross-links
elastomers
- polymers with good elasticity
- can be distorted under pressure, but will return to its shape
- molecules act like strings
- can be thermostatic / thermosetting
the general properties of polymers
- Chemically un-reactive
- solids at room temp
- can be moulded into shape
- electrical insulators
- strong
- heat conductivity
bioplastics
biodegradable
biodegradable
A material that will break down in the aid of natural processes - light and rain
examples of product using bioplstics
coffee cups
what are manufacturing methods for polymers
- vacuum forming / thermos forming
- injection moulding
- line bending
- calendaring
vacuum forming / thermos forming process
- begin with a sheet of thermoplastic
- Heated until softened
- Two moulds connect and air is sucked out
- cut excess / flash
vacuum forming / thermos forming materials
- thermoplstic
- HIP - high impact
- PET
vacuum forming / thermos forming products
- cycle helmets
- packaging
injection moulding
- plastic goes in hopper
- goes to screw and turns whilst heating the plastic
- then pushed into the mould
injection moulding materials
- HDPE
- PP
- ABS
- PET
- LDPE
injection moulding products
- toothbrush
- lego
- mouse and keybaord
- lids
- school chairs
line bending
- plastic is heated by the bar
- mould it to desired shape
line bending materials
- acrylic (PMMA)
line bending products
- presentation case
calendering
- plastic enters at the top
- compressed to desired thickness
calendaring materials
- PP
- LDPE
what are the ………….. moulding methods for polymers
- rotational moulding
- extrusion
- compression moulding
rotational moulding method
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
rotational moulding materials
- HDPE
- LDPE
rotational mould products
- kayaks
- plastic safety barriers
- cones
extrusion
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
extrusion materials
- PVC
extrusion products
- guttering
- window frames
extrusion blow moulding method
- 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
extrusion blow moulding materials
- HDPE
extrusion blow moulding products
- gas containers
- bottles
compression moulding
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
compression moulding materials
- phenol formalahyde (bakelite)
- urea formalde hyde-UF
compression moulding products
- bowls
- plastic oven trays
- car parts
