Polymer characteristics Flashcards
what is toughness?
the ability to absorb energy and deform plastically without cracking [bike helmet]
what is elasticity?
resistance to distortion and ability to return to its original shape [balloon]
what is flexibility?
the ability to be bent or folded without breaking [pvc film]
what is stiffness?
measure of how rigid a material is [thermosets]
what is mouldability?
ability to be shaped into a form or mould [thermoplastics]
what determines weather a polymer can be cut or scored?
its hardness
what is a thermal insulator polymer + 1 use
- insulators reduce heat transfer
- formed with air inside to make foams
- used on utensil handles [saucepans]
what are electrical insulators + 1 use
- doesn’t allow electricity to flow freely through
- used for electrical casings
what is the melting point of a polymer and what does this dictate?
- temperature it turns from a solid to liquid
- melting points dictate polymers use
what happens to thermoplastics and thermosets at high temperatures?
- thermoplastics become soft, pliable and ‘plastic’
- thermosets don’t melt but decompose and char
what is a thermoplastic?
a polymer that melts at high temperatures but solidifies when cooled
what is a thermoset?
polymer that is irreversibly hardened via curing
what does UV do to polymers and which one is UV resistant?
- UV bleaches the colour of polymers
- makes them brittle
- ABS retains its colour so is most UV resistant
what polymer is most resistant to chemicals and where is it typically used?
HDPE [high density polyethene]
used for bleach bottles and to line landfill sites
what are the differences between using PET and HDPE for drink bottles?
- both liquid resistant
- HDPE is reusable and recyclable
- PET is recyclable and can leach chemicals into the water after reuse
why are polymer films and moulded polymer used for food packaging?
- hygienically protect the food by making a barrier to oxygen, tampering and airborne threats
- prolong the shelf life to keep flavor and quality of the food
how are food bags, pots and films adapted for packaging?
- can be heat sealed
-allow cooking whilst in the packaging
[ready meals]
how do additives increase the biodegradability of thermoplastics?
- thermoplastics degrade slowly and leave plastic particles polluting the soil
- bio-batch additives allow the thermoplastic to be broken down quicker by natural bacteria
what is recycling?
process of recovering waste and reprocessing it into useful products
what does recycling do to polymers?
- prevents it ending up in landfill
- reduces the production of new material from finite resources
what are finite resources?
non-renewable [coal]
why are polymers self finishing?
- they require no additional surface finishing
- they take the surface of the mould they were in
- pigments can be added to reduce the need for secondary surface colouring
what 2 things do plasticisers do?
enhance flow characteristics so polymers can be moulded at higher temperatures
also make polymers streatchy
what do thermal antioxidants do?
help prevent oxidation due to heat exposure
what do lubricants do?
improve polymer flow by decreasing viscosity
what do antioxidants do?
reduce degradation from air and water to prevent cracking and discolouration
what do UV light stabilizers do?
improve the resistance to UV radiation
what do fire retardants do?
increase fire resistance
what do antistatic additives do?
reduce the build up of static charge
what 6 stock forms are polymers found in?
sheet, film, granules, extruded [rods], foam and powder
what are the 3 different types of polymer sheet with 1 characteristic?
- solid cast [extruded]- acrylic for kitchens
- fluted sheet- has channels in it for folders
- laminated sheet- foam board has 2 card around 1 foam layer
how can polymer sheets be used?
in their flat form and can be cut or moulded
what are the 4 types of film?
packaging, membranes, carrier bags and photographic
why are granules used for moulding?
- easier to process
- easier to measure
- melt quicker
where are plastic granules used?
- playground surfaces
- filling stuffed toys
- cosmetic products
how do you make polymer granules into a rod? +1 use
- Nylon and PP granules are melted
- extrusion forms them into a continuous profile
- bearings and gears
what polymers can undergo extrusion?
PVC, PP and HDPE
what products are made by extruding polymers?
- window frames
- tubing
- seals and mouldings
- adhesive tapes
- wire insulation
what ingredients make foam?
polymer with additive/catalyst, heat, air or gas
what happens when foam is mixed?
- expands
- gas bubbles form and pop
- makes a spongy porous form
what can foam be used for?
- exercise mats
- packaging
- insulation
- soft furnishings
- model making
what are powder polymers used for?
- protect metals from corrosion
- for 3D printing when laser cured
how are metals painted with powder?
- metals are electrically charged or heated
- dipped or spayed in powder
- then cured
what are the properties of foam board? +1 use
- lightweight
- easy to cut and score
- solvents can melt it
- presentation boards and model making
what are the properties of Fluted Polypropylene +1 use
- creases
- bends
- integrated channels
- folding boxes, folders and signage
what are the properties of translucent PP + 1 use
- tough
- tear resistant
- water resistant
- printed or laser cut
- flexible
- coloured or clear
- document folders, lightweight boxes
what is Styrofoam?
dense, extruded blue foam
what are the properties and uses of styrofoam?
- available in sheets or blocks
- comes in a range of thicknesses
- cut and shaped
- used for model making or moulds/formers
Properties of LDPE and where is it used?
- tough, flexible sheet
- good chemical resistance
- thin films or sheets
- food wrap, bags [bin/freezer], bubble wrap
what are the properties of Plastazote [engineered foam] and its uses?
- tough , flexible and lightweight
- impact resistant
- insulator
- yoga mats or pipe covers
- protective packaging
what is cellulose acetate and its properties?
naturally derived biodegradable film
- tough
- transparent
what are 2 uses for cellulose acetate?
- photographic film
- biodegradable packaging
what is Polylactide acid [PLA] and what are its properties?
- biodegradable polymer
- recyclable
- compostable
- low impact resistance
what is PLA made from and why is this a problem?
- corn starch and sugar beet
- requires a large amount to make the polymer
what is PLA used for?
replaces PET for biodegradable packaging
what is transparency?
how permeable a material is to light radiation
what is translucent?
when some light can pass through but is diffused so the object isn’t clear to see
what is opaque?
when the material is impermeable to light
