Polymers Flashcards
How are plastics made
synthetic plastics have replaced wood/metal in manufacturing, commercial production of plastics really started after WWII. The raw materials are coal/oil. Contain a number of different chemical which can be sperated into parts - fractional distillation
Plastics manufacture - How is it formed into products
plastic products are made by heating the plastic and using a mould, a former or a cast
Why is plastic used compared to other materials
it is cheaper than similar products made from wood/metal because:
raw materials and extraction is cheaper, less energy is needed to make the product, products = easily mass produced, transport costs are less
What are the problems in using plastics
they have a long shelf life which means they are difficult to dispose of aa they don’t rot or corrode, if burnt they product black choking gasses, production of plastics = polluting, PVC contains nasty pollutants and difficult to recycle, when molten they are sticky and cause severe burns, thermoplastics can be recycled by reforming but limited with frequent heating, sustainability = designers have to take into consideration 6r’s
Thermoplastics definition
weak bonds break allowing the plastic to become semi-fluid and reshaped, the physical structure is changed not a chemical change, process can be repeated if not overheated so they are recyclable
Name the different types of thermoplastic
polyethylene terephthalate (PET), high density polythene (HDPE), Low density polythene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), Acrylic (PMMA), polycarbonate, ABS
AD and DIS of polyethylene terephthalate (PET) and common uses
AD - easily recyclable
DIS - one time use
CU - clothing, container of food an liquid
AD and DIS of high density polythene (HDPE) and common uses
AD - tough, can be blow moulded, can be extrusion injection moulded
DIS - brittle
CU - bottles (bleach), toys, buckets, piping - medium use items
Low density polythene (LDPE) common uses
CU - thin film, carrier bags, wiring insulation, squeezy bottles
AD and DIS of polyvinyl chloride (PVC) and common uses
AD - strong, stiff, chemical and weather resistance
DIS - toxic fumes released during production
CU - window frames, gutters, disposable pens
AD and DIS of polypropylene (PP) and common uses
AD - versatile, flexible without breaking, withstand variable temp
DIS - low UV resistance
CU - garden furniture, tubs, binders - long use items
Different types of polystyrene (PS) and common uses
expanded polystyrene = packaging - light and impact absorbent
high impact polystyrene = vacuum forming - household items as good impact strength, rigid
AD and DIS of Acrylic (PMMA) and common uses
AD - strong, good insulator, can be: vacuum formed, line bent, blow moulded
DIS - scratches easily
CU - car headlights, street signs
AD and DIS of polycarbonate (PC) and common uses
AD - high strength, transparent, good resistors of heat/chemicals
DIS - can be scratched
CU - CD packaging, bus shelters, car lights
AD and DIS of ABS and common uses
AD - strong, tough, scratch resistant, impact resistant
DIS - low melting point
CU - lego, kettles, vacuum cleaners
Thermoset definition
they undergo a chemical change so once heated/chemically changed this is their final form as they form strong bonds, it is difficult to injection mould as heat changes them immediately which means they can’t be recycled
Name the different types of thermoset plastics
urea formaldehyde, melamine formaldehyde, polyester resin, epoxy resin
AD and DIS of urea formaldehyde and common uses
AD - hard, good insulator
DIS - brittle
CU - electrical plugs, sockets, switches
AD of melamine formaldehyde and common uses
AD - scratch/water/stain resistant
CU - laminate in kitchen work surfaces, hard small heat resistant products - cup/dishes
AD and DIS of polyester resin and common uses
AD - combined with fibreglass to produced glass reinforced plastic
DIS - toxic fumes
CU - boat hulls, car parts
Epoxy resin common uses
mixed with a hardener and left to set
CU - adhesives, flooring
How to finish acrylic when hand cut and why is this nessersary
hand cutting leaves marks so you would cross file first, then draw file and then sand it with wet and dry paper (P800+)
Elastomers definition
thermosetting, it has a springy bond some like rubber can be vulcanised to make them rigid, they can be stretched repeatly and still return to their original shape, non-toxic, often used on top of other products
Name the different types of elastomers
natural rubber, butadiene rubber (BR), neoprene, silicone
AD and DIS of natural rubber and common uses
AD - good hardness in comparison to other elastomers, good cold resistance, widely used and available
CU - tyres
Butadiene rubber common uses
CU - mostly tyre production, additives to polystyrene, synthetic rubber
Neoprene common uses
CU - laptops sleeves, remote controls, mouse pads, lifestyle and home accessories
AD and DIS of silicone and common uses
AD - biocompatible, hypoallergic, does not react with most chemical/biological processes
CU - suitable for baby care products/food, medical use
Biodegradable polymers definition
most polymers care made from non-renewable finite sources, polymers can be produced from cellulose (wood, sugar, starch), biopolymers can be split into 2 categories - natural/synthetic,
Polymer degradation definition and give the definitions of the types of degradation
polymers degrade due to chemical/heat/light
2 main types:
- polymer is made from finite resources but has additive designed to make it break down faster (5 years),
- polymer breaks down due to micro-organisms
Name the different types of biodegradable polymers with additives
oxy-degradable polymers, photo gradable polymer, hydro degradable polymer
Definition of oxy-degradable polymers
the polymers break down into a fine powder with oxygen through microorganisms
Definition of photo gradable polymers
breaks down with uv, used in agriculture
Definition of photo hydro polymers
breaks down with exposure to water, used in liquid detergent sachets
Implications of biopolymers
release methane gas - global warming - toxic, need land to grow - can’t be recycled
Name the different types of biodegradable polymers without additives
corn-starch polymers, potatoPAK, PHA and PHB, PLA, lactide glycoclide
Definition, AD and common uses of corn-starch polymers
made from veg starch
AD - biodegradable if composted and can be used for animal feed, sustainable. readily decompose
CU - packaging
Definition, AD and common uses of PotatoPAK polymers
potato starch, cellulose, water = heated and pressed into shape
CU - bowls, cutlery, food trays
Definition, AD, DIS and common uses of PHA and PHB
polymer produced by natural microorganisms
AD - brittle, stable, strong, moulded easily
DIS - little chemical resistance
CU - bottles, food items, household items
Definition, AD and common uses of PLA
made from renewable biomass
AD - non-toxic, easily moulded, can be made in a range of colours and textures
CU - bottles, food packaging, 3D printer filament
Definition common uses of lactide, glycoclide
additives
CU - food wraps, bags, bin bags
Polymer finishing definition
polymers are self finishing, any finishes like textures and pigments are ‘additives’ that re included during the processing or textures on the mould
Name the different types of polymer finishes
acrylic spray paint, over moulding
Acrylic spray paint definition
requires preparation and can be added to change colour or colour match existing parts, most cost effective to spray colour than change pigment for each part
Over moulding definition
usually a rubbery plastic added to the main product to improve grip, injection moulded as 2 separate pieces or twin injection
Poly enhancements definition
(not finishes) - characteristics can be enhanced to improve working properties/aesthetics
What machining properties can be changed in polymers
Machining properties:
lubricants can be added to make the plastics flow better into moulds during manufacture
Thermal antioxidants can be added to stop discolouring during manufacture
What aesthetics properties can be changed in polymers
pigments can be added prior to manufacture to change colour, these are small particles added into the mix before forming the product
What functional properties can be changed in polymers
antistatic additives are added to avoid static build up on electrical insulating parts, flame retardants are added to reduce likelihood of plastics catching fire, plasticisers are added to make the plastic less brittle, fillers can be added to bulk out the material requiring less plastic and/or minerals can be added to help with thermal conductivity
What life extension properties can be changed in polymers
antioxidants can be added to prevent degradation form oxygen, UV stabilisers can be added to prevent degradation from sunlight, this usually stops materials becoming brittle or loosing colour
What degradation properties can be changed in polymers
biodegradable plasticisers can be added to speed up degradation
