Polymers Flashcards
Acrylic properties a few uses
- hard
- can be transparent
- resistance to weathering
- scratches easily
- stiff
- brittle
- good electrical insulator
signs + covers for car lights
HIPs properties and a few uses
- tough
- impact resistant
- lightweight
- hard
kids toys, yoghurt pots, fridge liners
HDPE properties and a few uses
- hard
- stiff
- great chemical resister
plastic bottles, tubing pipes
Polypropylene properties and a few uses
- tough
- hard
- fatigue resistant
- good chemical resistant
- lightweight
- flexible
- scratches easily
Toys, DVDs, food packaging, bottle caps
What is epoxy resin and uses
- Mixed with a hardener and left to set
- Can be used to make adhesives and flooring
What is melamine formaldehyde (MF) and uses?
- Scratch, water and stain resistant and is harder
- used to laminate work surfaces children’s cups and dishes
What is phenol formaldehyde and uses
- Tough and heat resistant
- often in black in colour
- used for saucepan handles
What is polyester resin (PR) and uses?
- Combined with fibreglass
- produce GRP
- used for pipes
What is urea formaldehyde (UF) and uses?
- Hard
- brittle
- rigid
- excellent insulator
- used for plug, sockets, switches, and toilet seats
What are the four key stages/processes of polymers?
- Crude oil is extracted from the Earth to
- The oil is processed in a refinery factory to separate different component compounds (fractional distillation) which are cracked to make monomers then linked to make chains called polymers
- Plastic is initially made into millions of pellets (a stock form)
- The pellets are melted, then moulding into shapes by manufacturers.
What are the stock forms of polymers?
- Sheets
- rods
- powders
- granules
- foam
- films
They are sold by length, width, gauge and diameter
Injection moulding and some examples
- Most widespread and versatile process
- high set up costs, low production costs
- mass produced items
- Dimensions and shapes can be accurately controlled
- goes into the hopper, spun around on the screw and injected into the mold
kettles, toys and chairs.
Blow molding and some examples
- Short tube of extruded plastic is trapped in an mold
- air is blown so plastic takes the shape of the mould and cavity.
Typical products are bottles made from PET or PP
Extrusion and some examples
- A form of moulding that makes a continuous shape
- It goes into the ram and then gets chopped so all parts are equal
a straw or curtain rod or plastic sheet or pipe or garden hose 
Vacuum forming and some examples
- Produces simple shapes from the thermoplastic sheet
- sheet is heated until soft then vacuum drawers material over mold
- Commonly used materials include HDP and HIP and PVC
- mold must be produced with a draft angle at least 3°
toys and pill packaging 💊
Bending and forming acrylic, and uses
- Heating a thermoplastic sheet over a strip/line heater until it becomes soft and pliable then bending it usually a former
- Thermoplastics can be bent using a jig or a former or if the angle is not critical simply bending it by hand and then holding it until it is cool
Karim Rashid Oh Chair
How does injection moulding work?
- granular plastic is held in a hopper
- it is moved via an
Archimedean screw
along a heated tube, called the heating chamber - once the polymer has been melted, it is pushed into a mould with a
hydraulic ram
- the use of the hydraulic ram ensures just enough material is injected into the mould each time - the mould is then cooled so that the moulded plastic can be removed
How does extrusion work?
- granular plastic is held in a hopper
- it is moved by Archimedean screw along a heated tube, called the heating chamber
- once the polymer has been melted it is pushed through a die mould, which will form the shape of the extrusion
- because there is no hydraulic ram in this process, molten plastic can be fed through the die continuously
What are the forces that can be acted on a material?
- tension - a pulling force
- compression - a pushing force
- bending - forces at an angle to the material
- torsion - a twisting force
- shear - forces acting across the material
Common polymer Shorthand Common use
Polyethylene terephthalate PET Plastic water bottles
High density polythene HDPE Fabric conditioner bottle
Polyvinyl chloride PVC Plastic toys, cling film, blister packs
Low density polythene LDPE Bread bags
Polypropylene PP Yogurt pots and pen lids
Polystyrene PS Packaging and coffee cups
