5. Plastics Flashcards
name the two types of plastic
Thermoplastics
Thermosetting Plastics
Name 4 forms plastic is available in
Sheets Rods Tubes Bars Thin layers of film Foam Paint/varnish
True or false?
Thermosetting plastics can be remoulded several times.
False, thermosetting plastics can only be moulded once.
Name 4 thermosetting plastics.
Epoxy Resin
Melamine Formaldehyde
Urea Formaldehyde
Polyester Resin
What are the properties of epoxy resin?
Excellent adhesive qualities
Strong when reinforced
What are the uses of epoxy resin?
Bonding
Laminating
surface coating
What are the properties of melamine formaldehyde?
Waterproof
Odourless
Mark and scratch resistant
What are the uses of melamine formaldehyde?
Worktops
Tableware
Buttons
Electrical Insulation
What are the properties of urea formaldehyde?
Good adhesive qualities Stiff Hard Brittle Good electrical insulator
What are the uses of urea Formaldehyde?
Electrical fittings
Paper and textile coating
Wood adhesive
What are the properties of polyester resin?
Stiff
Hard
Brittle
Formed without heat or pressure
What are the uses of polyester resin?
Panels for car bodies and boat hulls
Casting
Embedding
Can thermoplastics be remoulded?
Yes, they can be moulded as many times as needed as they can be softened and remoulded if they are heated.
Name 5 thermoplastics
High density polythene Low density polythene Polypropylene Polystyrene Acrylonitrile Butadiene Styrene (ABS)
What are the properties of high density polythene?
Tough
Chemical resistant
Feels waxy
What are the uses of high density polythene?
Buckets
Bowls
Sterilised containers
What are the properties of low density polythene?
Soft
Pliable
Electrical insulator
Flexible
What are the uses of low density polythene?
Bags
Bottles
Cable sheathing
Toys
What are the properties of polypropylene ?
Rigid Light Good chemical resistance Resistance to fatigue Bending
What are the uses of polypropylene?
Crates Seats String Rope Medical equipment Kitchenware
What are the properties of polystyrene?
Light
Buoyant
Stiff
Water resistant
What are the uses of polystyrene?
Packing containers
Insulation
Toys
What are the properties of ABS?
Strong Light Durable Scratch/chemical resistant High surface finish
What are the uses of ABS?
Kitchenware Toys Cases Crash helmets Telephones
List the three steps in injection ion moulding
- Plastic powder is fed into hopper
- A motor turns a thread which pushes the granules along the heated section, melting it to a liquid.
- Liquid is forced into a mould where it cools into the shape.
name 4 advantages to injection moulding
Complex shapes Accuracy Mass manufacture - fast production rates Texture can be applied High quality surface finish - no further finish required Fine detail - integral parts Material flexibility Low waste
What are the identifying features of injection moulding?
Sprue Marks Draw Angles Mould Split Lines Ejection Pin Marks Webs for Strength
List the three steps involved in extrusion
- A motor turns a thread which feeds granules of plastic through a heater.
- The granules melt into a liquid which is forced through a die, forming a long ‘tube like’ shape.
- The extrusion is then cooled and forms a solid shape.
What are the advantages of extrusion?
Uniform cross section Availability in length repeatability Accuracy High quality surface finish
What are the identifying features of extrusion?
Smooth Walled
Long Sections
Uniform Thickness and Shape
Line Texturisation
List the 4 steps in Vacuum forming
- Plastic sheet is placed above the mould and clamped securely
- Electric heater switched on to heat up plastic sheet until it becomes flexible
- Shelf is raised and vacuum is switched on so air is removed from area below the plastic to wrap around the mould
- Vacuum is turned off, shelf lowered and the product will then be ready for trimming
Name the advantages of vacuum forming.
Economies of scale- large numbers can be produced
Low cost- thin large sheets of plastic, large quantities
Low quality design for throw away products
What are the identifying features of vacuum forming?
Material is usually thin
Patterns/texture are transferred from mould
Tapers are pronounced/obvious
Thinning on sides
What plastics are used for injection moulding?
Polypropylene
High density polythene
Polystyrene
What plastics are used for extrusion?
Polypropylene
High density polythene
PVC
What plastics are used for vacuum forming?
High density polythene
List the steps in compression moulding.
- A piece of plastic is placed in the mould and heated up until soft and malleable
- The hydraulic press moves down and the plastic is compressed into the shape of the mould
What plastics are used in compression moulding?
Melamine formaldehyde
Urea formaldehyde
Name 4 advantages of compression moulding
Products withstand heat/electrical damage High volume produced Complex shapes Little material waste Accuracy Repeatability Thermosetting plastics only quality surface finish/detail
What are the identifying features of compression moulding?
Walls have uniform thickness (usually 3-6mm)
Quality surface finish
What are the three steps involved in blow moulding?
- The plastic is heated until soft and malleable and put into the mould. The plastic is placed around the mould at the top.
- The plastic is then blown I not the shape using compressed air.
- Plastic cools on contact with mould surface. The mould is reopened and shape ejected.
What plastics are used in blow moulding?
Low density polythene
What are the advantages of blow moulding?
Accuracy Repeatability Smooth Surface Finish Hollow Products (with hole) One piece construction- don't have to join parts together
What are the identifying features of blow moulding?
Hollow product with an opening at the top
Mould separation lines almost any type of bottle
Uniform wall thickness
Webs for strength
What are the steps to rotational moulding?
- Mould is filled with plastic powder and heated
- The mould is rotated allowing plastic to be distributed over the hot mould surface
- Mould surface is cooled and plastic retains the shape of the mould. Product is removed.
What plastics are used in rotational moulding?
Polypropylene
Polystyrene
Name 4 advantages to rotational moulding
Symmetrical designs can be formed Complex one piece mouldings Tough rigid shapes Lightweight products Quality assured- repeatability No weak areas due to consistent thickness Good quality surface finish/ texture Relatively cost effective- hollow therefore less material used
What are the identifying features of rotational moulding?
Excellent surface detail
No sharp concave sections/corners
Uniform wall thickness
Hollow products (with no opening)
What is 3D printing used to create?
Prototypes out of plastic.
How are models made using a 3D printer
They are made using CAD software and then printed
What are 3D printed models used for?
Testing and advertising before mass manufacturing starts
What forms of plastic can be used in bending?
Sheets
Tubes
How would you bend plastic in a certain part/line
Line bender
How would you bend/form a whole piece of plastic?
The plastic would be heated in an oven.
What is laser cutting used to create?
It can be used to cut or engrave sheets of plastic
You can use these [plastic pieces to create 3D or 2D shapes.
