AQA ------ Materials and their working properties Flashcards
- Papers and Boards - Timbers - Metals and Alloys - Polymers
What are papers and boards made from?
Natural fibres (cellulose) usually from wood.
What is paper weighed in?
GSM (Grams per Square Metre)
When would their be a need for bleached pulp?
For the use of high quality ‘bright’ paper
What are the 3 stages of paper and board production?
1 - Pulping
2 - Sizing
3 - Calendering (Draining +Rolling)
How is pulp created?
- Natural cellulose fibres are mixed with water.
- The mixture is cooked which produces a fibrous liquid known as pulp.
- It is spread onto a mesh conveyor which gets rid of excess water.
What is a Micron?
A unit to measure board thickness, 1000 microns is equal to 1 mm thickness.
What are the 2 categories of natural wood?
- Hardwood
- Softwood
What is ‘felling’ a tree?
A tree is ‘felled’ when it is cut down.
Which trees do Hardwood come from?
Coniferous trees
Which trees do Softwood come from?
Deciduous trees
Why are softwoods good for paper production?
- Softwood trees grow faster than Hardwood.
- Coniferous trees are usually evergreen.
- Hardwood is more expensive.
What are the 4 working properties?
- Strength
- Toughness
- Elasticity
- Hadness
What are manufactured boards?
usually sheets of processed natural timber waste or sawdust combined with adhesives
What are manufactured boards?
usually sheets of processed natural timber waste or sawdust combined with adhesives
What is Ore?
A type of rock which contains a pure metal in small quantities.
How is metal extracted from ore?
- (Ore is obtained from mining)
- The metal is then extracted using a large furnace
- The heat of the furnace separates the metal from the ore and it is drown off as a molten liquid.
What are the 3 categories metals are put into?
- Ferrous
- Non-Ferrous
- Alloys
How is metal extracted from oxides?
Heated with carbon to extract the metals.
How is metal extracted from ore?
- (Ore is obtained from mining)
- The metal is then extracted using a large furnace
- The heat of the furnace separates the metal from the ore and it is drown off as a molten liquid.
What are the properties of a ductile metal?
+ Will stretch without being damaged.
+ Can be stretched or drawn out into long wires.
What are the properties of a malleable metal?
+ Can be hammered into shape without breaking
+ Can be rolled or pressed into sheets
- Will deform under compression
Which element is found in only Ferrous metals?
Iron, (Fe)
Which metals can corrode (rust)?
Iron (Fe) and Steel
Which type of metals are mostly magnetic?
Ferrous
What is the definition of Toughness?
A materials ability to absorb energy and withstand force without cracking or deforming.
What is the definition of Hardness?
A materials ability to withstand abrasion.
What is Tensile strength?
The amount of stretching a material can withstand without breaking or failing.
Which desirable properties are possessed by non-ferrous metals
- Lightweight
- Good conductivity
- Ductile and malleable
- Resistant to corrosion
What is galvanising?
Adding a protective coat of zinc to Iron and Steel in order to prevent rusting.
Which metal is a great Electrical and Thermal conductor?
Copper
What is oxidisation?
Causes the surface of the metal to change colour and dull with time.
How can oxidisation be used as a benefit?
Oxidation rarely affects the working properties of the metal and Copper turns a deep turquoise called “Verdigris”
What is Kapoaka?
Working with recycled cans
What are Alloys?
They are a mixture of at least one pure metal and another element.
Around how much plastic is produced annually?
300 million (and rising)
What are the 2 plastic categories?
Thermo-setting
Thermo-forming
What is another name given to thermoforming plastics?
Thermoplastics
What is the main difference between thermoforming and thermosetting plastics
Thermoplastics can be remoulded without the materials properties being damaged, thermosets have strong bonds that don’t split when heated
Molecular structure of thermoforming plastics?
Long chains of loose molecules with no fixed structure or patterns.
Molecular structure of thermoset plastics?
Individual monomers join to form a large polymer.
What are the pro’s of Thermoplastics?
- Repeated heating and remoulding
- A good finish can be created
- They can be recycled
- It has a plastic memory (pro and con)
What are the cons of thermoplastics?
- Not suitable in areas of heat or UV light
- Plastic memory ( Pro and Con)
What are the pros of thermosets?
- Able to withstand high temperatures
- Waterproof (when solid)
- Hard and durable
- Good electrical conductor
What are the cons of thermosets?
- Cannot be remoulded
What is blow moulding used to create?
- Forming hollow plastic items
What is injection moulding?
- When soft plastic is injected into a mould
What is vacuum moulding used to create?
- When a sheet of softened plastic is formed around a mould.
What is extrusion (moulding/forming) used to create?
- Creating objects with a cross section profile
What are the tree types of Polyethylene?
- PETE =Polyeethylene terephthalate
- HDPE = High density Polyethylene
- LDPE = Low density Polyethylene
What is the most common thermoplastic?
Polyethylene
How much Polyethylene is created annually?
over 80 million tonnes per year
