Materials Flashcards
1
Q
What are plastics?
A
A group of materials made up of long chain molecules.
2
Q
Give five reasons why plastics are popular in manufacturing.
A
- Lightweight
- Energy Insulator
- Good strength to weight ratio
- Corrosion resistant
- No need for finishing
3
Q
Give two natural materials that are used to produce semi-synthetic polymers?
A
- Cellulose
- Casein
4
Q
Name the three sources of synthetic plastics.
A
- Coal
- Oil
- Gas
5
Q
Which process is used to produce synthetic plastics?
A
Thermal cracking
6
Q
Give the three types of plastic.
A
- Thermoplastic
- Thermoset
- Elastomer
7
Q
Define a thermoplastic
A
A plastic that can be repeatedly reheated and remoulded.
8
Q
Define a thermoset plastic.
A
A plastic that undergo a chemical change making them permanently rigid.
9
Q
Define an elastomer
A
A plastic that can be distorted and return to its original shape.
10
Q
Name seven thermoplastics
A
- ABS
- Nylon
- PP
- HIPS
- HDPE
- PVC
- PET
11
Q
What does ABS stand for?
A
Acrylonitrile Butadiene Styrene
12
Q
Give three properties of ABS.
A
- High impact strength
- Scratch resistant
- Durable
13
Q
Give three common uses of ABS.
A
- Kitchen products
- Phone cases
- Interior car parts
14
Q
Give two properties of Nylon.
A
- Resistant to wear
- Low coefficient of friction
15
Q
Give three common uses of Nylon.
A
- Bearings
- Gears
- Clothing
16
Q
What does PP stand for?
A
Polypropylene
17
Q
Give three properties of PP.
A
- Food safe
- Durable
- Easily machined
18
Q
Give three common uses of PP.
A
- Food containers
- Medical equipment
- Rope
19
Q
What does HIPS stand for?
A
High Impact Polystyrene
20
Q
Give two properties of HIPS.
A
- Impact resistant
- Lightweight
21
Q
Give two common uses of HIPS.
A
- Toys
- Fridge linings
22
Q
What does HDPE stand for?
A
High Density Polyethylene
23
Q
Give two properties of HDPE.
A
- High density
- High chemical resistance
24
Q
What does PVC stand for?
A
Polyvinyl Chloride
25
Give two properties of PVC.
- High chemical resistance
| - Resistant to weathering
26
Give two common uses of PVC.
- Cable insulation
| - Window frames
27
What does PET stand for?
Polyethylene Terephthalate
28
Name three thermoset plastics.
- Epoxy resin
- Polyester resin
- Urea formaldehyde
29
Give two properties of epoxy.
- High strength when reinforced.
| - Wear and chemical resistant
30
Give two common uses of epoxy.
- Electronic component coverings.
| - Adhesives
31
Give a common use of polyester resin.
-Casting for glass reinforced plastic.
32
Give two common uses of urea formaldehyde
- Electrical fittings
| - Adhesives
33
Give two properties of urea formaldehyde.
- Rigid
| - Electrical insulator
34
What is a filler?
A material used to increase the volume of plastic material making the overall material cheaper.
35
What is flame retardant?
A plastic additive designed to reduce the risk of combustion..
36
Give four examples of fillers.
- Sawdust
- Wood flour
- Crushed quartz
- Limestone
37
How do flame retardant additives work?
Once combustion has started, agents are released that stifle the combustion.
38
What is an anti-static agent?
An additive that prevents static building up on a product.
39
What is a plasticiser?
An additive that improves the flow properties of plastics making them easier to form.
40
What is a stabiliser?
An additive that reduces the effects of UV light.
41
What is a biodegradable plastic?
A plastic designed to breakdown in a biologically rich environment.
42
Give three examples of applications for biodegradable plastics.
- Shopping bags
- Drinks bottles
- Disposable products
43
Give an example of a biodegradable plastic.
Polylactides (PLA)
44
What is Biopol?
A polymer used to make biodegradable packaging.
45
How is Biopol produced?
Bacteria culture
46
What are oxodegradable polymers?
Plastics with additives that promote short degradation times.
47
What three factors will break down oxodegradable polymers?
- Heat
- Oxygen
- Mechanical stress
48
What causes photo-degradable polymers to break down?
UV light
49
What is a van der Waals bond?
A type of atomic bonding found in thermoplastics.
50
What does TPE stand for?
Thermoplastic elastomer
51
Give three uses of TPE.
- Fibre optics
- Overmoulding of grips
- Seals
52
What does LSR stand for?
Liquid silicon rubber
53
What is the main advantage of LSR?
It can maintain its insulating and elastometric characteristics over a wide range of temperatures.
54
Give four examples of materials that can be reformed by heating.
- Clay
- Paper
- Metal
- Glass
55
Give two examples of materials that can't be reformed once heated.
- Cement
| - House bricks
56
What is a composite?
A mixture of two or more different materials.
57
What does FRP stand for?
Fibre-reinforced polymer
58
What is a fibre reinforced polymer?
Composite made by combining a woven material, polymer resin and a catalyst.
59
What is a fibre reinforced composite?
Material made up of resin and fibre.
60
What is a particle-based composite?
Composites that consist solely of particles of two or more materials.
61
Define warping.
Deforming in timber due to uneven drying.
62
Give three materials that are used to produce reinforced polymers.
- Carbon fibre
- Kevlar
- Glass
63
What are the three main groups of composite materials
- Fibre reinforced
- Particle based
- Sheet based
64
Give two advantages of man-made boards.
- Increased stability against warping.
| - Equal strength in all directions.
65
Give four general characteristics of fibre-reinforced composites.
- Good strength to weight ratio.
- Resistant to corrosion.
- Fatigue resistant.
- Low thermal expansion.
66
What is the range of fibreglass gauges used for glass-reinforced plastic?
5μm-30μm
67
Give three examples of particle-based composites.
- Cements
- Concretes
- Tarmac
68
Give two examples of types of cement.
- Tungsten carbide
| - Titanium carbide
69
Give four examples of fibre-reinforced composites.
- Natural woods
- Polymers mixed with fibres
- Elastomers mixed with fibres
- Concretes mixed with fibres
70
Give three examples of fibre-reinforced polymers.
- GRP
- Plastic laminates
- Carbon fibre
71
Give four examples of man-made sheet-based composites.
- Plywood
- MDF
- Hardboard
- Chipboard
72
Give two common uses of plywood.
- Panelling
| - Furniture backs
73
Give two common uses of chipboard.
- Knockdown furniture
| - Kitchen worktops
74
What is Kevlar?
A composite made from aromatic and aramid molecules.
75
How are Kevlar fibres arranged?
The fibres are woven into a cloth.
76
Explain how Kevlar functions as protection.
All the horizontal and vertical fibres absorb some of the force of an impact.
77
Give five common uses of Kevlar.
- Body protection
- Sports equipment
- Sails for windsurfing
- Run-flat tyres
- Gloves
78
Give seven properties of Kevlar.
- High strength to weight ratio.
- Low electrical conductivity.
- High chemical resistance.
- High toughness.
- High cut resistance.
- Flame resistant.
- Self-extinguishing.
79
Give two common uses of GRP.
- Vehicle bodies
| - Boat hulls
80
Give three common uses of carbon fibre.
- Bike frames
- Artificial limbs
- Car bodywork
81
Give two common uses of plastic laminates.
- Gears
| - Work surfaces
82
What type of loads is concrete good for?
Compressive loads.
83
What type of loads is concrete vulnerable to?
Tension
84
Give four general characteristics of particle-based composites.
- High strength in compression.
- Low strength in tension.
- Good stability
- Uniform structure
85
What determines the characteristics of a concrete material?
The ratio of constituent parts
86
Give five advantages of concrete.
- Can be moulded into complex shapes.
- Properties similar to stone.
- Components readily extracted.
- Can be cast in situ.
- High strength in compression.
87
Give a disadvantage of concrete.
Poor strength in tension.
88
What is a cermet?
A mixture of metal and ceramic.
89
Give two advantages of cermets.
- Resistant to high temperatures.
| - Tough and shock resistant.
90
Give a disadvantage of cermets.
Hard to process
91
What is ALU composite made of?
- 0.3mm aluminium sheet
| - Polyethylene core
92
Give two advantages of using ALU.
- Vibration dampening
| - Thermal insulation
93
Give two advantages of using tungsten carbide on a cutting edge.
- More durable
| - Reduced necessity for re-sharpening
94
Give a disadvantage of using tungsten carbide on a cutting edge.
The blade can cut through the materials beneath the food.
95
Give two advantages of chipboard flooring.
- Large areas can be covered with one sheet.
| - Cost is reduced
96
Give a disadvantage of chipboard flooring.
Chipboard flooring has to be covered.
97
What is a monocoque?
Single-piece shell frame
98
What is a ferrous metal?
A metal that contains iron and carbon.
99
What is a non-ferrous metal?
A metal that doesn't contain iron.
100
What is a ferrous alloy?
A mixture of two or more metals with at least one containing iron.
101
What are the three main groups of metals?
- Ferrous metals
- Non-ferrous metals
- Alloys
102
Give two examples of types of steel.
- Mild steel
| - High carbon steel
103
Give five examples of non-ferrous metals.
- Aluminium
- Copper
- Lead
- Tin
- Zinc
104
Give three examples of ferrous alloys.
- Stainless steel
- High speed steel
- Die steel
105
Give three examples of non-ferrous alloys.
- Brass
- Bronze
- Duralumin
106
What is the only metal found in a usable form?
Gold
107
Give two iron ores.
- Magnetite
| - Haematite
108
What percentage of Earth's crust is made up of metal ores?
25%
109
What is the most common ore in Earth's crust?
Aluminium ore
110
How is iron extracted from its ore?
Using a blast furnace.
111
Give three effects of adding carbon to iron.
- The material becomes harder.
- Toughness is reduced.
- The material can be heat treated to increase strength and hardness.
112
How much carbon will low carbon steel contain?
<0.3%
113
How much carbon will high carbon steel contain?
0.3-1.7%
114
How much carbon will low carbon cast iron contain?
3.5%
115
What is the most ductile steel?
Low carbon (mild) steel
116
What is the most hard steel?
Cast iron
117
What is the most tough steel?
Low carbon steel
118
Give three common uses of mild steel.
- Nuts & bolts
- Car bodies
- White good panels
119
Give two common uses of medium carbon steel.
- Springs
| - Gardening tools
120
Give two common uses of high carbon steel.
- Hand tools
| - Hole punches
121
Give two common uses of cast iron.
- Brake discs
| - Engines
122
What is the melting point of aluminium?
660°C
123
What is the melting point of copper?
1083°C
124
What is the melting point of gold?
1063°C
125
What is the melting point of lead?
330°C
126
Give two common uses of aluminium.
- Kitchenware
| - Overhead power cables
127
Give three common uses of copper.
- Electrical contacts and wiring
- Domestic piping
- Jewellery
128
Give two common uses of gold.
- Jewellery
| - Electronics
129
Give a common use of lead
Roofing
130
Give two common uses of platinum.
- Jewellery
| - Thermocouple cables
131
Give two common uses of silver.
- Luxury kitchenware
| - Processing photographic film
132
Give two common uses of tin.
- Food wrapping foil
| - Coating for cans
133
Give two common uses of titanium.
- Surgical tools
| - Joint replacements
134
Give three common uses of zinc.
- Galvanised steel
- Lock mechanisms
- Small gears
135
Give a common use of duralumin.
Structural components for aircraft
136
Give two common uses of brass.
- Cast valves
| - Boat fittings
137
Give two common uses of bronze.
- Coins
| - Bearings
138
Give a common use of nitinol.
Smart metal alloys
139
Give six potential advantages of alloying metals.
- Change of melting point.
- Change of colour.
- Increase in strength, hardness and ductility.
- Enhanced resistance to corrosion.
- Change of thermoelectric properties.
- Improves flow properties.
140
Which three elements is steel alloyed with to give stainless steel?
- Chromium
- Nickel
- Magnesium
141
Which three elements is steel alloyed with to give high speed steel?
- Tungsten
- Chromium
- Vanadium
142
Which three elements is steel alloyed with to give die-steels?
- Chromium
| - Manganese
143
Which three elements is steel alloyed with to give high tensile steels?
Nickel
144
Give a characteristic of steel.
Corrosion resistant
145
Give a characteristic of high speed steel.
Very hard
146
Give a characteristic of die-steels.
Wear-resistant
147
Give a characteristic of high tensile steels.
Good tensile strength
148
Give a common use of stainless steel.
Cutlery
149
Give a common use of high speed steel.
Cutting tools
150
Give a common use of die-steels.
Fine press tools
151
Give a common use of high tensile steels.
Car engine components
152
What is work hardening?
The effect of cold working a metal that causes the crystal structure to distort.
153
What is duralumin?
An alloy containing aluminium
154
What is a hardwood?
A timber that is deciduous and slow growing.
155
What is a softwood?
A timber that is evergreen and quick growing.
156
Define deciduous.
A tree that loses its leaves in autumn.
157
Define evergreen.
A tree that doesn't lose its leaves.
158
Give four examples of hardwood.
- Oak
- Ash
- Beech
- Walnut
159
Give three examples of softwood.
- Pine
- Spruce
- Fir
160
In what direction does wood have the greatest strength?
In the direction of the fibres.
161
What is a wood knot?
A defect where a branch has started to grow.
162
What is wood conversion?
Sawing up logs to give usable wood forms.
163
What is slab sawing?
A form of conversion where the trunk of the tree is cut into slabs.
164
What is quarter sawing?
A form of conversion that can prevent warping and can be used to enhance the grain.
165
When do splits occur in wood?
When the wood is drying.
166
What causes shrinkage?
Moisture lost in seasoning
167
What causes twisting in wood?
A combination of a method of conversion and uneven seasoning.
168
What is wood rot?
the breaking down of lignin resins in in woods that hold the tracheids together.
169
What is a deathwatch beetle?
An insect responsible for the destruction of hardwoods.
170
What is kiln drying?
A form of seasoning that uses steam in a controlled way to reduce the content of moisture in timber.
171
Give three benefits of seasoning wood.
- Increases the strength and stability.
- Reduces corrosion in surrounding metalwork.
- Makes timber less prone to rot.
172
What is a green timber?
A timber that hasn't been thoroughly seasoned.
173
Give three uses of green timber.
- Chairs
- Fencing
- One off structures
174
What is a veneer?
A thin section sheet of timber that is glued to a cheaper base material.
175
Give five examples of hardwoods suitable for veneers.
- Beech
- Oak
- Ash
- Walnut
- Yew
176
What is the general thickness of paper backed veneers?
0.8mm
177
Give two advantages of paper backed veneers.
- The veneer is unlikely to split.
| - The paper prevents glue from seeping through to the surface.
178
What is a laminate?
A material that is made up of layers.
179
Give two examples of laminates.
- Kitchen surfaces
| - Laminate flooring
180
What are the four layers of laminate flooring?
- Melamine layer
- High density fibreboard
- Printed layer
- Resin based overlay
181
What is plywood made from?
Layers of hardwood veneers bonded together at 90°.
182
Give six examples of man-made wood composite boards.
- Plywood
- Block board
- Chipboard
- MDF
- Hardboard
- Sterling board
183
What is block board made from?
Strips of wood bonded together with a veneered surface.
184
What is chipboard made from?
Fine chips mixed with resins.
185
What is MDF made from?
Fine wood fibres mixed with resins.
186
What is hardboard made from?
Fine wood fibres mixed with resins and impregnated with oil.
187
What is sterling board made from?
Wood shavings compressed into resins.
188
Give two examples of how IKEA ensures its products are sustainable.
- They source timber from managed forests.
| - They use timbers that are fast growing.
189
Give two common uses of lime-soda glass.
- Windowpanes
| - Storage glass
190
What is float glass?
Sheet glass produced by floating molten glass on a bath of molten tin.
191
What is plate glass?
A glass with few impurities that is rolled and polished.
192
What is cullet?
Glass that has been crushed into small particles ready for recycling.
193
How is lime-soda glass produced?
A mixture of sand, lime and sodium carbonate is heated to 1500°C in a furnace.
194
What type of force is glass vulnerable to?
Mechanical shock
195
Give a benefit of using lead glass.
It has a greater ability to reflect light.
196
Give two benefits of using boro-silicate glass.
- High heat resistance
| - Chemical resistant
197
How is laminated glass produced?
Two thin sheets of glass sandwich a tough polymer.
198
How does self-cleaning glass work?
- A hydrophobic coating is applied to the outside.
| - The material interacts with UV light to break down dirt which is washed away by rain.
199
Give five advantages of using polymers over glass.
- Lightweight
- Low melting point
- Impervious to gases
- Can be squashed without breaking.
- Screw tops can be used.
200
Give five advantages of using glass over polymers.
- More rigid
- Scratch resistant
- Greater clarity of light
- Heat resistant
- Gives a sense of quality
201
Give two disadvantages of using glass.
- Heavy
| - High melting point
202
What is fine bone china?
A form of clay containing ground animal bone.
203
What is slip?
Liquid clay
204
Give two common uses of alumina.
- Spark plugs
| - Cutting tools
205
Give a common use of beryllia.
Nuclear reactor crucibles
206
Give a common use of magnesia.
Furnace lining
207
Give a common use of zirconia.
Rocket lining
208
Give two useful properties of ceramics.
- Heat resistant
| - Resistant to erosion.
209
What is a rendering?
Colour drawings using tones and texture to produce a realistic impression of designs.
210
What are the three main textures available in watercolour papers?
- Hot pressed: hard, smooth
- Cold pressed: rough
- Extra rough with more peaks and troughs.
211
What is the purpose of bleed proof paper?
Prevent ink seeping through sheets.
212
What does the term gloss refer to?
Surface lustre
213
What does the term glare refer to?
Reflective nature of the paper
214
What does the term finish refer to?
General surface characteristics
215
What does the term smoothness refer to?
The absence of surface irregularities
216
Give four factors that determine paper strength.
- Strength of individual fibres.
- Length of fibres
- Strength of bonds between fibres.
- Structure of the paper
217
What is foam board?
A multi-layer board made with two outer layers of card.
218
Give three properties of foam board.
- Lightweight
- Easily cut
- Difficult to bend
219
How are correx boards produced?
Extruding a thermoplastic to produce a sheet material.
220
What is a smart material?
Materials whose physical properties change in response to an input.
221
What is a modern material?
A material that has only been available in its current form since the 70s.
222
What is a piezoelectric device?
- Devices that generate electricity when loaded.
| - Devices that change shape when connected to an electrical circuit.
223
What is thermochromic pigment?
A smart material that changes colour in response to changes in temperature.
224
What are liquid crystals?
Carbon based crystals that can have their orientation changed when an electric current is passed through them.
225
How do battery test strips work?
The strip contains a thermochromic ink that heats up as a current passes through. If there is sufficient current, the strip will change colour.
226
What are phosphorescent pigments?
Ceramic powders that have the ability to absorb light and then release the energy over a long period of time.
227
What are shape memory alloys?
Metal alloys designed to remember their shape under specific conditions.
228
Give an example of a shape memory alloy.
Nitinol
229
Give three common uses of shape memory alloys.
- Plating broken bones
- Secure electrical connectors
- Memoflex glasses
230
How can the piezoelectric effect be achieved?
Applying an input to a quartz crystal.
231
Explain how piezoelectric sensors work.
- The charge produced by a crystal is proportional to the force applied.
- A signal can be produced giving an indication of the load being applied.
232
What is smart grease?
A material that controls how quickly two components can slide over each other.
233
Give three uses of smart grease.
- Retractable cup holders
- Steering mechanisms
- Anti-vibration mechanisms
234
Define rheological
The way greases and fluids react to the movement between adjacent components.
235
What is a smart fluid?
A fluid that changes from a liquid into a solid when shaken or stirred and then returns when the movement stops.
236
What is electroluminescent wire?
A cable containing a conductor coated with phosphor and a conductor coated with semi-conductor material.
237
When does electroluminescent wire glow?
When an a.c. current passes across the conductors.
238
How do glowsticks work?
A chemical reaction between two liquids releases light energy.
239
What is a quantum tunnelling composite?
Metal filled polymers that can change their conductive properties when deformed
240
What is electronic smart glass?
A glass that can change from transparent to opaque when a voltage is applied.
241
What are the three main types of electronic smart glass?
- LCD
- Electrochromic glass
- Suspended particle glass
242
How do fibre-optic cables transmit data?
By transmitting light as a series of pulses.
243
Give an advantage of using fibre optic over copper cable.
Greater quantities of information can be transferred simultaneously.
244
Give two advantages of using engineering timbers.
- Beams can be made to fit the customer's requirements.
| - Waste timber is reduced
245
What is plastic coating?
The process of heating a metal and then dipping it in fluidised thermoplastic giving a smooth finish.
246
What two materials are usually used for plastic coating?
- PET
| - PP
247
Give an advantage of foaming a material.
Foams can disperse the energy of an impact.
248
What is the main characteristic of titanium?
High strength to weight ratio
249
What is polymorph?
A low melting point polymer used for prototyping.
250
What temperature does polymorph soften at?
60°C
251
What is PMC?
Precious metal clay
252
What is PMC often used for?
Bespoke jewellery
253
What are microfibres?
Fine polymer based fibres
254
Give an advantage of using microfibres for waterproof clothing.
Water vapour can pass out but water droplets are unable to pass in.
255
What is micro-encapsulation?
Containing chemicals within microfibres.
256
What is a PCM?
Phase change material
257
What is the main purpose of PCMs?
Controlling body temperature
258
How do PCMs work?
The material absorbs body heat while exercising then releases the heat when the user rests.
259
What is dichroic glass?
A material that can reflect different wavelengths of light.
260
Give three common uses of dichroic glass.
- Reflective surfaces for satellites
- Laser mirrors
- Jewellery manufacture
261
What determines the colour of light reflected by dichroic glass?
The metal oxide layers used in the glass.
262
How is flexible MDF produced?
Grooves are made in the material.
263
How is flexible plywood produced?
- The material is made from only three layers.
| - The two outer layers are an open grained timber and are much thicker than the inner core.
264
What is aeroply?
A thin section of high quality plywood used for constructing gliders.
265
What is Maplex?
A material like MDF without the toxic resins binding the fibres.
266
What is Hexaboard?
An exterior quality plywood with a hard phelonic resin laminated surface embossed with hexagonal patterns.
267
Give a common use of hexaboard.
Flooring
268
How are the fibres in Maplex bonded?
Using high compressive forces
269
What is rust?
The oxidation of ferrous metals due to contact with moisture.
270
What is electrochemical corrosion?
When two materials are joined and acidic rainwater forms an electrochemical cell causing corrosion in the materials.
271
Why is electrochemical corrosion slow?
The voltage and current are very small.
272
What are the three main causes of decay in wood?
- Wet rot
- Dry rot
- Attack by insects
273
What is wet rot?
Decay in wood caused by alternating cycles of the timber being wet then drying.
274
What is dry rot?
A fungal attack that breaks down the structure of the wood.
275
What is woodworm?
An insect that attacks hard and soft wood by laying eggs in crevices leaving the larvae to eat eat its way out of the timber.
276
What is the main cause of degradation in plastics?
UV radiation
277
Give five potential purposes of an applied finish.
- Protecting the material from corrosion.
- Making the product water repellent.
- Improved resistance to wear and fatigue.
- Improved ability to reflect or absorb heat.
- Improved ability to insulate energy.
278
What is a self-finishing material?
A material that has an acceptable finish after processing.
279
What is a self-coloured material?
A material that has an acceptable colour after processing.
280
What is an applied finish?
The coatings applied to the surface of a material.
281
What is a burr?
A rough edge created by a cutting process.
282
What is deburring?
The process of removing burrs from the edge of a material.
283
What is a varnish?
A hard transparent finish that is applied to wood.
284
What is a natural barrier?
Protective layers close to the surface of a material.
285
Give an example of a natural barrier.
Oxide layer found on metals
286
What is blueing?
A method of finishing steel that involves heating the product then quenching in oil.
287
Give five methods of applying barriers to metals.
- Electroplating
- Dipping
- Spraying
- Brushing
- Rolling
288
What is electroplating?
The use of electrolysis to coat a base metal with a second, more decorative metal.
289
What is anodising?
An electrochemical process used to make the surface of aluminium more durable.
290
What is enamelling?
The process of spraying ground glass onto metal.
291
Give two methods of applying a titanium coating.
- Physical vapour deposition.
| - Plasma spraying
292
What is powder coating?
Using an electrostatic charge to coat a metal product.
293
What is plastic dip coating?
Finishing a metal based component by dipping the material into melted polymer.
294
What are the four main groups of wood preservatives?
- Tar oil derivatives
- Water soluble
- Organic solvent
- Tanalising
295
What is a wood preservative?
A treatment that prevents moisture entering the structure of the material.
296
What is tanalising?
A process whereby wood is pressure treated with preservative.
297
What is PMMA commonly known as?
Acrylic
298
Which polymer is applied to lenses to prevent scratching?
CR39
299
Give three compounds that are used for anti-reflective coatings.
- Silicon dioxide
- Aluminium oxide
- Zirconium dioxide
300
What generally determines the properties of a material?
The material's structure
301
Give four functional requirements of the material for a soft drinks can.
- Must not be affected by acids.
- Must not contaminate drinks.
- Must have strength to withstand internal pressure.
- Must be formable into the desired shape.
302
Give three functional requirements of the material for an electric plug casing.
- Acts as an electrical insulator.
- Can withstand heat generated by current.
- Sufficiently rigid and durable to withstand insertion and removal from a socket.
303
Define plasticity.
The ability of a material to be permanently changed in shape by external forces.
304
Define malleability.
The ability of a material to withstand deformation by compression.
305
Define ductility.
The ability of a material to be drawn out.
306
Define elasticity.
The ability of a material to flex when forces are applied and regain normal shape afterwards.
307
Define toughness.
The ability of a material to withstand a sudden impact without fracture.
308
Define hardness.
The ability of a material to resist abrasive wear and indentation.
309
Define durability.
The ability of a material to withstand corrosion and deterioration.
310
Define stability.
The ability of a material to resist changes due to its environment.
311
Define strength.
The ability of a material to withstand force without breaking or permanently bending.
312
Define tensile strength.
The ability of a material to resist stretching or pulling forces.
313
Define compressive strength.
The ability of a material to withstand pushing forces.
314
Define bending strength.
The ability of a material to withstand forces that attempt to bend the material.
315
Define shear strength.
The ability of a material to resist sliding forces acting against each other.
316
Define torsional strength.
The ability of a material to withstand twisting forces.
317
Define fusibility.
The ability of a material to change to a liquid when heated.
318
Define density.
Mass per unit of volume
319
Define electrical conductivity.
The ease with which electrons can pass through a material.
320
What is a semi-conductor?
A material that only allows current to flow under certain conditions.
321
What is thermal conductivity?
The ease with which heat travels through the material.
322
Define opaque.
Does not allow light to pass through.
323
Define translucent.
Allows some light to pass through
324
Define transparent.
Allows light to pass through.
325
Give two methods of testing for hardness.
- A file can be run over the material.
| - A dot punch is used to create an indent.
326
Give a method of testing ductility.
Placing the material in a vice and attempting to create a right angle bend.
327
Give a method of testing tensile strength.
Placing samples in a vice and applying loads to them.
328
Give a method of testing toughness.
Striking with a hammer.
