Materials and their properties Flashcards
(27 cards)
What needs to be known to specify a metal
Chemical composition Surface Treatment Production and finishing method Supply form (sheet, tube..) Quality Control standards
What carbon content is Wrought iron
Up to 0.008%
What carbon content is cast iron
Above 2%
What type of iron is used for general engineering applications and what is its carbon content
Very low carbon
up to 0.05%
What must stainless steel contain
10.5% chromium, silicon or manganese
What are the 3 steel groups
Austenitic
Martensitic
Ferritic
What is brass defined ass
An alloy of copper and another element
What are some good general properties of copper based metal
Good electrical and thermal conductors
Weak
Easy to work
Good wear characteristics
What are some properties of magnesium
Light
Very low tensile strength
Very easy to mould
What are sources of plant based polymers
Cellulose
Tree resins
Starches
How do polymer branches effect the performance of a polymer
Side branches create entanglements to prevent deformations
Reduces stress cracking
Reduces density
Are thermosets or thermoplastics Cross linked
Thermosets
How does cross links effect a polymer
Makes the polymer harder, stronger, stiffer, more brittle and more dimensionally stable
What is a homopolymer
All the mers are the same type
What is a co polymer
2 different types of mer are used
What is a Terpolymer
Contains 3 different mer units
Are branched or linear polymers more crystalline
Linear
How does crystallinity Effect material properties
Stiffer, harder, denser, more resistant to heat and solvents.
Reduces ductility or transparency
What material properties are effected by molecular weight
Tensile strength
Impact strength
Resistance to cracking
Viscosity when molten
What is the degree of polymerisation
Ratio between molecular weight of polymer and molecular weight of repeating unit
Polymers with a high degree of polymer have a higher……
Viscosity
What are the differences between thermosetting plastics and thermoplastics
Thermosets have stronger bonds and will not melt they will just burn eventually, during heating the hardness and strength is unchanged
Thermoplastics have weaker bonds and will undergo melt or glass transition upon heating
What materials are often used as additives to plastics
plasticisers Carbon black Antioxidants Fillers Colourants Flame retardants Lubricants
What is material is most commonly added to reinforce polymers
Glass fibres
