Polymeric Materials Flashcards
What are polymers
– Very large molecules
– low density, light weight materials
– may be extremely flexible
– synthetic and natural materials
What type of bond to polymers have
Covalent Bond • electrons are shared between adjacent atoms, each contributing at least one electron • shared electrons belong to both atoms • directional bond means resulting molecules have specific shapes
Polymer Definition
A long 1D chain molecule of covalently bonded repeat units
Or a 3D network of covalently bonded repeat units
Advantages of Polymer Characteristics
Easy Processing, High Ductility, Light Products, Thermal Insulators, Electrical Insulators, High Corrosion Resistance
What atoms is a polymer chain made up of
Carbon and Hydrogen
What is a monomer
Small, unreacted single molecule for polymer
What is a mer
single repeat unit of a polymer
Polymer = entire polymer chain
What is polymerisation
When monomer molecules react together to form polymer chains
Degree of polymerisation formula??
n= (number of mer units) / (polymer molecule)
Increasing a polymer chain length creates?
A stronger material, increased stiffness, higher melting point
What is a linear chain polymer
a polymer consisting of a single continuous chain of repeat units
What is a branched chain polymer
a polymer that includes side chains of repeat units connecting onto the main chain of repeat units
What is a hyper branched chain polymer
a polymer consisting of a constitutional repeating unit including a branching groups
What is a cross linked polymer
a polymer that includes interconnections between chains
What is a net work polymer
a cross linked polymer that includes numerous interconnections between chains
What are the three classes/groups of polymers
Thermoplastics, Thermosets, Elastomers/Rubbers
What is the chain structure of a thermoplastic like?
Long chains with very limited or no cross-linking which behave in a plastic ductile manner
Examples of Thermoplastic materials
Nylon, polyethylene, polystyrene, PVC
What does POLY MER stand for?
Many Units
What is the chain structure of a thermoset?
Highly cross-linked, 3D network structures
Thermoset mechanical properties?
Birttle, decompose when heated
Examples of Thermoset materials
urethane, epoxy, polyester,
and silicone
Elastomers and rubbers chain structure
Light cross-linking, allowing the material to return to its original shape without plastic deformation
What is a homopolymer
A polymer consisting of only one type of constitutional repeating unit
What is a copolymer
A polymer consisting of two or more constitutional repeating units (A-B )
What is a Polymer Crystal
Ordered atomic arrangements involving molecular chains
Polymers can be crystalline
Can a polymer be completely Crystalline?
No
Max percentage of polymer degree of crystallinity?
95% (HDPE)
What two compositions make up a polymer structure diagram?
Amorphous regions & Crystalline regions
affects of increasing the crystallinity of a polymer
increase the strength and rigidity of the polymer
2+2=4, -1 =3
Quick Maths
How can plastics be formed?
Injection moulding (thermoplastics and some thermoset) Extrusion Blow Moulding Extrusion Blow Moulding Injection Blow Moulding Compression and transfer moulding
