Polymers Flashcards
Best polymer properties (3)
Cheap, Lightweight, corrosion resistance
Difference between Engineering polymers and common
Improved strength and temp performance
What are polymers?
Repeat units of a molecular unit
2 Ways of creating polymers
Addition polymerisation, condensation polymerisation
Addition polymerisation what
Monomers are joined together with no extra product created
Condensation Polymerisation
To molecules are added together
Does condensation polymerisation result in an additional product
yes a condensate (water, methane)
How to measure polymer size(2)
Molecular weight or degree of polymerisation
How to calculate degree of polymerisation?
number of monomers
Polymer chains- Linear
just straight
Polymer chains- branched, properties
like tree, lower density and strength
Polymer Chains- crosslinked (properties)
covalent bonds- increases strength and stiffness
What is a copolymer?
2 or more types of polymer
grafted copolymer what
linear with one monomer and branches of the other sticking out
Block copolymers what
many of one monomer and then many of the other
Thermoplastics- structure
linear/ branched
Thermoplastics- tensile properties (4) and why?
plastic and ductile, not strong low density cause chains can be pulled apart from each other
Thermoplastics- heat?
Soften and melt
Thermoplastics- crystal
mix of amorphous and crystalline
Thermoplastics- examples
Polyester, polycarbonate, polyethylene
Thermoplastics - stress strain curve why weird
Stress reduces after elastic region
Why does stress strain curve weird
Cause the chains slide rotate disentangle and become aligned with stress direction
Thermoplastics temperature dependence
Can be glassy leathery or viscous depending on temp
Thermoplastics- creep- describe
under constant load sample gradually gets longer
Thermoplastics - relaxation describe
under constant strain leads to stress reaction- exponential- depending on temp
Thermosetting- chains?
Cross-linked
Thermosetting- heat?
do no soften
Thermosetting- properties (3)
Harder, more brittle and more stable
Elastomers- chains
Crosslinked but specially
Elastomers- deformation
no plastic deformation but still has viscoelastic relaxation
Thermoplastics - blow moulding
using air to get into shape
Thermoplastics- calendaring
Like making pasta
Thermoplastics- thermoprocessing
using a vacuum to suck it to the right bits
Thermoplastics-injection moulding
Injecting plastics into mould
Thermosets- processing general
must be processed and a liquid before cross-linking
Thermosets- compression moulding
using hot dies to shape and start crosslinking
Thermosets- transfer moulding
put in mould and then it will polymerize through heat
Are thermoplastics recyclable
yes but not easy as have to be pure and get rid of extras
Are thermosets recyclable
no
