Chapter 9 Flashcards
Polymers
Are long chains of monomers
Monomers
Are the things that link together to form polymers
Polymerisation
The process in which the monomers link together
Copolymers
When two different monomers link together
Thermosoftening
Can be heated repeatedly, softened, reshaped and hardened by cooling.
Thermosetting
do not soften when heated but char instead. They cannot be reshaped.
Addition polymerisation
The monomers have a double bond between two carbon atoms. This double bond breaks to allow the long chains to form.
Isotacic branching
side branches are arranged on the same side of a linear polymer
produces rigid, hard polymers because dispersion forces act stronger because they can packed closely together with high mp/bp
ie; buckets, milk crates
Atactic branching
branches occur at irregular points on both sides of the chain
molecules cannot get as close together and a low-density substance is formed
Crosslinking
Small amounts of crosslinking cause an elastomer
Large amounts of crosslinking cause a thermosetting polymer because there is 3D crosslinking
How are crosslinks made?
Heating the material after the polymer chains have been formed
Adding another substance that reacts with the atoms on the chain, joining them together
Degree of crystillinaty
Crystalline are packed into regular lines, creates a hard, strong and opaque structures
Amphorus are packed irreguarly, more easily deformed, transparent
Length of polymer chains
As chain length increases mp/bp increases as larger chains are more likely to get tangled and dispersion forces increase
Addition of plasticisers
Added to polymers which cause more space between polymers and result in softer more flexible polymers
Additives
UV stabilisers, absorb UV to prevent the polymer breaking down
Flame retardants to reduce the burning tendency
Dyes to add colours or patterns
