Addition Polymers

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Addition polymers are synthetically produced by adding together unsaturated monomers without the elimination of any atoms.

Addition Polymerisation

Initiator molecule breaks C=C in alkenes (addition reaction). The new substance is a monomer radical, i.e. has one free electron.
The monomer radical breaks the C=C in another monomer and bonds to it. This, in turn, creates leaves an un-bonded electron across the broken double-bond.
The polymer propagates in this repeating fashion until an inhibitor molecule bonds to the end of a chain, de-radicalising the polymer and preventing it from further elongating.

Monomers	Polymer Structure
Ethylene	Polyethylene (PE)
Vinyl chloride (chloroethene)	Polyvinyl chloride (PVC)
Styrene (ethenylbenzene)	Polystyrene (PS)
Tetrafluoroethylene (tetrafluoroethene)	Polytetrafluroethylene (PTFE)

Polymer	Properties	Uses
Polyethylene Low Density – Branched chains; cannot pack closely together.	Thermoplastic Flexible Low melting point (~80 °C) Lightweight Waterproof	Plastic bags Squeezy sauce bottles Vacuum cleaner tube Water bottles Prosthetics
Polyethylene High Density – Unbranched, linear chains; packs tightly.	Thermoplastic Harder/more rigide than LDPE; less flexible	Freezer bags Cutting boards Garbage bins and buckets
Polyvinyl chloride Standard	Thermoplastic Very hard Rigid Brittle	Piping, sliding, gutters Credit cards Waste water pipes
Polyvinyl chloride Flexible	Flexible Flame retardant Resistant to chemical corrosion	Raincoats Shower curtains Electrical wire insulation
Polystyrene	Stiff Brittle Transparent Can be expanded to form styrofoam (low density insulator)	CD and packaging Plastic wine glasses Floatation devices Shock-absorbent packaging Foam coffee cups
Polytetrafluoroethylene	Hard Rigid High melting point (327 °C) High chemical resistance Low coefficient of friction	Non-stick coating for cooking pans Anti-corrision container, pipe and medical coatings Sliding applications, e.g. bearings.

Polymer	Properties
Polyethylene	LDPE has a high degree of branching, which means is has a low degree of crystallinity and relatively weak dispersion forces. It therefore has a low melting point, is low density and flexible. HDPE has a low degree of branching, so a high degree of crystallinity and stronger dispersion forces. This gives it a high melting point, high density and rigidity.
Polyvinyl chloride	The bulky chlorine side group increases dispersion forces and physical flexibility, resulting in hardness and rigidity. Plasticisers may be added along with PVC chains to increase flexibility by weakening the dispersion forces.
Polystyrene	Bulky benzene substituent increases physical rigidity and strength due to increased dispersion forces.
Polytetrafluoroethylene	Fluorine side groups repel, locking the polymer into a linear, elongated helix. Chains align closely to form a crystalline structure, making PTFE hard and rigid due to dispersion forces.