Polymers Flashcards
What is thermoplastic?
Substance moulded using heat and pressure that retains shape when cooled
What is thermosetting?
Cannot be softened by heat once set
Polymerisation?
Monomers link together to form polymers
What are copolymers?
Formed when two or more monomers are used
Addition polymerisation?
Monomer must have double bond; double bond breaks to form long chain
Linear polymers?
Main backbone is unbranched, eg CH3 is a side branch
What can side branches affect?
The way they are arranged can determine different properties
Isotactic?
When side branches are on same side of chain.
Greater dispersion forces so polymer lacks together closely. High density, rigid and tough.
Atactic?
Side branches in chain are irregular.
Cannot pack closely together = low density substance
LDPE
Low density polyethene
Large number of atactic side branches.
HDPE
High density polyethene.
Few side branches are formed, and dispersion forces act more efficiently. Structure is packed together forming high density.
Cross links
Bonding between two chains.
Thermosetting polymers
Condensation polymerisation
Uses monomers that have two functional groups per molecule.
Head to tail join, while a small molecule (water) is lost.
What is a polymer?
Large molecules made by joining monomers together
