Ch 9 - Polymers Flashcards
What is a polymer?
Large molecules made by joining smaller molecules called monomers in a polymerisation reaction.
What is a monomer>
Simple molecule that is strung together to make polymers
What are copolymers?
Two or more monomers are joined into the polymer
What are thermosoftening polymers?
Polymers that can be repeatdly heated, cooled, moulded and reshaped.eg poly vinyl chloride
What are thermosetting polymers?
Polymers that dont melt when heated, only char. cannot be reshaped and must be moulded when first made.
what is addition polymerisation?
Polymerisation where a double bond is broken and additional monomers can be joined together using the electrons freed from the double bond.
What are the two types of polymers?
natural and synthetic
How is ethene polymerised?
Subjected to high pressure until its liquid, then heated with a catalyst ( bit of O2) until addition reaction occurs.Polyethene is created
How do we name polymers?
POLY- monomer
How does the extent of branching change the properties of a polymer?
Branches keep the chains apart. so the attraction between them is weaker- producing low density substance.Not much branching allows carbon chains to come close, forming HDPE
Where does ethene come from usually?
Cracking of natural gas or naptha
How do side branches affect polymers?
If side branches are on one side, its ISOTACTIC and the polymer chains can get close and so its dense.If side branches are wherever they want to be the polymer is ATACTIC and molecules cant get close making a low density substance.
How does cross linking affect polymers?
If theres a small amount of cross linking, asn elastomer is produced, like vulcanised rubber.When heaps of cross linking is introduced, the polymer is thermosetting and the polymer is strongly bonded in all 3 dimensions.
What is cross linking?
Bonding between chains of polymers
How do we make a themosetting polymer?
Heat or chemicals join long linear chains at their lateral functional group.
What does degree of crystallinity affect?
The more crystalline (arranged regularly) the chains are. the harder it is as the chains can get close. If its got low crystallinity its called amorphous and it is lower in density.
How do we increase the amount of crystallinity in a polymer?
Chain length, breanching etc.The less branches the more crystalline
How does the length of a polymer chain affect it?
The longer the chain, the melting strength and b point increase.Also the chains are more likely to get tangled so its less likely to slide over one another like in smaller chains
What is a plasticiser?
Very small molecule that cause the polymer chains to move slightly further apart . Results in softer and more flexible polymer. eg phthalates.
What is an example of an additive to polymers?
Dyes- add colour and provide pattern
What is vulcanisation?
Process that involves heating natural rubber with varying amounts of sulfur to introduce a bit of cross linkingMakes rubber a bit more elastic and durable
What is the monomer of rubber?
Isoprene.
What is a polymer?
A chain of monomers that are linked together through polymerisation
What is a thermoplastic?
Materials that can be softened and remoulded when heated.
What is a thermosetting material?
Materials that char instead of melting when heated.
What affects the properties of polymer chains?
Their different structures
What are plasticisers?
They are added to polymers which make the the chains softer and more flexible.
How does crystallinity affect polymers?
They are regularly organised into lines. The more crystalline a structure is, the greater it’s hardness, tensile strength and opacity.
What affects crystallinity?
The chain length, branching and interchain bonding
