Chapter 9-Polymers Flashcards
Define a polymer
A polymer is thousands of small units strung together in one large chain
Define monomer
A single piece of a polymer
How are monomers joined together?
Polymerisation
Do polymers need to consist of all the same monomer?
No they can be different or they can be the same
Define Co-polymers
Are formed when two or more different monomers are used
Define thermoplastic polymers
Polymers that can be heated repeatedly and softened
Define thermoset polymers
Do not soften, but char when heated, they do not reshape.
What type of bonds do polymers require?
A double bond
What are the two main ways of producing polymers?
Addition polymerisation
Condensation polymerisation
What are two important polymers that are produced from ethene?
Low density polyethene
High density polyethene
Explain low density polyethene
Polymer chains support a large number of branches
-The only forces are dispersn forces so the brances keep them apart, this attraction becomes weaker as the branches become further apart.
Explain high density pressure polyethene
- Produced using low pressure
- Chains are very short and have very few side branches, which are held together by dispersion forces
What are some propertes of low denisity poly ethene
-Soft and flexible
What are some propertes of high denisity poly ethene
Ridgid and structured
Define Isotactic in regards to polymers
When side branches are arranged on the same side of the linear polymer, polymers are packed close together resulting in a high density substance .
Define atatic in regards to polymers
When branches occur at irregular points on both sides of the linear polymer.
Low density substance is formed.
What does the prescence of cross-linking affect
Elasticity and rigidity of the polymer
What does a small amount of cross linking produce?
An elastomer, realtively elastic
What does a large amount of cross linking produce?
-Produces a ridgid polymer (thermoset)
How does the degree of crystallinity affect the polymer?
More regions of regular arrangement increase strength
How does the length of the polymer affect the polymer?
The longer the chain, the smaller the polymer
How does the addition of plasticisers affect the polymer?
Plasticisers are small molecules in polymers to make them more flexible.
Do thermoplastics have cross-linking
No
Example of thermoplastic
Polystyrene
