3.3.4.3 Addition polymers Flashcards
How do alkenes react with other alkenes?
Via addition polymerisation to form polymers
Why are addition polymers unreactive?
Double bond is broken, resulting in an unreactive alkane
What are the uses of addition polymers?
Insulators
Packaging
Containers
What can poly(ethene) exist as?
HDPE
LDPE
What is HDPE?
Less flexible (used in kitchenware)
Only a few branches, so more tightly packed structure
What is LDPE?
More flexible (used in plastic bags)
Formed under high temperatures and pressures, allowing more branches to be formed, so less tightly packed
What is PVC?
A rigid inflexible plastic commonly used for windows, doors and windpipes. (When it does not have the presence of a plasticiser.)
What is a plasticiser?
Made of different phthalates that allow the plastic to become more flexible as it allows polymer chains to slide over each other more easily, so can be used in PVC, so it is able to be used in wiring and clothing.
What is the structure and properties of addition polymers?
Strong covalent bonds between each monomer and weak VdW forces between chains.
M.p./b.p. is high as there are long chains, so strong VdW forces between chains, so more energy needed to overcome forces.
Describe the hardness of HDPE
Few branches, so chains pack closer together, so more surface contacts, so stronger VdW forces so harder polymers
Describe the hardness of LDPE
More branches so chains do not pack as close together, so fewer surface contacts, so weaker VdW forces, so softer polymers.
Why are addition polymers unreactive? (as in why do they take a long time to decompose)
No c=c double bond during polymerisation, so to break down polymer, strong c-c and c-h bond must be broken which is not possible via biological catalysts (enzymes)
