Addition Polymers Flashcards
(21 cards)
What is a polymer?
A polymer is a very large molecule made up of many small repeating units called monomers
What are monomers?
Monomers are small molecules that can join together to form polymers
What type of monomers form addition polymers?
Monomers that contain a carbon - carbon double bond (alkenes)
What is the general process by which addition polymers are formed?
The carbon - carbon double bond in alkenes opens up and bonds with adjacent monomers, forming a long carbon chain
What is the name of the product of the polymerisation of ethene?
Poly (ethene), also known as polyethylene
What is meant by the “backbone” of a polymer?
The continuous chain of carbon atoms formed when monomers join together in polymerisation
What is the repeat unit of a polymer?
The smallest group of atoms that repeats in the polymer chain
What role do plasticisers play in modifying polymers?
Plasticisers are small molecules that insert themselves between polymer chains, reducing intermolecular forces and making the polymer more flexible
Give an example of how plasticisers modify a polymer’s use (PVC)
PVC (polyvinyl chloride) is rigid in its pure form, but becomes flexible when plasticisers are added for the use of aprons
Why are polyalkenes not biodegradeable?
This is because they have strong, non - polar C-C and C-H bonds in a saturated alkane backbone, making them unreactive and reistant to attack by enzymes and biological agents
What kind of bonds make polyalkenes unreactive and non - biodegradable?
C-C and C-H bonds, which are non - polar and strong
How is low - density poly(ethene) (LDPE) made?
What are the structural features of low - density poly(ethene)?
By polymerising ethene at high pressure and temperature via a free - radical mechanism
It has branched chains due to the random nature of free - radical polymerisation
What are the properties of low density poly(ethene)?
What are common uses of low - density poly(ethene)?
Flexible, stretchy, low density and doesn’t pack well due to branching
Plastic bags, sheeting and electrical cable insulation
How is high - density poly(ethene) (HDPE) made?
What structural feature gives high density poly(ethene)?
By polymerising ethene at low temperature and pressure using a Ziegler - Natta catalyst
It has very little chain branching, allowing chains to pack closely together
What are the properties of high density poly(ethene)?
What are common uses of high density poly(ethene)?
High density, higher melting points and more rigid than LDPE
Milk crates, buckets and plastic bottles
What is feedstock recycling?
A process where plastics are heated to breka polymer bonds and convert them back into monomers, which are reused to make new plastics
What is mechanical recycling?
A recycling method where plastics are sorted, washed, ground into pellets, then melted and remoulded into new products
What are two main ways to reduce plastic pollution?
Reusing and recycling plastics
What is a key advantage of feedstock recycling over mechanical recycling?
It can handle mixed or dirty plastics and produces monomers that are chemically identical to the original ones
What is a limitation of mechanical recycling?
It can degrade the properties of plastics over time due to chain breakage during repeated heating
What is a thermoplastic polymer?
A polymer that softens when heated and can be moulded repeatedly
