Unit 3: Section 7 - Polymers MDY * Flashcards
condensation polymers disposing of polymers
what does condensation polymerisation involve?
2 different types of monomer, each with at least 2 functional groups
the functional groups react together
a molecule of water is lost for each link form
how are polyamides formed?
the carboxyl groups of dicarboxylic acids react with the amino groups of diamines
to form amide links
how are polyesters formed?
the carboxyl groups of dicarboxylic acids react with the hydroxyl groups of diols to form ester links
what is hydrolysis?
the reverse of condensation polymerisation
water molecules are added back in to break the links
are condensation or addition polymers stronger?
condensation are generally stronger and more rigid
because they are made up of chains containing polar bonds
what bonds are there between condensation polymers?
van der waals
permanent dipole-dipole
hydrogen bonds
what are polyalkenes?
addition polymers
they are made up of non-polar carbon chains
so they are unreactive and chemically inert
what are the effects of polyalkenes being unreactive?
useful - they can be used without reacting, durable
bad - they are non-biodegradable
why are condensation polymers biodegradeable?
they have polar bonds in their chains, making them open to attack by nucleophiles
so can be broken down by hydrolysis
so biodegrade slowly
how can plastics be disposed of?
burying
burning
sorting for reusing or recycling
how can plastics be disposed of by burying?
landfill
when is landfill used?
when plastic is:
difficult to separate from other waste
not in sufficient quantities to make separation financially worthwhile
too difficult to recycle
advantages of landfill?
cheap
easy
disadvantages of landfill?
requires areas of land
waste releases methane (greenhouse gas) as it decomposes
leaks can contaminate water supplies
what happens when waste is burned?
heat used to generate electricity
why does burning waste plastic have to be carefully controlled?
to reduce the release of toxic gases
e.g. polymers containing chlorine produce HCl
how is burning waste plastic controlled?
waste gases from combustion are passed through scrubbers which can neutralise by allowing them to react with a base
but gases still contribute to greenhouse effect
why are waste plastics recycled?
because many plastics are made from non-renewable oil-fractions
how can plastics be recycled after being sorted?
some plastics can be melted and remoulded
some plastics can be cracked into monomers, and these can be used to make plastics or other chemicals
what are the advantages of recycling waste plastics?
reduces amount of waste going into landfill
saves raw materials
cost of recycling is lower than making from scratch
produces less CO2 emissions than burning
what are the disadvantages of recycling waste plastics?
technically difficult
collecting,sorting and processing more expensive than burning/landfill
often can’t remake plastic you started with
plastic can become contaminated
what are polymers?
long chain molecules made from lots of small molecules joined together
what are monomers?
small molecules that join together to make polymers
what is addition polymerisation?
the formation of long chain molecules from lots of small molecules joining together with no other products
formed by double bond of alkenes opening up to form bonds
why are addition polymers unreactive?
all the molecules are saturated
