organics -polymers Flashcards
what are addition polymers and how are they formed
long chain molecules made from joining together many shorter molecules together ti form a long chain molecule with nothing else produced
what are the monomers for addition polymers
-alkenes
-molecules with C=C
examples of addition polymers
-polyethene
-PVC
-polypropene
are addition polymers biodegradable
non-biodegradable - due to absence of polar bonds in the main chain - all bonds are C-C
-so cannot be attacked by nucleophiles
what are condensation polymers and how are they formed
long chain molecules made from joining together many shorter molecules together to form a long chain molecule with some one small molecules also formed - often water
what are the monmers of condensation polymers
-dicarboxylic acids and diols
-dicarboxylic acids with diamines
-amino
examples of condensation polymers
-polyesters eg terylene
-polyamides eg nylon and Kevlar
are condensation polymers biodegradable
-biodegradable - due to the prescence of polar C-N or C-O bonds in the main chain
-so can be attacked by nucleophiles
-weak bonds
how is a polyamide formed
from a dicarboxylic acid reacts with an diamine
-water is released
-form linkage of C=O-N-H
what is another way that polyamides can be formed
from amino acids
-this is because they contain a carboxylic acid group and an amine
-single acid used then a common repeat unit formed
how are polyesters formed
-dicarboxylic acid and diol
-form water
-have an ester linkage
what monomers combine to make nylon 6,6
1,6-diaminohexane and hexane-1,6-dioic acid
what monomers combine to form terylene or PET
ethane-1,2-diol and benzene-1,4-dicarboxylic acid
what monomers combine to form Kevlar
1,4-diaminobenzene and benzene-1,4-dicarboxylic acid
how is Kevlar strong
forms hydrogen bonding bwt N-H and O on the carbonyl
what are the ways in which polyalkenes can be disposed
-incineration
-recycling – reuse,mechanical,feedstock
what is the incineration process of burning polyalkenes
-burn waste at high temp in a furnace
-release large amounts of thermal energy which can be used for heating and generating electricity
-reduces need for new landfill sites
what are the problems with incineration
products include carbon dioxide which is a greenhouse gas so contributes to global warming
-must be removed from product so adds to extra cost
pros and cons of reusing polymers
-reduce waste
-no need to synthesise polymer or manufacture the item and deliver it
-but needs to be cleaned and sorted
-needs co-operation to not throw out things
-lot of sorting done by hand which is expensive
pros and cons of mechanical recycling
-recycled to make new materials
-after sorting and cleaning - they are shredded into flakes then processed into pellets
-melted down and moulded into new things
-but limited markets for recycled objects and for safety reasons cannot contain food
what is feedstock recycling and how does it work
decomposing polymer
-in absence of air at around 500 degrees
-produces fractions similar to naphta which is used as feedstock for the chemical industry
how can polymers containing ester linkages and amides undergo hydrolysis and polyalkenes cant
Simple esters and amides can be hydrolysed by reaction with either aqueous acids or bases into carboxylic acids and alcohols (in the case of esters) or amines (in the case of amides)
Condensation polymers are linked by ester or amide linkages and so can undergo hydrolysis
Under the action of acid catalysts or biological enzymes the amide and ester links in polyamides and polyesters can be hydrolysed into smaller fragments
Polyalkenes are inert and non biodegradable as a result of the C-C bonds between the monomers in addition polymers
pros and cons of landfill
pros
-buried at specific contained site
-biodegradable polymers will slowly degrade
cons
-limited land available
-slow degradation of plastics
-leaching of toxic compounds
-gas emissions released
