Transcript Recent polymer developments

Higher Chemistry
Unit 2(e)
Recent polymer developments
After today’s lesson you should be able to:
 state which type of polymer Kevlar is.
 explain why Kevlar is strong and give some of its
uses.
 state the property of poly(ethenol) and explain how
this property can be altered.
 explain how poly(ethenol) is made.
 state the property of the polymer made from
poly(ethyne) and how this property occurs.
 state the property of poly(vinylcarbazole) and its
use.
 state the property of biopol.
 state the property of the polymer made from low
density polythene.
Kevlar
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Kevlar is an aromatic polyamide.
It is extremely strong due to the way in which the
rigid, linear molecules can pack together.
O
O
C
C
O
O
C
C
N
N
H
H
O
O
C
C
N
N
H
H
O
hydrogen bonds
holding the linear kevlar
chains together
O
C
C
Properties and Uses of Kevlar
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It is heat and fire resistant so is used in the
clothing worn by firefighters.
It is extremely strong so is used in body
armour which offers protection against
handgun fire and knife slashes.
It has a high resistance to abrasion so is
used in brake pads, clutch linings and the
protective suits of motorcyclists.
It is lightweight so is used as reinforcements
in car tyres and to make ropes and cables.
Poly(ethenol)
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It would be assumed that poly(ethenol) would be made from the
monomer ethenol but this does not exist.
Poly(ethenol) is made from the polymer
poly(ethenyl ethanoate) by a process known as ester exchange.
O
O
COCH 3
COCH 3
+
nCH3 OH
methanol
+
nCH3 OCOCH 3
poly(ethenyl ethanoate)
O
H
O
H
poly(ethenol)
methyl ethanoate
Properties of Poly(ethenol)
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Poly(ethenol) is soluble in water.
It’s solubility depends on the percentage of hydroxyl
groups present or the percentage of acid groups
which have been removed. The more hydroxyl
groups present or the less acid groups present the
LESS soluble the polymer.
This is due to the hydrogen bonds forming between
the poly(ethenol) chains rather than between the
poly(ethenol) chains and the water molecules.
Uses of poly(ethenol)
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Used to make hospital laundry bags. When
any infected laundry is placed in a washing
machine the bag dissolves releasing the
laundry. Poly(ethenol) is only soluble in hot
water so that damp laundry will not dissolve
the bag.
Used to make soluble stitches for surgery.
Takes away the need to have stitches
removed after the wound has healed.
Poly(ethyne)
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Poly(ethyne) is made form the monomer ethyne.
It contains alternating single and double carbon to
carbon bonds.
H
C
C
ethyne
H + H
C
C
H + H
C
C
C
C
C
C
H
H
H
H
H
H
poly(ethyne)
C
C
H
Properties and uses of poly(ethyne)
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Poly(ethyne) has delocalised electrons like
benzene.
Because of these free moving electrons
poly(ethyne) can conduct electricty.
If poly(ethyne) is ‘doped’ with iodine it
conducts 100,000,000 times better.
It is used as an ‘antistatic’ material in high
performance loud speakers.
Poly(vinylcarbazole)
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Poly(vinylcarbazole) is made from the
monomer vinylcarbazole.
It exhibits photoconductivity i.e. it conducts
electricity when light is shone on it.
It is used in photocopiers.
Biopol
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Biopol is a natural polyester.
It is a biodegradable polymer.
It was launched in 1990 but production was
ceased in 1999 due to its high production
costs and a shift towards recyclable
polymers.
Photodegradable plastics
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The structure of low density polythene can be
modified to produce a photodegradable plastic.
The photodegradable plastic either has bonds in
its structure that can be weakened and broken
by sunlight, or it contains a chemical additive
which absorbs light and then attacks the polymer
and breaks some of the bonds.
Once a photodegradable plastic is exposed to
light it begins to break down.
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Photodegradable plastics tend to break down
into small particles of plastic rather than
decomposing completely. The idea is that these
small pieces will then biodegrade. Unfortunately,
they are often not biodegradable and so remain
in the environment.
At present, most plastic waste ends up in a
landfill site where it is buried in a dark hole in the
ground. Under these conditions,
photodegradation cannot take place.