SECTION
2
You should spend about 20 minutes on
Questions 14-26,which are based on Reading Passage 2
below.
THE DEVELOPMENT OF PLASTICS
|
A
|
When rubber
was first commercially produced in Europe during the nineteenth century, it
rapidly became a very important commodity, particularly in the fields of
transportation and electricity. However, during the twentieth century a
number of new synthetic materials, called plastics, superseded natural
rubber in all but a few applications.
|
B
|
Rubber is a
polymer - a compound containing
large molecules that are formed by the bonding of many smaller, simpler
units, repeated over and over again. The same bonding principle – polymerisation
-underlies
the creation of a huge range of plastics by the chemical industry.
|
C
|
The first
plastic was developed as a result of a competition in the USA. In the
1860s, $10,000 was offered to anybody who could replace ivory - supplies of
which were declining - with something equally good as a material for making
billiard balls. The prize was won by John Wesley Hyatt with a material
called celluloid. Celluloid was made by dissolving cellulose, a
carbohydrate derived from plants, in a solution of camphor dissolved in
ethanol. This new material rapidly found uses in the manufacture of
products such as knife handles, detachable collars and cuffs, spectacle
frames and photographic film. Without celluloid, the film industry could
never have got off the ground at the end of the 19th century.
|
D
|
Celluloid can
be repeatedly softened and reshaped by heat, and is known as a thermoplastic.
In 1907 Leo Baekeland, a Belgian chemist working in the USA, invented a
different kind of plastic by causing phenol and formaldehyde to react together.
Baekeland called the material Bakelite, and it was the first of the
thermosets' plastics that can be cast and moulded while hot, but cannot be
softened by heat and reshaped once they have set. Bakelite was a good
insulator, and was resistant to water, acids and moderate heat. With these
properties it was soon being used in the manufacture of switches, household
items, such as knife handles, and electrical components for cars.
|
E
|
Soon chemists
began looking for other small molecules that could be strung together to
make polymers. In the 1930s, British chemists discovered that the gas
ethylene would polymerise under heat and pressure to form a thermoplastic
they called polythene. Polypropylene followed in the 1950s. Both were used
to make bottles, pipes and plastic bags. A small change in the starting
material -replacing a hydrogen atom in ethylene
with a chlorine atom - produced PVC (polyvinyl chloride),
a
hard, fireproof plastic suitable for drains and gutters. And by adding
certain chemicals, a soft form of PVC could be produced, suitable as a
substitute for rubber in items such as waterproof clothing. A closely
related plastic was Teflon, or PTFE (polytetrafluoroethylene). This had a
very low coefficient of friction, making it ideal for bearings, rollers,
and non-stick frying pans. Polystyrene, developed during the 1930s in
Germany, was a clear, glass-like material, used in food containers,
domestic appliances and toys. Expanded polystyrene - a white, rigid foam -
was widely used in packaging and insulation. Polyurethanes, also developed in
Germany, found uses as adhesives, coatings, and - in the form of rigid
foams - as insulation materials. They are all produced from chemicals
derived from crude oil, which contains exactly the same elements - carbon
and hydrogen - as many plastics.
|
F
|
The first of
the man-made fibres, nylon, was also created in the 1930s. Its inventor was
a chemist called Wallace Carothers, who worked for the Du Pont Company in
the USA. He found that under the right conditions, two chemicals -
hexamethylenediamine and adipic acid would form a polymer that could be pumped
out through holes and then stretched to form long glossy threads that could
be woven like silk. Its first use was to make parachutes for the US armed
forces in World War II. In the post-war years nylon completely replaced
silk in the manufacture of stockings. Subsequently many other synthetic
fibres joined nylon, including
Orion, Acrilan and Terylene. Today most garments are made of a blend of
natural fibres, such as cotton and wool, and man-made fibres that make
fabrics easier to look after.
|
G
|
The great
strength of plastic is its indestructibility. However, this quality is also
something of a drawback: beaches all over the world, even on the remotest
islands, are littered with plastic bottles that nothing can destroy. Nor is
it very easy to recycle plastics, as different
types of plastic are often used in the same items and call for different treatments.
Plastics can be made biodegradable by incorporating into their structure a material
such as starch, which is attacked by bacteria and causes the plastic to
fall apart. Other materials can be incorporated that gradually decay in
sunlight 一 although
bottles made of such materials have to be stored in the dark, to ensure
that they do not disintegrate before they have been used.
|
Questions 14-20
Complete the table below.
Choose NO MORE THAN THREE WORDS from
the passage for each answer. Write your answers in boxes 14-20 on your answer
sheet.
Name of plastic
|
Date of invention
|
Original region
|
Property
|
Common use
|
Celluloid
|
1860S
|
US
|
|
Clothing and
14______
|
15
____________
|
1907
|
US
|
can be cast
and moulded but cannot be softened by heat
|
16 ______
’household items and car parts
|
Polythene
|
1930s
|
17 _________
|
|
bottles
|
Rigid PVC
|
|
|
18
____________
|
drains and
gutters
|
Polystyrene
|
1930s
|
Germany
|
transparent
and resembled to 19 ______
|
Food
container domestic
|
Polyurethanes
|
|
Germany
|
formation
like 20 ______
|
adhesives, coatings
and insulation
|
Questions 21-26
Do the following statements agree with
the information given in Reading Passage 2? In boxes 21-26 on your answer sheet,
write
TRUE
|
if the statement is true
|
FALSE
|
if the
statement is false
|
NOT GIVEN
|
if the
information is not given in the passage
|
21
|
The chemical structure of plastic is very different from that of
rubber.
|
22
|
John Wesley was a famous chemist.
|
23
|
Celluloid
and Bakelite react to heat in the same way.
|
24
|
The mix of different varieties of plastic can make them less
recyclable.
|
25
|
Adding
starch into plastic does not necessarily make plastic more durable.
|
26
|
Some plastic containers have to be preserved in special conditions.
|
|
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