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materials, called plastics, superseded natural rubber in all but a few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—polymerization—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 polymerize 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—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. Do the following statements agree
with the information given in Reading Passage 1? In boxes 1-7
on your answer sheet, write TRUE if
the statement agrees; FALSE if the
statement disagrees; NOT GIVEN if there is no
information on this.
填空题
There is a chemical similarity between rubber and plastics.
填空题
There was a financial incentive for the development of celluloid.
填空题
John Wesley Hyatt was a keen billiard player.
填空题
Celluloid remains hard even when it is heated.
填空题
Celluloid was an essential material for the film industry.
填空题
The thermoplastics included a material known as Bakelite.
填空题
Bakelite had more household uses than celluloid.