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APPROXIMATE PERIOD: 1939-1979
World War II
During the Second World War Japan invaded South East Asia,
thus cutting off the USA and Britain from their traditional
supplies of natural rubber. Germany and the USSR had anticipated
an interruption to their supplies and had both developed
significant synthetic rubber industries prior to the outbreak
of hostilities. Faced with the loss of supplies from South
East Asia, the British and Americans turned towards (1)
conservation; (2) alternative sources of natural rubber,
and (3) synthetic rubber.
Conservation
Conservation included control of what had become a precious
raw material. Governments eliminated the manufacture of
non-essential items. Recycling scrap rubber via crumbing
and reclaiming became very important. Compounding was adjusted
to minimize the amounts of virgin rubber used.
Alternative sources of natural rubber
Alternative sources were exploited in the Americas and in
Africa. This included wild rubber gathered in the Congo
and Amazon Basins. Rubber bearing plants other than Hevea
were exploited including Funtumia elastica and the Landolphia
vine. In the USSR, Taraxacum Kok-Saghiz, a species of dandelion,
was claimed to be cultivated, but hard facts are difficult
to establish. 3000 tonnes may have been harvested in 1941
from this source which demanded good quality land and high
labour inputs. In California and Mexico there was renewed
interest in guayule and over 10,000 tonnes per annum of
natural rubber from this source were being produced in California
at the peak of production. Other species considered, but
rejected, included goldenrod.
Synthetic rubber industry
During the Second World War the United States was cut off
from its supplies of natural rubber and responded by a huge
investment in synthetic rubber capacity. Fortuitously, the
American Standard Oil Company had entered into an agreement
with the German IG Farbenindustrie for the exchange of knowledge
and had gained access to the process for manufacturing synthetic
rubber. With massive financial assistance from the US Government,
by the end of the War a large synthetic rubber industry
had been established in the USA with an output of nearly
750,000 tonnes in 1945. The rubber (emulsion-polymerized
SBR) was of inferior quality, but improvements in polymerization
(at lower temperatures) and oil-extension improved the properties.
Some commentators consider that this programme was comparable
to the Manhattan Project (which developed the Atomic Bomb).
SBR plants
In addition to the USA there were SBR plants in the former
Soviet Union, Germany and Canada by 1945 and in Italy and
the United Kingdom in 1958 and France, the Netherlands and
Japan in 1960. Although the new SBR was in many ways inferior
to natural rubber, it could be used to displace large quantities
of natural rubber in tyres, especially those only demanding
a low performance. Furthermore, improvements in compounding
led to better properties.
Ziegler-Natta stereospecific polymerization
During 1953/4 two scientists, Karl Ziegler in Switzerland
and Giulio Natta in Italy developed stereo-specific polymerization
which enabled synthetic polyisoprene to be produced in 1954.
The material was chemically virtually identical to natural
rubber. Commercial production began in 1960 and capacity
grew rapidly to reach peaks of 139,000 tonnes in the USA
in 1972; 20,000 tonnes in Latin America in 1976; 150,000
tonnes in Western Europe in 1975 and 86,000 tonnes in Japan
in 1978. A much larger capacity (in excess of 1 million
tonnes) was achieved in the USSR.
New rubbers & thermoplastic rubbers
The same polymerization technique enabled the development
of solution polymerized SBR, polybutadiene and ethylene
propylene rubbers (notably the terpolymer form known as
EPDM). Finally, thermoplastic elastomers were developed
which did not require vulcanization - notably the Kraton
materials, first marketed by Shell in 1965.
Natural rubber research
There was a period of intensive research activity from the
late 1930s until the 1970s performed mainly at what was
successively the British; Natural and Malaysian Rubber Producers'
Research Association (later to become the Tun Abdul Razak
Research Centre). This work established the chemical reactions
which take place during vulcanization and during ageing
(including the effects of ozone); the viscoelastic nature
of raw rubber and how it behaves during mastication and
the establishment of a new discipline: the physics of rubber.
This last studied properties like strength (both tensile
and tear); elasticity and creep and was a major factor in
the acceptance of natural rubber as an engineering material.
Much of this work is encapsulated in two works edited by
Bateman and Roberts. At the same time there was an increasing
understanding both of the rubber tree as such and of its
ability to manufacture rubber in the form of latex: much
of this latter work was conducted in the countries where
natural rubber is produced.
Major threat to natural rubber
Clearly the developments within the synthetic rubber industry
described above presented a considerable threat to the survival
of the natural rubber industry, but its dedication to R&D
activity enabled it to respond by introducing Technically
Classified Rubber in about 1951 and Technically Specified
Rubber in 1965.
Rubber sold by its appearance
Previously natural rubber had been sold on the basis of
physical appearance which in general reflected the cleanliness
of the rubber. Thus there are five grades of ribbed smoked
sheet (RSS): RSS 1 is the most expensive (and best) and
RSS 5 the cheapest (and poorest quality). Unfortunately,
the buyers had no means of assessing the quality of the
rubber which was typically packaged in bare-back bales exposed
to contamination by dirt, rain and seawater during shipment.
Technically Classified Rubber
Technically Classified Rubber (TCR) was introduced in 1949:
it classified rubbers according to their curing characteristics,
and was intended to be international in scope.
Technically Specified Rubbers
Malaysia introduced its Standard Malaysian Rubber in 1965
which enabled purchasers to be aware of the quality of the
rubber which is produced to a technical specification and
is subject to quality control via accurate testing of such
parameters as volatile matter and dirt content. Previously
bales had varied in size: now bale sizes were standardized
and plastic wrapping maintained cleanliness during shipment.
Other natural rubber producing countries produced similar
schemes at about the same time, or shortly afterwards. Associated
with this development, new methods were developed for processing
natural rubber: these involved the comminution of cup lump
and similar materials, or the crumbing of the filed latex,
and the drying of the crumbed material in ovens. The crumbs
are then compacted into bales. One of these processes was
developed by Tan Sri Dr B.C. Sekhar at the Rubber Research
Institute of Malaysia, but the process has since been introduced
widely.
More competitive natural rubber
These developments, and the introduction of containers for
shipment, enabled natural rubber to compete on a more even
basis with the new generation of synthetic rubbers, although
there was an inevitable loss of markets to synthetic rubber
in many less demanding, and in some more demanding applications.
Thus natural rubber virtually ceased to be used in a wide
variety of automotive applications (notably coolant hose
and extruded weatherstripping) where it was displaced by
EPDM.
Modified forms of natural rubber
Beginning in the late 1930s and continuing in the post-War
period, there was considerable effort to develop new forms
(derivatives) of natural rubber. These included rubber hydrochloride,
cyclized rubber, and graft copolymers of natural rubber
with styrene and methyl methacrylate. The last named is
still being marketed. There was renewed interest in modified
rubbers, in the next period, especially in thermoplastic
natural rubber and epoxidized natural rubber.
New natural rubber producers
India and China began large-scale natural rubber production
in the period following 1945. In India most of the production
was established in Kerala and on smallholdings. In China
production was concentrated on Hainan Island and takes place
mainly on collective farms. In India, the late start coupled
with Government involvement, ensured that smallholders achieved
very high levels of productivity (1600 kg/ha per annum,
or triple that in some countries). In China, the cultivators
have to contend with a severe climate: high winds (typhoons)
and low temperatures: nevertheless, productivity is relatively
high. Both have grown to become major producers. Other new
producers have been established in the Côte d'Ivoire,
Gabon and the Cameroon in Africa and Guatemala in Central
America.
Tyres including radial ply tyres
Michelin, in France, had been developing the radial ply
tyre prior to the Second World War, but kept its innovation
secure from the German occupiers and placed the novel tyres
on the market in the immediate Post-War period. Their use
demanded a greater amount of natural rubber, and as radial
ply technology spread through Europe and eventually to the
USA so natural rubber uptake in tyres increased. It should
be noted that the period following 1945 was to see a vast
increase in road construction in Europe and North America
and a vast increase in the number of trucks and cars in
use almost everywhere. Similarly this period saw a great
increase in civil aviation and the size of airliners grew
with the Boeing 747 being introduced towards the end of
this period. More on tyres.
New uses
Several major new uses developed during the Post-War period,
notably the exploitation of natural rubber in civil engineering
applications. Bridge bearings, rail pads and structural
mountings were invented during the 1950s and early 1960s:
this culminated in the development of bearings for the protection
of buildings against earthquakes. The design of dock fenders
was greatly improved. Michelin developed tyres for the Paris
Metro and the system has since spread elsewhere notably
to Canada and Mexico. Such tyres use a high percentage of
natural rubber to meet the severe demands placed upon them.
The hovercraft looked as if it might be a significant new
market, but other developments in transport inhibited progress:
in any event the bulk of the skirts were manufactured from
polychloroprene except for use at low temperatures where
the synthetic became too brittle.
Recapture lost markets
This change was not universal and there is the potential
for blends of natural rubber with speciality synthetics
to recapture some of these lost markets.
Energy Crises
In 1973/4 and 1979 there were the two Energy Crises which
stemmed from the major oil producers limiting their output
and greatly increasing their prices. This radically changed
the competitive position of natural rubber as the price
of synthetics had to rise sharply to reflect the greatly
increased feedstock costs. Furthermore, the natural rubber
industry was better equipped to withstand the financial
slumps which followed the crises. It is possible to discontinue
tapping without a loss of planted area whereas idle synthetic
rubber plant tends to deteriorate. For a short time there
was even an interest in using natural rubber and other plant
materials as "feedstocks" for petrochemicals
Summary
The natural rubber industry was exposed to very severe competition
from a strong and youthful synthetic rubber industry, but the natural
rubber producers responded with a technically-specified form of
rubber which enabled them to compete on level terms. Furthermore,
the Energy Crises radically altered the competitive environment,
at least for a time.
>Part 5
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