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Natural
rubber, as fabricated in rubber products, combines high strength
(tensile and tear) with outstanding resistance to fatigue.
It has excellent green strength and tack (the ability to stick
to itself and to other materials) which makes it simple to
fabricate. The main weakness is its moderate resistance to
environmental damage by heat, light and ozone, although this
can be an advantage in disposable products like toy balloons
and is not a problem in bulky products like bridge bearings
where practical experience, that is length of time in service,
has shown that degradation is a purely surface phenomenon
and is not greater than, and is often less than, the surface
damage to the concrete and metal parts of the structure.
The technical strengths of natural rubber as a tyre material.
These have been succinctly summarized by Baker as follows:
- high green strength, tack and cohesive properties: these
are essential for maintaining green tyre uniformity and
stability during building and shaping operations;
- excellent adhesion to brass-plated steel cord;
- low hysteresis which imparts low heat generation, which
in turn maintains new tyre service integrity and extends
retreadability;
- low rolling resistance with enhanced fuel economy;
- excellent snow and ice traction for winter tyres and
all-season treads; and
- high resistance to cutting, chipping and tearing.
Natural rubber forms an excellent barrier to water (some
synthetics absorb water and the properties are damaged in
submerged applications, such as off-shore structures, and
is possibly the best barrier against pathogens such as the
AIDS virus (HIV). This is why latex is used in surgical
and medical examination gloves and in condoms.
Natural rubber is an excellent spring material.
It is virtually the sole raw material, other than rayon,
which is used by the automotive industry which comes from
a sustainable source. Nevertheless, its association with
road transport and the problem of global warming may affect
its future prospects both negatively and positively.
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