Page 16 - Maria Constantino "The Knot Handbook"

A·'
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/1 ,
Polypropylene ropes, how- (-', bulletproof vests. In ropes, howev-
1
/ '
ever, have only one-third of ,'-'· er, tight curves and knots reduce
,'\.
the breaking strength of , \. · strength, so aramid fibres are
\...,.
nylon ropes, and, because ~- used for the core of ropes, which
the melting point is '' are protected by a braided sheath z
-f
quite low (around :: made from another material. ::a
0
150°C/302°F), they HMP, or high modulus c
c
cannot be used for any polyethylene, is the strongest fibre n
-f
task where fri ction could developed so far. Super- light-
0
generate that amount of heat. weight, but with a tensile strength z
Furthermore, polypropylene · '~,.., greater than stainless steel, HMP is
,' , . f "
ropes have low resistance to abrasion . ·''.-_,~,·>-'·2!. used for the core of rope, for fish-
\.l 1 "'f ( •
and must be stored out of direct sunlight, ::: ing lines and in industries where
as they tend to disintegrate when exposed ,Z extra safety margins are required. Because
to UV light. I they are expensive, HMP ropes are not rec-
The more recently developed 'mira- 0111111.ended for practising knot-tying.
cle' fibres are extremely strong and light.
Aramid fibres such as 'Kevlar', developed by Polypropylene ropes are favoured by
sailors, as they are very light and float in
Du Pont in 1965, is twice as strong as nylon,
water. They do, however, have a low
but with a low elasticity. An breaking strength.
extremely versatile fibre,
Kevlar is most fa1nous for
Knots not only have a
being the fibre used to make practical use , but can be
very decorative, too, as
demonstrated by this jury
mast knot.