Polypropylene is the lightest, most widely used, and most economical rope on
the market. Next to polyethylene it is
the weakest of the common synthetic fibers, though it is still much greater
than the natural fibers, such as Manila or Sisal. Other beneficial
characteristics are long life, ease of handling, flexibility in cold
temperatures, excellent resistance to most acids and alkalis, and good impact
loading. Polypropylene has the tendency to degrade quite rapidly when exposed
to sunlight, thought the addition of UV stabilizers can retard this
degradation. Polypropylene’s specific gravity is below one (0.91), allowing it
to float. The low melting point of Polyethylene, around 166 C (330 F) makes it
an unsuitable rope for high temperature applications. The rope should not be
used in applications where the temperature gets above 120 C (250 F).
Polypropylene fibers used in ropes come in two distinct types, monofilament and multi-filament. These names refer to the diameter of the fibers or denier. Mono-filament are those fibers above 50 denier, and multifilament for those below.