Ropes are supplied either with fiber or steel core, the choice being largely dependent on the application.
Fiber cores are mainly made from polypropylene. This material has the advantage that it neither absorbs nor retains moisture, and thus it eliminates conditions creating internal corrosion. Polypropylene core will have small variations in size and weight and are less susceptible to damage, especially under moist conditions. The following precautions must be taken during use. Do not use fiber core ropes where these are exposed to high temperatures, i.e. above 90°C, this will damage the fiber core. The fiber core ropes should not be used when multi-layer winding is required as the fiber cores susceptible to crushing.
The steel core is designated IWRC (Independent Wire Rope Core) and normal constructions is 7×7. Steel core proves advantageous in severe working conditions involving a low factor of safety, small drums and sheaves, high operational speeds and wide fleet angles. Steel core tends to preserve the circular cross-section of the rope when it is crushed by over-winding on drums. It also prevents the strands from bridging, (being forcibly against each other) which can result in fatigue failure of wires.