Selection
Polypropylene vs Nylon Mooring Rope
6 min read
These two sit at opposite ends of the low-cost synthetic range. Polypropylene floats and is cheap; nylon is strong and stretchy. Choosing the wrong one is a common and avoidable mistake.
Side by side
| Property | Polypropylene | Nylon (polyamide) |
|---|---|---|
| Density | About 0.91 — floats | About 1.14 — sinks |
| Break load at equal diameter | Lowest of the common synthetics | Considerably higher |
| Elongation at break | Moderate | Highest of the common mooring fibres |
| Wet strength | Effectively unchanged — absorbs almost no water | Reduced when wet |
| Melting point | About 165 °C — lowest | About 220 °C |
| UV resistance | Lower — degrades faster in sunlight | Better, but still needs protection |
| Relative cost | Lowest | Moderate |
Choose polypropylene when
- The rope must float and stay clear of the propeller — messenger lines, workboat lines
- Harbour work, mooring small craft and general utility use
- Cost per metre is the dominating factor and loads are modest
- The rope will be handled frequently by hand and light weight matters
Choose nylon when
- Shock absorption is required — mooring tails, anchor rodes, surge-prone berths
- Higher break load is needed than polypropylene can give at a manageable diameter
- The line will see heat at a winch drum that would soften polypropylene
Two things that catch people out
First, nylon's wet strength loss is real and should be accounted for in selection, not discovered later. A dry-tested figure is not what the line delivers on a wet deck.
Second, polypropylene's low melting point is a genuine operational limit, not a specification footnote. A polypropylene line surging on a warm drum can be damaged very quickly, and the damage looks like glazing rather than obvious abrasion.
Snapback
Nylon's elasticity means it stores a large amount of energy under load. If it parts, that energy is released violently. Snapback zones must be identified and kept clear during mooring operations. This is a stronger consideration for nylon than for any of the low-stretch fibres.
Frequently Asked Questions
- On small craft, workboats and light harbour duty, yes. For commercial vessel mooring at load, its break load and heat limit generally rule it out as a main line.
Need this applied to your vessel?
Send us the ship design MBL, the required diameter, construction and length, the delivery port and the date. We will come back with a line configuration and the documentation it will carry.
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