Rope Fibres
Rope Fibres |
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A very brief, rough survey of the fibres used in marine cordage. The figures in the table below are very rough, and taken from one source without checking; see below for a whine about the lack of objective data here:
| Generic name | Trade names | Floats | Strength of ½" (lb) | Elong. at break | Crit. Temp. | Chafe Res. | UV Res. | Comments |
| polyamide | Nylon | no | 8,500 | 30 - 35% | 300° F | Excellent | Good | Somewhat chafe-prone, stretchy, good against UV; good as a shock absorber (mooring lines etc). |
| polyester | Dacron, Terylene | no | 11,900 | 15 - 20% | 350° F | Excellent | Excellent | Basic low(ish)-stretch fibre; very chafe and UV resistant; basic rigging fibre. |
| para-aramid | Kevlar, Twaron | no | 22,000 | 1.5 - 4.5% | 400° F | Fair | Fair | Strong, very low-stretch, no creep; very fatigue-prone when worked; UV-sensitive. |
| para-aramid | Technora | no | 32,000 | 1.5 - 4.5% | 400° F | Good | Fair | Basically an improved Kevlar. |
| meta-aramid | Nomex | no | Flame-retardant, related to Kevlar; not strong, but useful as a heat-resistant cover. | |||||
| ultra-high molecular weight polyethylene (UHMWPE, HMPE) | Dyneema, Spectra | yes | 25,000 | 2.3 - 3.9% | 150° F | Excellent | Fair/Good | Low MP suggests it should be chafe-sensitive; anecdotal evidence suggests the opposite. Creeps; starts losing strength above 150°F. Newer variants like Dyneema SK75 improve on earlier versions. |
| liquid crystal polymer (aromatic polyester) | Vectran | no | 35,000 | 4 - 5% | 300° F | Excellent | Moderate | Strong, very low-stretch, no creep, somewhat UV-sensitive. |
| PBO (p-phenylene-2, 6-benzobisoxazole) | Zylon | Extremely strong and low-stretch, steel replacement; very UV-sensitive, even in covered rope form. | ||||||
| olefin (polypropylene, polyethylene) | ||||||||
| polypropylene | yes | Floats; cheap; UV/chafe/heat-sensitive | ||||||
| polyethylene naphthalate polyester | PenTec | ? |
It's very hard (OK, impossible) to get real data on chafe- and UV-resistance of the various fibres. It seems to be that it would not be hard at all for someone with the time and a little money to do some objective tests; but as far as I can see, it hasn't been done.
Here's one piece of anecdotal data, though -- apparently bears can chew through Vectran, but not Spectra!
Copyright (C) 1995-2006 Ian Cameron Smith.
visits since 20Sep06.
Last modified: Sun Jan 28 16:07:48 PST 2007 ($Revision: 1.1 $)