How to tell nylon from polyester

[PlankWalker]

I have some 15mm line constructed of braid on braid around 1000 coarser dark grey longitudinal strands.
My gut feeling is its nylon as I haven't come across this construction in polyester before.
Is there any simple test to identify what material this is?

 

[AntarcticPilot]

I have some 15mm line constructed of braid on braid around 1000 coarser dark grey longitudinal strands.
My gut feeling is its nylon as I haven't come across this construction in polyester before.
Is there any simple test to identify what material this is?

Nylon stretches; polyester doesn't. Put it under tension using a winch, and if it can stretch more than (say)`10% of the length tested, it is nylon.

Nylon is quite rare in ropes used on yachts; although strong, it is too stretchy. Could it be climbing rope?

 

[PlankWalker]

It could be climbing rope, I presume they are usually nylon, can you tell the difference by the way the fibres burn or melt?

 

[Adamastor]

Does the core melt under heat?
What does the jacket look like? Any telltale yarn patterns?

 

[Salty John]

Nylon absorbs about twice as much water as polyester. I don't see how this helps much in identifying one or the other, though!

You could weigh it, saturate it and weigh it again. If it gains no more than about 20% in weight it is more likely to be polyester, if around 40% or more, more likely to be nylon. Highly unscientific, I think.

 

[Jaguar 25]

Nylon stretches; polyester doesn't. Put it under tension using a winch, and if it can stretch more than (say)`10% of the length tested, it is nylon.

Nylon is quite rare in ropes used on yachts; although strong, it is too stretchy. Could it be climbing rope?

I use nylon ropes for mooring lines. I would have thought stretch is what you need in a mooring warp to reduce the shock load on the boats cleats, etc.

 

[AntarcticPilot]

I use nylon ropes for mooring lines. I would have thought stretch is what you need in a mooring warp to reduce the shock load on the boats cleats, etc.

As you suggest, nylon is very suitable for absorbing shock loads, hence its use for climbing ropes. However, it can stretch up to 50% of its length, which is excessive for most boating applications

 

[KenMcCulloch]

I have some 15mm line constructed of braid on braid around 1000 coarser dark grey longitudinal strands.
My gut feeling is its nylon as I haven't come across this construction in polyester before.
Is there any simple test to identify what material this is?

From the description it might be some variety of dyneema. The greyish coloured core is typical, the cover may be polyester or something else. If it's 15mm it won't be climbing rope.

 

[lw395]

From the description it might be some variety of dyneema. The greyish coloured core is typical, the cover may be polyester or something else. If it's 15mm it won't be climbing rope.

That was my thought.
Parallel filament with a braided cover.
Probably either something special or just weird.
Are there trace colours in the cover which denote the manufacturer?

 

[William_H]

I think polyester rope will sink in salt water while nylon will foat. Also polyester tends to have a feel a bit like cotton wheras nylon is more glossy and plastic feeling.
These may not be applicable to your rope but that is my general impression. or perhaps I am confusing nyon with polypropelene. good luck olewill

 

[Aeolus]

or perhaps I am confusing nyon with polypropelene.

Yup

 

[Graham_Wright]

It could be climbing rope, I presume they are usually nylon, can you tell the difference by the way the fibres burn or melt?

Ignite that part you think is nylon and snuff out the flame. Guardedly, sniff the smoke. If it attacks your nasal sensors it is probably nylon.
Nylon has a greater than one specific gravity and will sink.

 

[Salty John]

My data on nylon rope shows that it stretches up to 15%, ideal for mooring warps, has an SG of 1.14 and will slowly sink, will absorb water and shrink losing up to 15% of it's strength. It has a high strength to weight ratio and is very durable having a high resistance to abrasion internally and externally.

Polyester stretches less, very abrasion resistant and is, therefore, ideal for the cover on braided line, protecting them from uv degradation and abrasion. SG is 1.38, so it sinks. Flexible and easy to handle, best all rounder.

Polypropylene floats. Other than that it's horrible.

 

[PlankWalker]

I've just done some non scientific stretch tests on the fibres, (I haven't the equipment to stretch 15mm rope at home)
Both the coarse core and finer sheathing fibres broke at about 10 to 15 % elongation so I think it must be nylon.
The smoke sniffing test was inconclusive, my sniffers not being what they used to be.
As I intend to use the line for new mooring lines and a drogue line I think it will be just fine.

Once again thanks for all the advice guys.

Plank

 

[AntarcticPilot]

My data on nylon rope shows that it stretches up to 15%, ideal for mooring warps, has an SG of 1.14 and will slowly sink, will absorb water and shrink losing up to 15% of it's strength. It has a high strength to weight ratio and is very durable having a high resistance to abrasion internally and externally.

Polyester stretches less, very abrasion resistant and is, therefore, ideal for the cover on braided line, protecting them from uv degradation and abrasion. SG is 1.38, so it sinks. Flexible and easy to handle, best all rounder.

Polypropylene floats. Other than that it's horrible.

I'm probably in danger of teaching Granny to suck eggs


Nylon will, in fact, stretch a lot more than 15%. It will stretch 15% and still return to its original length without any change in its strength or other characteristics (elastic limit). However, it can stretch considerably more without breaking, but beyond its elastic limit so it takes a permanent stretch. That's why climbing ropes that have taken a shock load should be discarded - their strength is severely reduced by the non-elastic deformation. The data sheets you're quoting give the elastic limit of the rope, not its ultimate elongation. Other types of rope will break before deforming permanently.

The point is that nylon will absorb shock loads better than other kinds of rope, but short of measuring the length of the rope to check for permanent elongation, there is no way of knowing whether the rope has been weakened by the shock loads. Nylon can be expected to withstand one shock load, but it may not withstand repeated shock loads if they take it beyond its elastic limit. Of course, if the rope is correctly specified for the maximum expected load, this shouldn't be a problem - but a nylon rope that has taken a large shock load should be regarded with suspicion at the very least.

A way of computing required strength for a mooring rope would be to work out the force required to stop the boat from the maximum expected speed within the 15% elastic limit of the rope. So, for a 5 metre mooring line, you need to stop in 0.75 metres (15% of 5). Assuming a maximum speed (v) of 5 metres per second, the deceleration (a) works out at about -17 metres per second squared (0 = v*v + 2*a*distance). For a displacement of 6000 kg, that works out at a force 0f 6000 * 17, = 102 kiloNewtons, or about 11 tonnes (there are 9.8 Newtons in a Kg weight).

Of course, if you are sure the rope will never be required to stop the boat from full speed, you can use a lower velocity. It is unlikely that shock loads from movement of the boat under wind or waves will be anything like so large.

A rope of over 1 inch diameter should be ample for a medium size boat, assuming that the loads I can find for rope are within the elastic limit.

Finally, nylon degrades on exposure to UV light, and may not last as long as polyester rope in permanently exposed positions.

 

[Graham_Wright]

The smoke sniffing test was inconclusive, my sniffers not being what they used to be.
Plank

Good sniffers or not, nylon fumes will send you reeling!

 

[VicS]

Good sniffers or not, nylon fumes will send you reeling!

Combustion of nylon ( like polyurethane) is likely to produce significant quantities of hydrogen cyanide.

Give the fumes a good sniff .

If then still alive probably polyester ( eg Terylene)


If dead almost certainly polyamide ( eg Nylon)


There is a more scientific method.....Lassaigne's test, if anyone wants to look it up but not the sort of thing you'd be able to do at home as a rule

 

[doug748]

I have some 15mm line constructed of braid on braid around 1000 coarser dark grey longitudinal strands.
My gut feeling is its nylon as I haven't come across this construction in polyester before.
Is there any simple test to identify what material this is?

Yes. Nothing difficult or technical.

Attach it to the towing hitch of a car and give about 10 metres a good pull. If it is stretchy stuff you will feel it "give", As AntarticPilot has pointed out, you will also feel it creep back to it's original length.

 

[Nigel_Ward]

This gives the burn test results to identify each.

http://www.tensiontech.com/tools_guides/burning_characteristics.html

 

[claudio]

Basic chemical tests
Polyester is acid resistant, nylon not so much
Polyester is not resistant to alkalis, nylon is

Melting temperature of Polyester is higher than nylon, so if you have a known sample of polyester or nylon, you could try heating them up and compare





Properties
Nylon (Polyamide)
Relative density 1,14
Temperature resistance Can be used below 0°C
Melting point 218°C (Nylon 6)
UV resistance Excellent - fully stabilised
Extension Breaking stretch of 43%
A lot of energy is stored in the rope - mind the security of people
Flexibility Soft and fl exible - becomes harder in use (water uptake ±10%)
Chemical resistance Good resistance to alkalis - limited to acids


Polyester
Relative density 1,38
Temperature resistance Flexible down to –40°C
Melting point 260°C
UV resistance Excellent - fully stabilised
Extension Breaking stretch of ± 24% wet or dry
Flexibility Remains flexible - no water absorption
Chemical resistance Good - except to alkalis

Length measured under reference tension according to EN ISO 9554