[Karla]

In the Netherlands we sometimes use reeds on the roof of a house (thatch roof). Normally the reeds are suppressed with long staff of ca 2-3 m length (thicknes 0,5 cm) that are attached each 30 cm with metal threads+screws on the roof through the reed cover. But we have reasons not to use metal threads and are thinking of using Nylon 6 tiewraps (7,5 mm) through screw eyes in de roof.
However we are uncertain if this Nylon 6 tiewraps are sufficient strong to work for the lifetime of the reed roof (thatch) of ca 30 years.
We both have a rather technical background and know nylon 6 is strongly weakened by higher temperatures and humidities (studied many technical tables). But to translate it in practice .
Who can say something wise out of much experience with nylon 6 (tiewraps) attachments under conditions mentioned here under during 30 years? Gut feeling.
We don't like of course after some years the new reed cover is coming of the roof.

- temperature range outside minus 20 C to plus 40 C
- humidity range outside 25% to 90% (later for periods of some weeks max)
- max tensile power 10-15 kg per tiewrap

[wildfyr]

Nylon is vulnerable to long sunlight exposure. Is this part exposed to the Sun?

[Enthalpy]

Do not trust polymers outdoors. Unless you have very special ones.

A bin liner or plastic bag gets destroyed in two years under sunlight. Or a plant pot.

Usual polyamides are destroyed by sunlight's UV.

[hollytara]

If you go to one of the sites that specializes in cable ties and zip ties - they sell UV rated versions for outdoor use.  You can also get other materials that might be more resistant, like Tefzel. 

U-Line and Cable-Ties unlimited are the ones I have used. 

[Karla]

Nylon is vulnerable to long sunlight exposure. Is this part exposed to the Sun?

It will be the type with carbon in that makes more UV-resistant.

[Karla]

If you go to one of the sites that specializes in cable ties and zip ties - they sell UV rated versions for outdoor use.  You can also get other materials that might be more resistant, like Tefzel. 

U-Line and Cable-Ties unlimited are the ones I have used.

Hello, thanks for your reaction.
It hardly gets UV for is under the reeds, but we also thougt about the UV resistant type with carbon 'enriched'.
We have more thinkings about the creep after years and eventually tearing of the tieraps. Experiences?
We will have a look at the Tefzel and the sites you mentioned, thanks.

[Karla]

Do not trust polymers outdoors. Unless you have very special ones.

A bin liner or plastic bag gets destroyed in two years under sunlight. Or a plant pot.

Usual polyamides are destroyed by sunlight's UV.

Do not trust polymers outdoors. Unless you have very special ones.

A bin liner or plastic bag gets destroyed in two years under sunlight. Or a plant pot.

Usual polyamides are destroyed by sunlight's UV.

The tieraps are about under the reeds, but even then we take the carbon enriched UV resistant version.
We are more concerned about the creep after years (to failure?); creep reinforced by T and humidity outdoors.

[Enthalpy]

Polyamide is among the good guys against creep. If used far from its yield strength, it should live long. Carlowitz' Kunststofftabellen (excellent but 89€) tells for unloaded PA6-6: E~2.5GPa, versus ~0.6GPa creep modulus for 1000h, rather good. Creep isn't linear so this modulus doesn't apply to smaller loads and longer duration.
I haven't found the creep behaviour of ETFE (Tefzel) in that booklet but generally, I wouldn't trust a fluoropolymer under lasting loads.

I've never seen an influence of humidity in the creep behaviour. Maybe there is none, or nobody has investigated, or I missed the reports. ETFE is insensitive to humidity, PA is very sensitive to humidity that makes it swell but doesn't influence much its short-time strength.

Carbon black makes miracles to protect tyres against UV, so if your ty-rap are below the thatch, it's worth trying. I hope it's your own house, not at a customer?

You might try to experiment. Load a set of ty-rap at the expected force, put them at different temperatures until they break, measure their duration, deduce the acceleration by the temperature, pretend that this acceleration applies to room temperature, deduce the duration at room temperature. That's how the reliability of electronic components is "tested". It's not really credible because the extrapolation is from one month to tens of years.

Or ask the ty-rap manufacturer rather. They may have knowledge about long-time loads. The answer would resemble: for decades, limit the force to X newton.