Best nylon for fabrics under hot/wet environments 3

[btrueblood]

Doing some research, again, to find a fabric that can withstand 220-230 deg. F, wet (pressurized hot water) environment. The pH condition of the water can be assumed neutral (rare) to fairly strongly alkaline (to pH of 10, but could be limited to less than that if it improves the longevity of the fabric).

This is to form a reinforcement fabric for an EPDM rubber seal. The current winner in these conditions is meta-polyaramid (Nomex), but this material has become difficult to source.

PET fabric has been tried in the past, and come up a failure due to fairly rapid hydrolysis degradation of the fabric. The recent discussion here of PEN and its use for fibers has me thinking about running some trials with that material.

Nylon, or rather polyamides, come up as possibly good for these conditions. Is there a preferred resin that gives the best combination of hydrolysis resistance and can be fiber-spun?

 

[patprimmer]

The best nylon to hydrolysis is nylon 12, followed closely by nylon 11, but they are not so strong at elevated temperatures.

Nylon 6.6 can be stabilised reasonably well to hydrolysis, but will still be plasticised by the water at those temps, as will the 11 and 12, but to only about half the extent.

Data for both hydrolysis and properties after water absorption at those temperatures will be hard to come by. Data at 100 dec C will be available. I may even have it in my library.

Regards
Pat
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[btrueblood]

Thanks Pat. Is it the case that both nylon 12 and 11 can be spun to fibers? I'd assume so, but we both know what assuming can be.

 

[patprimmer]

Yes. They can and are. Nylon 11 is Rilsan.

The number in nylon names equals the number of carbons between functional groups and it's the functional groups that are attractive to water and also degraded by it. Higher number means less influence from water.

Also, as a general rule, the more the functional groups and the more evenly spaced, the more crystalline and therefore the more short term temperature resistance and strength.

Regards
Pat
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[Demon3]

I'd try to use a polymer that doesn't have hydrolysis sensitive bonds so polyamides and especially polyesters of all types are excluded.

What about oriented polypropylene fibers or fabric? That would have great chemical resistance, pH insensitive and more compatible with EPDM so you can get better adhesion.

Chris DeArmitt - PhD FRSC CChem
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[Demon3]

I know these people make high modulus and strength PP fiber and fabric.

http://www.propexbrands.com/

Chris DeArmitt - PhD FRSC CChem
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[btrueblood]

Thanks Chris, agree we would love to find a fabric that would not be susceptible to hydrolysis. I thought PP will go away (get soft and melt) above 220~230 F?

Are poly-aramids not considered polyesters? Maybe they are a unique class. I know Nomex holds up well for us, we are trying to see if there are similar textile polymers we could substitute.

Dunno why they limited my stars. Will try it again...

 

[btrueblood]

Hunh. I was trying to give Pat a couple of stars, but it won't let me, just bounces the star from one post to another. Guess that's the new functionality. Oh well, consider yerself a star, Pat.

 

[Demon3]

I gave Pat a star

For PP fabric check here

http://www.curvonline.com/

The datasheet says the PP material softens at 175C.

Chris DeArmitt - PhD FRSC CChem
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[patprimmer]

I also wondered about the strength of the PP starting to really fall off at those temperatures.

From memory, I thought Aramid was sensitive to hydrolysis but maybe I am thinking para aramid or Kevlar type. The memories are getting dimmer.

I always thought of aramid as a thermoset polyamide in effect.

BT

Have you tried Technora from Teijin or Akzo Nobel or whoever now handles it in the US, that is if the trade embargo implemented by DuPont has lifted. DuPont can hardly continue to claim commercial damage from imports if they cannot supply the market.

My data is nearly 20 years old, so there may be other players. I have vague memories of a second Japanese source and an Italian source, but both where pilot plant status and they may have been para only, not meta.

Regards
Pat
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[clandestinho]

There's a new high modulus PP fiber on the market called Innegra S.

http://www.innegrity.com/index.php

It has a kind of micro porous surface structure that I havent seen before in any fiber. They claim it provides a better grip for rigid composites and perhaps works with EPDM as well.

regards,
Claus

 

[btrueblood]

Pat,

Yes, I've been watching the Teijin stuff rattle out, not sure but I think they are the current supplier for our supplier. I know DuPont now uses the Technora patent to produce aramids, as it is a cheaper/more efficient method (according to wiki and other online sources).

All,

Looking at PP a bit more closely, but everything I see shows the higher-load heat deflection temperature down below our use temperature. Would probably make a lovely reinforcement at more moderate temperatures, though, and as Chris noted, should play nicely with EPDM.

Thanks, we have some new avenues to explore.