Flamability of older nylon Pilot jackets

[arahat]

This question came upon me as I was reading a post in the Fedora lounge about a guy wearing a leather jacket having subjected his jacket to a spot of forced 'fire-testing' by a crazed sales person.

I wonder if anyone knows if the vintage-ish nylon USAF jackets (ie. L-2s & MA-1s etc.)from the late 40s onwards might be of some sort of fire-retardant nylon considering the pilot's inherent environment?

 

[deeb7]

No, nylon can ignite, burn, melt and adhere to the skin ...

That's what led to its ultimate replacement with nomex.

 

[Dr H]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

 

[jacketimp]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

eisnstein...... :ugeek:


we must do lunchtime sometime........ :twisted:

 

[greyhound52]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

Exactly...huh...yeah I agree :lol:

 

[tgd31968]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

How do they deal with the fact that aromatics are less UV stable and prone to breakdown/discoloring over time? Do they add stabilizers or are the effects slow enough to meet a minimum expected life?
Or is the UV stability only an issue for aromatic isocyanates?
You can PM me if we want to avoid turning this thread into a chemistry discussion.

 

[Dr H]

No problem tgd31968, will p.m. you.
Cheers
Ian

 

[Dr H]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

eisnstein...... :ugeek:

Ah, if the cap fits...

...Not! :mrgreen:

 

[rich]

No problem tgd31968, will p.m. you.
Cheers
Ian

Go public! I'd like to learn about this stuff - if I can that is..............
I must admit to wondering about the choice of nylon for flying gear, there must have been reasons - but if you consider what happened to the crew of Apollo 1, maybe the military were similarly oblivious/complacent?

 

[jacketimp]

No problem tgd31968, will p.m. you.
Cheers
Ian

Go public! I'd like to learn about this stuff - if I can that is..............
I must admit to wondering about the choice of nylon for flying gear, there must have been reasons - but if you consider what happened to the crew of Apollo 1, maybe the military were similarly oblivious/complacent?

agreed.........makes interesting reading.....

sure beats what's your latest hh taste like........waht flavours.......

 

[jacketimp]

Arahat
The chemistry/polymer technology has moved on somewhat these days and flame retardant nylon fabrics are available (e.g. ripstop Nylon for parachute material), however this was certainly not the case during the 1940s hence deeb7's comment about the development of Nomex (an aromatic rather than aliphatic polyamide) and related higher performance polymers. Nomex is intrinsically more expensive to produce and much less processible than typical Nylons but (as is the case with most high performance polymers) but it confers significant performance enhancement thus justifying the additional cost. If you want more info. please let me know as I'll be happy to oblige (I research/teach high performance polymers and composites, but won't hijack the thread :ugeek: .

eisnstein...... :ugeek:

Ah, if the cap fits...

...Not! :mrgreen:

a British attitude?

false modesty is as bad as false pride.......

YOU GOT IT YOU FLOUNT IT.........and i'm NOT talking jackets.......

 

[Dr H]

Don't push me now - I'm into assessment mode after Easter so I'll be handing out assignments with personalised feedback, etc. :lol:

I'll try to keep it brief and not too technical with plenty of extra (web-based) reading in journals if you want to go that far... :ugeek:

 

[jacketimp]

Don't push me now - I'm into assessment mode after Easter so I'll be handing out assignments with personalised feedback, etc. :lol:

i'm very very afraid........i'm not your student.............


I'll try to keep it brief and not too technical with plenty of extra (web-based) reading in journals if you want to go that far... :ugeek:

im not an academik......all i want is the destilled stuff......i'm not talking whiskey......

 

[Atticus]

How do they deal with the fact that aromatics are less UV stable and prone to breakdown/discoloring over time? Do they add stabilizers or are the effects slow enough to meet a minimum expected life?
Or is the UV stability only an issue for aromatic isocyanates?

I know nothing about chemistry. Well, maybe a little something about EOH, but other than that, nothing.

But...I have observed that early nomex jackets do fade and change color with time. In fact, they seem to fade to a much greater degree than does nylon. My first edition CWU-45/P is now much lighter and "yellower" than it was when new. I know this because I removed an old patch receiver from its shoulder and found the fabric below to be much darker and "greener" than the rest of the jacket. Also, the fabric under the jacket's collar and pocket flaps is a whole different color than the remainder of the jacket.

I have also observed that, while nomex fabric seems to be durable, nomex thread is not. Many seams in my CWUs have required re-stitching, even the ones in jackets that are only a few years old.

AF

 

[Dr H]

Don't push me now - I'm into assessment mode after Easter so I'll be handing out assignments with personalised feedback, etc. :lol:

i'm very very afraid........i'm not your student.............


I'll try to keep it brief and not too technical with plenty of extra (web-based) reading in journals if you want to go that far... :ugeek:

im not an academik......all i want is the destilled stuff......i'm not talking whiskey......

Don't worry...I can water it down (few ppms here and there)...you may not even notice the difference

 

[tgd31968]

No problem tgd31968, will p.m. you.
Cheers
Ian

Go public! I'd like to learn about this stuff - if I can that is..............
I must admit to wondering about the choice of nylon for flying gear, there must have been reasons - but if you consider what happened to the crew of Apollo 1, maybe the military were similarly oblivious/complacent?

I think nylon was a big leap in terms of weight and performance and cost of processing over leather. I know my m1a is much nicer in cool weather than an A-2, but not as "cool" in my opinion. I think perhaps those factors outweighed the better protection from fires and hot oil that leather might give. Lets face it, cost, performance and safety are all trade offs, even though saftey is always said to be first.

I would guess the temperature in the capsule would have been fatal even if the suits didn't burn. And besides, they probably would have suffocated anyway, and may have. Although if the temp had risen and fallen quickly enough, perhaps they would have had a chance.

Some things I have read indicate that the suits did thier job, but they could not open the hatch quickly enough. If they had a release system, they might have gotten out.

 

[MikeyB-17]

I really liked the fading effect on my 45/P. It had gone from the original OD to an almost pale brown shade-gave a nice character. Must get another.

 

[Dr H]

How do they deal with the fact that aromatics are less UV stable and prone to breakdown/discoloring over time? Do they add stabilizers or are the effects slow enough to meet a minimum expected life?
Or is the UV stability only an issue for aromatic isocyanates?

I know nothing about chemistry. Well, maybe a little something about EOH, but other than that, nothing.

Despite that AF, you have hit on the problem that tgd31968 (sorry, I don't know your name) mentioned concerning light stability. Apologies if readers already know this but the performance fabrics (Nomex and Kevlar - known as 'Aramids') are woven from polymer fibres (remember that polymers are simply long strings of atoms joined together in a repeating pattern, often with many hundreds of thousands of atoms or more in length) just like cotton thread in your 1940s A2 would be sewn with a natural polymer, cotton - a polymer of cellulose (made up glucose (sugar) molecules). But the big difference is that in order to improve the heat resistance (resistance to bullet impact) or tensile strength of the fibres in aramids we need to change our building block (monomer) from glucose to a monomer with rings of carbon atoms in their structure. These have more bonds holding them together and are therefore harder to break apart (molecule from molecule) by heat, force, etc.

But...I have observed that early nomex jackets do fade and change color with time. In fact, they seem to fade to a much greater degree than does nylon. My first edition CWU-45/P is now much lighter and "yellower" than it was when new. I know this because I removed an old patch receiver from its shoulder and found the fabric below to be much darker and "greener" than the rest of the jacket. Also, the fabric under the jacket's collar and pocket flaps is a whole different color than the remainder of the jacket.

But (and it's a big but) the improvement in the thermal and mechanical properties (and flame retardance, etc.) comes with a greater tendency to absorb ultraviolet radiation from sunlight (due to the carbon - phenyl- rings). The UV absorption causes the electrons (arggh...starting to get technical...knew that I couldn't keep it going ) to become more energetic. Some energy can be lost as the electrons drop back down to their lower energy (ground) state but the UV radiation also causes the polymer chains to break down into smaller chains. Some of the broken chains can lose some of the bonds that hold the chains and rings together and as these go the wavelength at which the polymers absorb radiation changes and so the apparent colour changes (it actually shifts from being higher wavelength - more reddish - to lower wavelength - more bluish). This is why your nomex jacket will have faded and yellowed.


I have also observed that, while nomex fabric seems to be durable, nomex thread is not. Many seams in my CWUs have required re-stitching, even the ones in jackets that are only a few years old.

The aramid fibre will have been spun from a wet solution (dry-jet wet spinning that orients the polymer chains and extrudes them from spinneret holes and coagulates them in a poor solvent to make the filaments). This is the yarn that is used in your thread. In the case of the fabric these filaments will have been woven into a conventional cloth. The multiple layers or will offer some protection to the sunlight and additional strength is given by the fibres running in another direction (anisotropic tensile properties) helping to hide some of the weaknesses that will have developed over time. In contrast, the spun fibres are all aligned in one plane (along the length of the fibre yarn) so any weaknesses are magnified and the thread breaks (there's no additional support from threads running at e.g. 90 degrees to the thread).

Okay, school's out now :geek: ...I'll p.m. additional source material to those who want to read more :roll: .

Cheers

Ian

 

[jacketimp]

fascinating ian.......


when you gonna run workshops in the UK?

 

[Dr H]

Ah Neh
Don't tempt me...I can see a practical user's workshop for wearers and collectors beckoning (DNA or spectroscopic analysis of the leather - did anyone say horse sir, goat, steer?- spectroscopic or mechanical analysis of the Nylon/Nomex, XPS for the metalwares)...where does it all end :?:

Couldn't do these things for free though - have to food on the table for the kids :evil:

Incidentally, just involved in some analysis on some paint flakes from the William Kent ceiling at Hampton Court (Cardinal Wolsey's/Henry VIII's/George II's gaff) - trying to use MALDI TOF SIMS (sorry it's all acronyms when you get down to it) to identify whether the binder that William Kent used to prepare the ceiling plaster and apply the pigments was based on egg, fish, or horse - by analysing proteins. Sound familiar - was that HH or steer did somebody say?
:ugeek: :ugeek: