Lifespan of Zylon (PBO)

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Since I recently acquired a ZLC blade (JOOLA Nobilis) I’ve been wondering about the lifespan of Zylon. I remember some drama about Zylon bulletproof vests breaking down early. I’m wondering if there are any degradation issues when Zylon is used in a table tennis blade.

I’m assuming that it’s probably not a concern because it is protected by the surrounding wood plies from light, moisture, and chafing. But I’m not really sure I understand the “chafing” issue. What do you guys think?

Here is a quote from Wikipedia about Zylon being used in sailboat rigging:

“On modern racing yachts, Zylon is used for parts of the standing rigging. It is used as shrouds and stays. The PBO (polybenzoxazole) fiber is degraded by UV and visible light, seawater and chafing(the problem that caused Zylon to be removed from usage in protective vests for police usage, as shown above), and is therefore protected by a synthetic melted-on jacket.”

(I’m also going to assume that the moisture from water based glue is not going to penetrate through the top ply and onto the ZLC ply ???)
 
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Even Yamaha loudspeaker using Zylon for the driver comes coated with something called Monel alloy to protect it from the ultraviolet ray.

That's why I've always stayed away from Zylon. Other than Carbon fiber, Vectran is the only other fiber that has stood the test of time.
 
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Zylon degrades at elevated heat and moisture, even more under ultraviolet and visible light.

It's been known for close to 2 decades.

Unlike the aramids and polyamides, the PBO Zylon fiber does not recover the strength it loses as a result of the exposure to water vapor. This causes a chemical reaction inside the Zylon fiber which is essentially cancerous.

Exposure to water vapor at lower temperatures can still cause permanent degradation in the Zylon, whereas it has far less permanent effect on the aramids.

Note that Toyobo specifically warns against any exposure to humidity regardless of temperature, and also warns against any exposure to visible light.

Bear in mind that Zylon was invented by DuPont, it is twice as strong in tensile as p-aramid Kevlar when brand new. If there were realistic engineering uses for it, DuPont could have made a genuine killing with it.
Instead, they dumped it when they realized it was a white elephant.
 
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Just wondering why would you worry about the lifespan of zylon ending before the wood plies? If anything wood is more prone to moisture.

I think I’m more concerned about the “chafing”. In some case those vests had a lifespan of 30 months. I could switch from water based glue to rubber cement if I’m concerned about moisture.
 
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Zylon degrades at elevated heat and moisture, even more under ultraviolet and visible light.

It's been known for close to 2 decades.

So. Zylon can become cancerous if it’s exposed to water vapor??? Is a humid day in the summer considered “water vapor”? What about sweat from my hand getting on the side of the handle/blade?


Yeesh. There is a chipped/damaged chunk missing from the edge of my blade where the ZLC is visible. I guess I need to be extra careful now.
 
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Take for example Houston where the relative humidity could reach over 90%, you could literally feel the water vapor in the air. If you wear glasses, you could even see the water vapor forms into droplets if you step outside after cooling down in an air-conditioned place. On days close to 100%, your shirt becomes damp without you sweating.

Sweat is essentially slightly acidic water, even worse than water vapor, as the acidity acts as a catalyst for hydrolysis.
 
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It appears moisture has a residual effect that's much harder to avoid than heat. Now the question is whether the epoxy can keep that moisture out.

https://core.ac.uk/download/pdf/4271410.pdf
It was also shown from the experimental results of the humidity moisture absorption tests that when subjected to a moist environment the fibers will absorb and retain moisture. This effect is also increased when the fibers are subjected to elevated temperatures, however the effects of elevated temperature are essentially the same between 40 and 80°C. The fibers can absorb greater than seventy percent of their own weight in water and even after drying may retain up to five percent of their weight in water. This residual moisture present in the fiber leads to permanent swelling of the fiber and increased space between the microfibrils. This will increase the mobility of the acid molecules present in the fiber.
 
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So. Zylon can become cancerous if it’s exposed to water vapor??? Is a humid day in the summer considered “water vapor”? What about sweat from my hand getting on the side of the handle/blade?


Yeesh. There is a chipped/damaged chunk missing from the edge of my blade where the ZLC is visible. I guess I need to be extra careful now.

I think you may have misunderstood Zeo's quote. I am not sure.

"Unlike the aramids and polyamides, the PBO Zylon fiber does not recover the strength it loses as a result of the exposure to water vapor. This causes a chemical reaction inside the Zylon fiber which is essentially cancerous."

I could be wrong but I do not think that sentence is saying that the Zylon becomes dangerous to humans ie, causing cancer. I think it is talking about the chemical breakdown of Zylon and how the structure of the molecules breaking down and ceasing to function how they previously had as being cancerous as an analogy, cancerous for the Zylon fiber.

Again, I could be wrong. But I believe that is referring to how Zylon as a material begins to break down. And think about it. If you made a bullet proof vest out of Zylon and it was bullet proof. And 40 months later, that is 3 years and 4 months later, that bullet proof vest was as bullet proof as my cotton shirt, that is a pretty rapid rate of decay and deterioration for that material.

And I also see no reason why Zylon, without any kind of protective coating, bonded between wood plies that are consistently subject to sweat from a human hand would be in anything close to resembling a safe scenario simply because it is bonded between plies of wood that are also absorbing the sweat from your hands and the water from the glue. :)

However, since the Zylon is not being utilized in a TT blade for its ability to resist forces like those on a sail in a sailboat, or bullets like a bulletproof vest; but the Zylon is being used for the, give that allows the ball to sink in a little extra and the rebound that causes the ball to leave the blade faster. I am not sure that as the Zylon fibers deteriorate and lose their strength, that that would necessarily be a bad thing.

That breakdown may give older Zylon blades more of that magical dwell time that Arylate blades start with. I am not sure. It is just a theory. But maybe I should pull out my old TB ZLF and test the theory, tell everyone I am correct and decide to sell the blade for some of the crazy prices you see people list Butterfly Black Tag blades for. :)
 
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Oh, by "cancerous" the original poster didn't mean carcinogenic, as in harmful to the human body, but rather to the Zylon fiber itself. Visible light, UV, heat, and moisture are "cancerous" to Zylon as they lead to chemical reaction.

What is not explicitly stated is whether that reaction caused by the initial exposure would continue even in the absence of those harmful elements. In that thesis, it's suggested the Zylon fiber would retain some of the moisture absorbed even after drying, suggesting the hydrolysis would continue.

There's a bigger problem. The way they assemble the blade at the factory(under visible light) means the Zylon fibers have already started breaking down even long before they come off the assembly lines.

 
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The Zylon fiber degrade by UV and visible light, seawater and shafing and is therefore protected by a synthetic melted-on jacket.

You have nothing to worry about the ZLC net, produced from coated zylon fibers woven with carbon.
Even if Some degradation happen, for some very hypothetical reasons, this degradation would not be sensible, and as zylon is much stronger than arylates and aramids, it will take a lot of time for zylon to become weaker.

A lot of Formula 1 car parts are made of zylon and if they can trust it, why we should not?

At the end I don't find it very appropriate to compare the extremely high forces problems, concerning human life, to the hypothetical problems with what we call "TT bat".
 
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Okay I read the “cancerous” statement wrong. I now understand that it was being used as a metaphor and was not referring to Zylon becoming carcinogenic. Thanks for pointing that out.

Separate question, since there is a chunk of outer ply wood missing from the edge of my blade (with the ZLC visible) should I try to fill it in with something? If so, what should I use?
 
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Okay I read the “cancerous” statement wrong. I now understand that it was being used as a metaphor and was not referring to Zylon becoming carcinogenic. Thanks for pointing that out.

Separate question, since there is a chunk of outer ply wood missing from the edge of my blade (with the ZLC visible) should I try to fill it in with something? If so, what should I use?

Don't worry about this stuff. Just play with and enjoy your racket. You don't hit the ball with that part of the racket. It makes absolutely no difference.
 
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if the zylon has been properly "wetted out" with epoxy pre-assembly of the blade and then i assume the layers were assembled together under pressure the Zylon should be "encased" and most of the above "fears" should be groundless.
I would consider taking a slightly thinned down epoxy and gently rub it on to the edges of the blade to make sure this part is also protected and sealed.

Dribble dribble dribble blah blah ;)
 
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You may keep the light and moisture out, but the heat will still cause it to degrade, albeit at a much slower rate. Long-term storage in the southern hemisphere becomes a problem.
 
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To seal a blade so that NO moisture gets in, you would have to do muliple, thick layers so that there are no places where moisture can sink into the wood. That would drastically impact the playing characteristics of the blade. You would also have to seal the edges multiple times and the handle; and on the handle, you would have to seal even thicker than the rest of the blade. You would also have to reseal every time the blade got a ding.

As far as I am concerned, sealing may give a mild protection from water seepage but if you have sealed to the point where it stops all seepage, then you would seriously impact the playing characteristics of the blade. To my mind, sealing is best used as a very thin layer that will protect the top ply from splintering when changing rubbers. But not to make the blade air tight.

With all wood blades, the playing characteristics, over time, as the wood ages, can improve. The blade will often get more feeling and become crisper as it ages. So, I don't think you would want to completely seal the blade to stop this with any kind of blade.

And if you don't seal the handle, lots of moisture will seep from the handle to most of the rest of the blade. That is what the pours of the wood grain were actually designed to do. When the wood was in a tree, that is how water gets from the roots to the leaves.

And with water based glue, every time you put rubbers on, you are putting water directly on the blade face. So, unless there is enough sealant to change the playing characteristics of the blade, some of that water WILL seep in to the wood.

So, trying to avoid moisture absorption in a blade played in a sport where people sweat and where water is applied to the blade to put the rubbers on....well, I think there are better things to worry about.

I am not even sure how Zylon breaking down and deteriorating would affect playing characteristics. Would it make the blade feel better or worse?

With too much sealant, I could say the same thing. Would it make the blade feel better or worse? NCT is a coating that Stiga puts on some blades to make the top ply harder. It is basically like a layer of sealant that is very hard. Most sealants would be way softer than the NCT coating though. But if I liked the way a blade felt, I would not mess with it by adding sealant to change the feeling. However, I like the way my OSP blades have aged and become crisper. :)
 
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Whether you seal or not it won't change your blade overnight. If that is your daily driver, I doubt one will notice. Just enjoy what you like. If a blade is ZLC but after 5-10 years it deteriorates so much, that you don't like it anymore. It's still great value/time/enjoyment, even if the blade costs 200€. (buying a 200€ blade every 5 years does not sound bad...)
 
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