posted 09-22-2002 16:53               

Roughly twice the tensile strength of p-aramids like Kevlar and Twaron.

This would ideally allow construction of thinner, stronger vests that are amazingly light and flexible.

Brand new level IIIA vests of Zylon based materials are usually capable of defeating threats that would ventilate other vests made of competing materials like P-Aramid or UHMWPE.
Although backface deformation would still be extreme in these situations, the Zylon panels can often remain intact where other vests would have failed.
The Zylon based vests are super light, very comfortable, and very expensive.

Several companies are currently manufacturing vests made of this PBO material, either in whole or in part.
Second Chance, Point Blank, Armor Holdings/ABA/Xtreme Armor are a few of the companies currently advertising the use of Zylon based materials in some of their vests.
Promises of a new age of more wearable vests and increased user safety.

But are they really delivering what they think they are?

Toyobo of Japan has published a PDF document (September, 2001) regarding the strengths and inherent weaknesses of Zylon (PBO fiber).
Apparently, the material is twice as strong in tensile as p-aramids like Kevlar and Twaron when it is new, but manifests some very serious strength degradation issues with visible light, heat and especially humidity.
Read this PDF, and then come back for the rest of this. (You will need Adobe Acrobat 5.0 or later to download it)
http://www.toyobo.co.jp/e/seihin/kc/pbo/technical.pdf

The Adobe PDF file at the Toyobo site shows, among other things:
1) Degradation of as much as 65% strength loss over six months (evidently a day/night inclusive time line) exposure to sunlight,

2) 65+% degradation in 100 hours under exposure to Xenon lights at 83C, and signifigant degradation after minimal exposure to two 35 watt fluorescent lamps.

Interestingly, the degradation curves for 100 hours under Xenon at 83C and "six months sunlight" are nearly identical, as layed out in their graphs. Both show very sharp downward curves upon initial exposure, and then decrease degradation rates as time goes on, but NEVER stop degrading during the term of the experiment.

Bear in mind that the six months of daylight would include 1/2 of that time in near total darkness (night), and about 50% of the remaining time might be strong, direct sunlight. The 50% strength loss occurs in sunlight right at the two month point.(Do the math)

Taken on the average, about 150-300 hours of exposure to strong white light
(6.5-12.5 full 24 hour days) appears to cause an average of 50% degradation in tensile strength in Zylon. Higher temperatures seem to accelerate this degradation.

Also noted by Toyobo is signifigant degradation due to exposure to humidity.

Oddly enough, the material seems nearly impervious to outright immersion in water, but humidity just kills it.
This *may* be due to acids or other chemicals that could be entrapped in the PBO fiber during the fiber manufacturing processes. These acids/chemicals could be activated by the water vapor, and then begin eating away at the material or otherwise altering its structure sufficiently to allow the documented loss of strength.

Given the fact that the armor made from Zylon is tendentially engineered for minimal bulk and maximum wearability under the evidently erroneous assumption that Zylon (as currently packaged) retains all of its "as manufactured" strength after manufacture and wear, the amount of safety margin built in for acrued light, heat and humidity induced strength degradation over time appears to be minimal as well.

Imagine how humid it is between a vest and its sweaty wearer at any given moment.
Then realize that a Goretex cover is specifically designed to allow the transpiration of water vapor.
Guess where the water vapor will migrate to?
Compound that with use/storage in very humid areas, and compound it again by use in elevated temperatures.

Merely sealing it into thermoplastic elastomer (TPE) sheets (Z-Shield type technology) won't help much at all. There is a large body of data showing the strong capillary quality of the fiber.
Exposed fiber ends on the cut TPE laminate material edges will, quite literally, suck water vapor as it becomes available.
[ J. Appl. Polym. Sci. Vol.80, 1030 (2001) An Analysis of Capillary Water Behavior in Poly-p-Phenylenebenzobisoxazole Fibers T. Kitagawa, K. Yabuki ]

Further, the Toyobo PDF document specifically WARNS against any exposure to or storage and use in visible light, and any exposure to "high humidity", even at "room temperatures".

Despite these published warnings from the material's manufacturer, at least one armor maker using Zylon has made no attempts (to date) to keep the Zylon from exposure to bright work lights during both storage and manufacturing procedures.
Serious doubts exist as to whether the other Zylon users and OEM armor material fabricators have made attempts to prevent similar hazardous exposure issues during their manufacturing processes.

Note that there are NO data shown in the Toyobo document to indicate:
1) That there is any recovery of strength after exposure to light/heat/humidity ceases.
Evidently, once some quantity of strength is gone, it is gone for good.

2) None of Toyobo's published data indicates that degradation of strength ceases entirely after exposure to degrading influences ceases.
Is it possible that Zylon gets a sort of ongoing "cancer" from exposure to light and/or water vapor, as opposed to just getting a "sunburn" or fagged out from the humidity? No one has bothered to find out yet.

3) None of Toyobo's published data indicates that drying out the Zylon recovers its strength.
In point of fact, the drying techniques imagined possible for wearers in the field would entail turning the liquid water on the vest into water vapor in order to dry the vest... thereby causing increased exposure to humidity.

4) None of Toyobo's published data shows that a combination of humidity and light exposure would not compound the degradation curves manifested in the other tests. Data does exist to show that greater heat compounds the humidity issue though.
Example: What happens when Zylon is exposed to X amount of light prior to prolonged exposure to extreme humidity under near dark conditions, as inside a vest panel?

We know for a fact that the Zylon materials used by at least one manufacturer are not currently handled and stored in totally dark, zero humidity conditions during fabrication of armor panels, and in laminated variants it is exposed by the laminate material manufacturer to heat sufficient to bond it to the TPE sheets used in the laminate material.
All of these conditions are PROVEN to cause degradation of Zylon...

So, this begs the question:
Just how bad is the degradation by the time the user gets his vest, and how long can he expect it to stop the rated threats?

Zylon may be a marvelous material when used within its very well documented limitations, but it is certainly obvious that NONE of the armor manufacturers or OEM material suppliers have taken all of those limitations into consideration during their design and packaging of the material for use as body armor.
Why?
Good question.

Zylon *promises* to be a really great material, but only if handled and used/packaged correctly.
Unlike UHMWPE based materials, there does appear to be some hope for Zylon, but only if the manufacturers acknowledge the documented engineering limitations of the material, and take steps to protect it from exoposure to degrading environmental influences.

In the meantime, I recommend that users purchase the Second Chance Monarch p-aramid series or other high quality woven p-aramid based vests (no GoldFlex or other aramid/TPE laminates).

posted 09-23-2002 10:48            

Excluding light exposure prior to and during vest manufacture, do you expect that the protection (from light) afforded by the various carriers (concealable, tactical, etc)is sufficient to prevent degradation?

posted 09-23-2002 17:52               

Also, as I stated in the previous post, there is NO published data to suggest that the light induced degradation stops when exposure to light stops. So, even if the carriers are completely photon proof, there may still be risk of ongoing degradation.

posted 09-25-2002 22:24               

In point of fact, Mr. Bachner or anyone else from Second Chance or any other Zylon armor manufacturer that has anything to say about Zylon durability, experiments on Zylon vests after a year or more wear in the field, etc., would be perfectly welcome to make their case heard here.
Especially if they have some hard data to show us.

In the meantime, the Toyobo documents are really all we have to go by, and they do not paint a nice picture of Zylon and its current modes of employment in armor.

posted 09-26-2002 11:49            

I accomplished that task on 24 Sept 02 after reading your 23 Sept 02 posting. In previous commo with SC I attempted to explain to them the concern that these issues raise with the end users of the product, and the negative effect of silence regarding the issue. I believe that you have raised substantive issues, and I have communicated the same to SC. I also believe (and told them as well) that you have sufficient intellectual integrity to be willing to be "proved wrong" provided that you are provided with factual testing data based upon sound methodology. Right or wrong, (I am not questioning your data or preliminary conclusions) this issue needs answers and quickly. Officer/operator safety is paramount, and the reliability of their equipment and the corresponding confidence that comes with that is an important facet of the job. I have worn SC for more than two decades and I believe in the product based upon the character of Richard Davis, and the long term quality record of their products. Because Zylon is now so commonplace in the end user market, the issues you have raised must be dealt with in a factual, decisive and rapid fashion. I am awaiting a response from Mr. Bachner, and I believe that ultimately Richard Davis should personally address this issue. I will follow-up when I receive any further information.

Respectfully

posted 09-26-2002 12:57               

I used to believe in Richard Davis and Second Chance as well. Like I said, I had high hopes for them doing the right thing.
And, if he or Bachner choose to post here, they will be treated with every possible courtesy.
Especially if they bring a pony.

However, since I made Mr. Davis aware of this way back on 9/05/02, he has made no response, comment or otherwise taken steps to address the issues publicly or privately with TF.
Over two weeks to formulate a response, and nothing, not a scrap of response forthcoming yet???
What gives?
What's to hide?
Are they pulling an "Arthur Anderson"?

10,000+ unique hits per day on TF means a LOT of interest in this subject.
Small pond, big ripples.

The long extant Toyobo document has about the same evidenciary impact on armor company credibility as Monica's spoo-stained blue dress did for slick willie.

It appears at present that the brass at SC and the other armor companies know they got caught with their Zylon pants down "en flagrante", and are desperately searching for a way to spin this so that they don't look too awfully negligent in the engineering "due diligence" department.

posted 09-27-2002 15:05               

I have yet to see any follow up to that.

posted 09-27-2002 23:27            

Sir:

You may have inadvertently missed this posting from the "Body Armor Question" thread on the GZ forum. It is the answer as received from Dr. Westrick:

--------------------------------------------
posted 08-20-2002 09:29
Sirs:
I recently received the following information:

"RCD has completed his exploratory testing on the ballistic pads. He oven “cooked” ballistic pads for 24 hours at 220 degrees F the pads are level II’s. Three pads 1. Twaron 2. Kevlar 3. Zylon… we do not make any Spectra soft body armor.

All the ballistic pads performed well vs. 180 grain .44 mag. JHP (~1400 to 1500 fps)… While these tests are not totally scientific, the tests were done in the typical RCD style…just straight forward shoot the pads with strong ballistic threats. NO PENETRATIONS. All the pads performed to expectations with no apparent degradation.

SC is doing further research regarding the materials mentioned.

Aaron J. Westrick, Ph.D."

Respectfully

posted 09-28-2002 18:17               

Like I said before, brand new Zylon should work better than anything else out there.
The RCD oven tests are of interest, but only so far as they serve to demonstrate (dry) heat durability, which was never really in question.
The primary concern, as so eloquently expressed by Toyobo, is over Zylon that has been exposed to heat AND humidity over some extended period of time, and/or humidity and visible light, etc.

posted 07-02-2003 22:22               

IE
Your quote:

quote:

---

1) Degradation of as much as 65% strength loss over six months (evidently a day/night inclusive time line) exposure to sunlight,

---

From the data it shows; “The strength of ZYLON® decreases in the condition of high temperature and high humidity. The residual strength after a 50 hours treatment with saturated steam at 180°C is 40-50%, which is between p-Aramid and copoly-Aramid fiber.”

Now this is at 50 straight hours at 356 degrees in high humidity. Not sure about you guys, but I have never lived in an oven for 2 straight days. If you plan on putting in one, then don’t expect me to come out alive to test the vest!

Your next quote;

quote:

---

2) 65+% degradation in 100 hours under exposure to Xenon lights at 83C, and significant degradation after minimal exposure to two 35 watt fluorescent lamps.

---

The data shows; That the degration is less then or equal to the aramid fibers tested. Why don’t you put all the data out on the table instead of quoting the parts that fit your point of view?

posted 07-03-2003 01:27               

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.

posted 07-03-2003 07:18            

Kevlar also has a serious, irreversible problem with UV exposure. Note, however, body armor is a system and that the degree of Kevlar UV degradation depends upon material thickness because Kevlar is *self-screening*.

posted 07-03-2003 09:05               

That has nothing to do with how much water a vest can wick up and retain in a sponge like analogy.

posted 07-03-2003 09:44               

quote:

---

What the curves do not show is that the aramids will recover a significant amount of strength once they dry out and/or cool down.

---

posted 07-10-2003 14:14               

Evidently Dow Chemical did invent Zylon.
Today, I spoke to a man that was at their initial presentation of it.

Still, they sold it downriver...

Now:

Got any data that refutes the Toyobo tensile life exectancy data they released in early July of 2003? (I think it was released on the seventh, but I'll check for you nitpickers)
It states a 104F, 80 percent relative humidity aging test showed a 18% tensile strength loss in about 300 days, and about 20% at 600 days. That is without light exposure, by the way.

Note that V50 losses can not be expected to be linear with the tensile losses. They are generally much greater. How much greater remains to be fully tested.

The recent shooting in Pennsylvania indicates precipitous losses at about the six month point after exposure to 98% relative humidity and 98 degree F body heat for roughly half of the time (wear/rest cycle). Too bad the only way this data is being actively collected at present is waiting for officers to be shot...

posted 07-10-2003 17:43               

I am concerned enough to tell my fellow officers that they should be aware of this. Personally, I would not wear a vest with zylon materials until this is resolved.

HTH
Clay

Be Safe out there!

Edited to add: This site also has some good info for those following the Zylon story. This page has an updated temp vs humidity curve for Zylon that was updated Jan/03. It shows strength curves at room temp and 104F over 400 days.

This site has some other information that was useful - the news section especially.

posted 07-11-2003 21:01               

PBZ High-Performance Polymers
SRI chemists patented a class of high-performance polymers called PBZs. This technology had been licensed for commercialization to Dow Chemical, which sold its interest in PBZ to Toyobo Company, Ltd., a leading fiber producer in Japan. Toyobo began commercial production under the name Zylon(tm) in 1998. Zylon(tm), also called PBO after its chemical structure, poly(p-phenylene-2,6-benzobisoxazole), is a member of the PBZ class.