UHMWPE, Test Protocols and Temperatures: What You Should Know

It is no big mystery that I am at best a reluctant advocate of UHMWPE in soft armor. While the material itself *does* have incredible properties, these properties come at a steep price if the end user is not aware of the limitations and weaknesses inherent in the material.

These limitations and weaknesses are exacerbated by (in MY OPINION, ahhh, I promised you would see that word hurled around here!) a tendency to “softball” the armor test protocols. Even the current “best practices” protocols (The FBI and DEA tests for soft armor), have this same inherent kid glove treatment when it comes to UHMWPE containing vests.

“How can this be?” you may ask. Well, let’s review:

UHMWPE (“Ultra High Molecular Weight Poly Ethylene”) is an exceedingly strong material made up of long chains of ethylene molecules. The tensile strength is astounding, exceeding para-aramid (Kevlar/Twaron) and steel easily. It is positively buoyant, waterproof and does not degrade with exposure to UV light (three of the Achillies heels of aramids). However, as has been mentioned before, UHMWPE (regardless of brand- both Spectra and Dyneema are at their root the same basic molecule) will denature when exposed to temperatures exceeding ~168 F.

Think of it as exposing hardened steel to it’s normalization (annealing) temperature. The hardness disappears, and it becomes soft again. Unlike steel, it is impossible to change the UHMWPE back to its “super” state. In its denatured state, the material is identical to the stuff used to make milk jugs.

This denaturation temperature is well-known.

In the real world, temperatures often climb to well above this temperature, in both storage and incidental use (especially hotter regions of the world where .Mil users often find themselves). Why then are the test protocols seemingly designed to AVOID this issue?

Take the current NIJ 06 protocol. It incorporates many new rigors that an armor must pass in order to be certified (a GOOD thing, no doubt), including environmental conditioning. However, the temperature does not exceed the KNOWN denaturation/transition temp of the UHMWPE (highest temp in the conditioning phase is 149 F):

Click to access 223054.pdf

Even the FBI protocol, which excels the NIJ 06 standard in many ways, still only exposes the armor to a MAX temp of 140 F:

http://www.bidsync.com/DPXViewer/FBI_TEST_2006.pdf?ac=auction&auc=108034&rndid=338514&docid=748537

Quite frankly, this is a ludicrous state of affairs. Since temperatures can *regularly* reach 200 F in a car trunk or APC on hot days in CONUS or OCONUS, to not expose armor to these realistic circumstances could be perceived as softballing.

Even recent tests done by DSM which supposedly showed that their UHMWPE material did OK in elevated temperatures STILL tiptoed around the transition threshold temp:

http://www.dyneema.com/~/media/Downloads/Research%20papers/PASS%202010%20-%20Meulman%20-%20DSM%20Dyneema%20-%20Ballistic%20performance%20of%20Dyneema%20at%20elevated%20temperatures.ashx

In the paper, “temperatures up to 90 C (194 F)” were used. However, these temps were *only* applied to hard/rigid armor, which does not experience the same sensitivity as soft armor, most likely due to an insulative effect of the material in thicker section. The soft armor samples were still only exposed to 70 C (which is 158 F, 10 degrees BELOW the known transition temp). The test should have applied the same max temp to ALL samples, regardless of whether they were hard or soft.

In conclusion, test protocols should be designed to apply REAL WORLD rigors to life saving equipment. The current protocols SEEM TO incorporate temperature threshold requirements that allow the limitations and weaknesses of a specific material (UHMWPE) to pass. Designing tests with less rigorous standards so as to avoid excluding a material does not live up to the purpose of testing in the first place. Providing the absolute best lifesaving gear, regardless of any other considerations, should always be the goal.

Tutorial: How to ID Soft Body Armor Materials

Well, you asked, I listened. With all the mail volume I get, this single request was the most common. Thanks everyone for their patience, I have been extremely busy of late with travel, testing, evals, and even a tiny little bit of personal life. 🙂

When it became clear that Zylon was a huge liability and safety hazard in soft armor, lots of people wanted to know if their vests contained it. With the more recent realizations that first and second generation aramid laminates such as GoldFlex and GoldShield, and UHMWPE laminates such as Dyneema and Spectra have notable drawbacks and Achilles Heels, identifying these has also become important.

And so, without further ado, here is how you determine what kind of stuff your armor contains.

1. The first step is to field strip your armor. Most concealable vests today are multi-component, consisting of an outer shell or carrier, and an inner ballistic package. These are generally bottom-load, with the closure consisting of strips of hook and loop along the bottom seam. There are some manufacturers that use a top-load, and some that use a “mid-load” with a seam across the middle part of the vest. Regardless, determine how to get your ballistic panels out of the carrier, and we can get to the next part.

2. Look at your ballistic package. About 80-90% of modern vests will have the actual material encapsulated in some sort of secondary shell, usually consisting of GoreTex, or thin Nylon ripstop that has heat sealed edges. If this is the case, skip to part 4, since you will be using texture and feel to determine what you have.

3. If you have one of the 10-20% of vests that does not have the ballistic material encapsulated in a secondary shell, you will be able to use visual means of determining the composition. I have included closeups of the four materials found in vests to aid in identification:

100% Woven Kevlar- The Gold Standard for body armor

A. Woven Kevlar- This is the material you want to see. It appears as a bright yellow fiber, with discernable warp and weft. Ideally, your armor consists of nothing but this.

GoldFlex- Not the most optimal material, but could be worse…

B. Aramid Laminates- This material will have the same bright yellow appearance as woven Kevlar, but will not have any warp/weft. It will appear glossy, shiny, or slippery, due to the plastic film that covers it. Not optimal, but better than the next two.

UHMWPE- Milk Jugs with delusions of grandeur.

C. UHMWPE Laminates- Either Spectra or Dyneema, this material will have a pearlescent, white, shiny/waxy appearance. Less desirable than aramids.

Zylon- “Danger, Will Robinson, danger!”

D. Zylon- DANGEROUS TO WEAR, this material is a liability and should immediately be discarded. Zylon, in its woven iterations, has a bright orange or bronze tint. In its laminate form, it will exhibit the same coloration, minus the weave pattern. Any armor containing Zylon should no longer be worn, and if possible discarded and replaced.

4. If your armor package is wrapped up in a secondary shell material, you have two options: see if there are any rips, tears, or holes in the material of the shell (to allow visual inspection), or rely on tactile sensitivity. The former is only possible if the armor is older, and there is existing wear or damage to the inner shell. Not an ideal circumstance. The latter will not allow you to determine the composition of the armor with very much accuracy, but is better than nothing.

Pull the shell material tight, and feel both the front and the back. If there is a detectable weave texture on both sides, you have a fairly good chance that the vest is made with 100% woven material. If older than 1990, it is MOST LIKELY woven Aramid, though there is a small chance it is Spectra Flex. If newer than 1998, there is a CHANCE it is made with woven Zylon. If you are worried this is the case, making a small slit in the shell material (if the inner shell is heat sealed) or using a seam ripper to pull about an inch and a half of the seam for visual inspection is advised. If handy with a needle and thread, this can be sewn up again.

If the material on one or both sides feels slick/slippery, then it indicates a laminate hybrid or 100% laminates respectively. Again, if it is of grave concern, a small inspection slit may be made in the inner shell. AGAIN, CUTTING A SLIT/RIPPING SEAMS SHOULD NOT BE DONE TO ARMOR THAT IS UNDER WARRANTY, AS THIS MAY VOID YOUR WARRANTY THROUGH THE MANUFACTURER.

Thus concludes the turorial. It will also be helpful to consult the label, and do a little research beforehand to see what materials you vest potentially contains. Hopefully this was helpful in determining your vest’s innards!

And, faithful readers, it is the first of several tutorials I intend to offer. Until next time!