Posts Tagged ‘concealable body armor’

With the push to create ever-thinner, ever-lighter concealable body armor, companies cast about for materials that had even better strength-to-weight ratios than UHMWPE. In the late 90’s, they believed they had found a miracle material.

Developed in the late 80’s by SRI International, and marketed by Toyobo a Japanese company, PBO Zylon [poly(p-phenylene-2,6-benzobisoxazole)] promised to be the holy grail of the armor industry. With nearly TWICE the strength and Young’s Modulus of Aramid, and over twice the decomposition temperature (1202 F), Zylon looked to be a champion. Armor companies immediately started producing high-end vests using the new material. Within a short time, laminates began to be used as well, with names such as Z-Shield and Z-Flex.

The armors produced were impressive, unbelievable even. Thinner, lighter, and more comfortable than anything produced up until that time. Nearly a quarter of a million vests were produced before the shine came off the rose.

Despite the impressive statistics put up by Zylon fiber, these were “ideal” numbers. After time in the environment (especially the harsh conditions body armor is subjected to), it was found that Zylon degraded at a horrifying rate. Light and humidity exposure caused as much as a 60% decrease in the effectiveness WITHIN AS LITTLE AS SIX MONTHS. Due to how the fiber was finished (a phosphoric acid scouring process), small amounts of water (such as the vapor found in human sweat) could react with trace quantities of phosphoric acid remaining on the fibers, and trigger those acids to break down the fibers. UV light accelerated the breakdown.

These dangerous properties were brought to light in 2000 by a researcher at a major University, and CONFIRMED by Toyobo in 2001 (who, to their credit, had never recommended this fiber for use in body armor). These findings were dismissed, and Zylon continued to be used in soft armor.

If not for the tireless efforts of individuals such as Kevin “Mad Dog” McClung and Dr. Gary Roberts, this dangerous material may still be used in vests. This in spite of at least 3 deaths directly attributed to Zylon breakdown, leading to vests failing during bullet impacts.

After these high profile failures, and do to the revelations of Zylon’s unsuitability, a rush for the door ensued. Zylon was pulled by numerous manufacturers, and it was decertified by the NIJ for use in armor. The trouble is, a lot of these vests still remain in circulation today, either because the wearer was not made aware of the issue, or unscrupulous sellers feel that making a quick buck selling, essentially, garbage, is more important than the wearer’s safety.

Zylon should never, EVER be used in armor. If you have a vest that contains ANY, it is not safe, even if it is only a small portion. Identification of this material is paramount, and I will be posting a tutorial in a future post to allow people to determine what their armor consists of.

So avoid Zylon, at all costs, and stay safe!

Next time: We look at hard armor. Same time, same channel!

In the late 80’s and early 90’s a relatively new material was making an appearance in concealable body armor. Based on the Ultra High Molecular Weight Polyethylene molecule, this material offered tensile strength 8-15 times that of steel on a weight-to-weight basis. This was up to 40% higher than Aramid fiber. Developed by DSM, this material became known by two different trade names, Dyneema (DSM) and Spectra (Honeywell). Initially, this material was utilized as both a woven panel (which had immediate problems, as will be discussed below), and later in a laminate form (called Shield technology, similar to Gold Shield aramid laminate).

In the same way that aramid laminates utilized a poly-film matrix, so too did Dyneema and Spectra laminates. The UHMWPE fibers in laminate armor materials are unidirectional (all running in the same direction) and offset by 90 degrees in each successive layer. While this material, which is still widely used in soft armor, has impressive performance (much lower AD than aramid based armors, no UV susceptibility, positive buoyancy), there are fatal flaws that an end-user must be made aware of.

In addition to having the drawbacks of aramid laminates (de-lamination/peeling, extremely poor breateability), UHMWPE laminates also suffer from heat sensitivity. The UHMWPE molecule is chemically similar to garden-variety Polyethylene (the same material used in plastic milk jugs). When Spectra or Dyneema is exposed to temperatures above 170 Degrees F, it permanently and irreversibly denatures/reverts to the same milk-jug plastic (which has absolutely NO ballistic properties at all).

Because armor is often exposed to a wide range of temperatures (for example, in many parts of the country, a car trunk/interior can easily reach 180-190 F), this is a major concern. Furthermore, since there is no visible change to the material, there is no way for the end user to know if their armor is still viable, or merely layers of coffee can lid. Originally, woven UHMWPE armors were produced (called Spectraflex), but since the higher surface area of the woven fibers made the armor even more prone to heat degradation (a hot cup of coffee, for instance, would have a greater effect on a woven UHMWPE vest compared to a laminate, due to the vapor/moisture barrier properties of the laminate), they were quickly withdrawn from the market.

In addition, Spectra/Dyneema based armors fare poorly in situations where they may be subjected to contact shots- the hot muzzle blast gasses can melt the armor around the impact area, allowing the bullet to penetrate more layers (sometimes even the entire vest) than would have been possible with a woven aramid based vest. All laminates suffer poor contact shot resistance, but UHMWPE is especially susceptible. I will be dedicating a post on contact shots in the coming months.

What does all this mean for you, the end user? First of all, it is vital to identify armor containing UHMWPE, and to a similar extent, first and second generation laminates (I will be posting a tutorial on armor material identification in the coming months). If you are able to assess your needs prior to purchasing armor, ask yourself if you will be operating in environments that expose the weaknesses of UHMWPE or laminates (potential for elevated temperatures, likelihood of contact shots, requirement for high exertion/perspiration). If none of these circumstances are likely to be encountered, the dangers of UHMWPE/Laminates will be minimized. But if one or more apply, it is strongly recommended you find an armor system consisting of 100% WOVEN ARAMID.

It is important to note that this applies only to soft armor. UHMWPE/Spectra/Dyneema/Aramid Laminates find extensive use in hard/rigid armors (both as a pure defense and as backing material for the strike face. This will be discussed in a later post, but for now, please note that evidence strongly suggests in a rigid configuration, UHMWPE/Laminates do not exhibit the same dangers/weaknesses as when utilized in soft armor.

Next: The most dangerous (to the wearer) soft armor material. Stay tuned.