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April 05, 2022 10 min read
The Discovery of UHMWPE
A detailed history of the discovery of UHMWPE by DSM is available here:https://www.thedyneemaproject.com/en_GB/the-fabrics/dyneema.html
To summarize it and minimize the human interest angle:
Scientists at DSM in the Netherlands discovered ultra-high molecular weight polyethylene fibers by accident in 1963, during a series of experiments in fractionating out different polyethylene lengths from a solution. (These experiments were probably done with an eye towards the production of packaging materials.) It was quickly discovered that these very long-chained polyethylene fibers were incredibly strong, but, initially, only small amounts were produced, and they seemed to be more of a scientific curiosity than a useful material. For, at the time, those UHMWPE fibers were nearly impossible to orient in solution, so they’d typically form intractable aggregates and clumps. As discussed in Part 1, fiber composites benefit from orientation, and a tangled and knotted clump of fibers has very little actual strength or practical use.
In 1978, 15 years after the original discovery, DSM engineers discovered the now-famous gel-spinning method, which Dr. Piet Lemstra, who worked on the project, described as follows: “It’s actually very simple. The more you dissolve the long chain molecules in a solvent, the more they become separated. Then you cool it down to a gel state and the molecules are more or less disentangled, so it is easy to stretch them. You can then remove the solvent, or later, during the stretching/drawing process – either way you end up with nearly perfectly aligned molecules.”
The development of this gel-spinning process enabled the industrial production of UHMWPE fibers. But DSM was not an industrial fiber company, it was -- and, to a large extent, remains -- a fertilizer and agricultural product company that discovered UHMWPE fibers by accident. The UHMWPE “team” at DSM was a self-described skunkworks crew that did their experiments in their spare time and on weekends, the corporate bean-counters at headquarters had little interest in figuring out how to develop UHMWPE fiber products, and outside consultants who were brought in to evaluate its commercial potential did not think very highly of it. “This [consulting] company said the fiber was just candlewax unable to resist high temperatures and it lacked any good properties. They saw no future in it,” said Lemstra. “And the management at DSM believed them.” Ultimately, UHMWPE development was put on hold at DSM.
But just a couple of years later, in the very early 80s, Allied Signal (now Honeywell) obtained a patent on a strikingly similar UHMWPE fiber product. It seemed identical in all respects save melting point; Allied Signal claimed that the melting point of their material was 20-30 degrees higher than that of DSM’s fiber. As it turned out, the two UHMWPE fiberswere effectively identical, the melting point difference was due to a methodological error on Allied Signal’s part, and, as the DSM patent had priority, Allied was compelled to purchase a license for the original DSM patent. This had major consequences for both companies.
Over at DSM, this licensing arrangement finally got management to believe in the commercial potential of UHMWPE. Though still adamant in the belief that they can’t produce it in-house because they are not a fiber company and have no expertise in the mass production of such materials, they reached out to Toyobo in Japan. Toyobo were, and remain, the world’s largest producer of carbon fibers, and seem to have been very impressed with UHMWPE’s potential. The two companies worked out a production and distribution arrangement, where Toyobo would make fibers under license for DSM, which culminated in the joint commercialization of Dyneema. Initially, the military market was not targeted, and Dyneema was primarily utilized in lightweight ropes, nets, and sports equipment.
Allied, with the license in hand and no potential intellectual property disputes on the horizon, started marketing their own fiber, Spectra-Shield, as a competitor to Dupont’s Kevlar. In the USA, throughout the 1980s and 90s, they did not meet with much success. DuPont countered their efforts with an effective marketing campaign which showed how Spectra-Shield would weaken at moderately high temperatures, starting at roughly 160°F. The US military, characteristically wary of new materials and new armor systems, came down on DuPont’s side and viewed Spectra-Shield with guarded suspicion.
The First UHMWPE Helmet and Early UHMWPE Body Armor Plates
Although they were slow to adopt UHMWPE, the US Military generously funded some research into the material. In 1987, Allied initiated a military-funded research project (DAAK60-87-C-0089/D) for the development of a PASGT-style helmet made out of Spectra-Shield composites. This was perhaps the first project to investigate UHMWPE in rigid armor systems, and much of the project consisted of identifying the optimal resin system for use with UHMWPE fiber laminates. Multiple resin systems were tested over a period of five years, through the development and testing of many prototype batches. A 50:50 mixture of a vinyl ester resin with polyurethane was eventually settled upon -- very similar to the resins which are today used in helmets and hard armor laminates. With the utilization of this resin, the project’s “Spectra 1989” helmet performed roughly as well as the Kevlar PASGT, both in terms of backface deformation and absolute ballistic performance,at a 20% lighter weight! Despite this initial promise, and for reasons that are not entirely clear, it would be nearly 25 years before UHMWPE composite helmets were issued to American troops.
Other military forces, however, were more open-minded. (Or perhaps less beholden to DuPont, which, back then, was completely opposed to the adoption of UHMWPE fiber composites in armor.) Allied exhibited their Spectra-Shield material at the French defense trade-show Milipol in 1991. The timing was right; this was just as low-level conflicts in the Balkans were starting to heat up, and just as European militaries were looking to modernize their infantry forces, which were often still issued WWII-era helmets. Allied were immediately able to get Spectra-Shield in front of SCERCAT, the French Army’s primary research lab, which then commissioned a number of rapid, impromptu studies into the suitability of Spectra-Shield in comparison with other composite, polymer, and metallic materials for soldier protection. SCERCAT determined that Spectra-Shield performs roughly 80% better than the manganese helmet steel that was then in use, and they also noted thatit is superior to Kevlar. This was a monumental first. By 1992, Allied was shipping PASGT-style Spectra helmet prototypes to the French military for serious T&E. By June of the following year, a local manufacturing agreement with the French manufacturer CGF Gallet was worked out, and the PASGT-style Spectra helmet was adopted by the French Army as the “CGF Gallet Spectra Combat Helmet” -- often shortened to “Spectra Helmet.”
(CGF Gallet Spectra Helmet in OD Green.)
The CGF Gallet Spectra Helmet offered extremely good performance when compared to the other helmets of that era. The largest Spectra helmets weigh about 3 pounds and, when they were new, exhibited a V50 against the 17gr. FSP of over 2200 feet per second. A size L PASGT weighs north of 4 pounds and has alower V50, at around 2000 fps. So the aramid PASGT, then in use and considered quite a “modern” helmet at the time, weighed substantially more, and simultaneously offered inferior performance.
We could go a step further and say that the French Spectra Helmet offers extremely good performance compared totoday’s helmets. For if you look at its ballistic resistance, its weight per finished helmet, and take its oversized PASGT-style geometry into account,it is superior to the ACH and roughly on par with 2017’s mooted “ACH Gen II.” It is also roughly on par with some of today’s UHMWPE helmets, such as the Galvion P series.
That’s not bad for a helmet that was almost fully developed in 1989 and was issued on an Army-wide basis in 1993.
The current French Army helmet can trace its lineage back to the Spectra Helmet; it is, for all practical intents and purposes, “Mark 2” of the 1993 model. But the Spectra Helmet never got the attention it deserved, and today it is mostly forgotten. It was too far ahead of its time.
Indeed, the Spectra Helmet was not nearly as influential as it should have been. It did not influence the development of American helmets in the 1990s and 2000s at all. It was evaluated by the Canadian forces, who subsequently developed a new helmet, the CG634. The CG634 copied the Spectra’s cut and design, but, out of an abundance of caution, was constructed out of aramid rather than UHMWPE.
The Spectra Helmet did, however, strongly influence the development of UHMWPE-based armor plates, which were largely a continuation of Allied/Honeywell’s work on rigid UHMWPE fiber composite systems. (If DSM first discovered and pioneered UHMWPE fibers, it must in fairness be noted that Allied/Honeywell pioneered the development of UHMWPE composites and composite armor with their work in the late 1980s.)
Shortly after the class-leading performance of the Spectra Helmet became apparent, rigid panels of similar construction were tested for use (a) behind ceramic tiles in ceramic armor plates, and (b) in thick standalone body armor plates. The former exhibited starkly superior performance in comparison with the fiberglass and aramid backers that were standard at the time, and rapidly -- within just a few years -- replaced both materials in all but the lowest-end ceramic armor systems. The latter were quickly noted for their excellent performance against lead-core ball rounds such as the 7.62x51mm M80, but did not exhibit a performance advantage over ceramic armor systems against threats with steel cores or very high impact velocities. Because steel-cored threats were, and remain, extremely common, these early UHMWPE composite plates were not seriously considered for mass adoption by any military, but have seen service in niche roles. And it should be further noted that the performance of UHMWPE composite armor plates, without a hard strike face, has improved in the nearly 30 years since those plates were originally tested; today, in some cases, a 10x12” UHMWPE composite armor plate that weighs 2.5 pounds can stop the hard-hitting mild steel cored 7.62x54mmR LPS, which is far beyond the capabilities of UHMWPE composite armor plates in the 1990s and 2000s.
Thus US military helmets may not have been directly influenced by the Spectra Helmet, but armor plate developmentwas influenced, and advances in UHMWPE-based armor plates eventually led to the development of the ECH, which, in turn, has had a huge impact on subsequent US Military helmets.
So the evolutionary chart of the modern helmet, from a materials perspective, goes something like this: French Spectra helmet --> UHMWPE body armor plate --> ECH --> IHPS, Ops-Core RF2, etc.
The Development of the ECH
The ECH, which derived from the UHMWPE technologies then in use in body armor, was developed as a partial replacement for the ACH. It’s something of an understatement to say that the ACH had its share of problems in Iraq and Afghanistan. It lurched from scandal to scandal, some (but not all!) of which were described in the 2019 bookShattered Minds: How the Pentagon Fails Our Troops with Faulty Helmets. One of its problems, as perceived by Army officers in Iraq, was its lack of resistance to enemy small arms fire. Most engagements in Iraq took place within 100 yards, and both sides often went for headshots. A light helmet that offered protection from the rifle threats seen in theater -- primarily 7.62x39mm mild steel core -- was demanded by high-ranking US Army and USMC leadership.
At the outset, in 2009, the requirement was for a helmet that would be simultaneously lighter than the ACHand resistant to certain rifle threats. When it quickly became clear that this was not possible, requirements were relaxed to a merely “light” helmet with the ability to defeat 7.62x39mm at more or less muzzle velocity, as well as 7.62x51mm at a standoff of roughly 300 yards. With the advances made throughout the 2000s in UHMWPE-based hard armor plates and soft armor panels, it was clear to all involved that there was only one way to achieve this: With a helmet made primarily of UHMWPE.
(Primarily. Unlike aramid helmets, which are usually made solely of pressed layers of woven aramid in a resin matrix, UHMWPE-based helmets are never madeentirely of UHMWPE composite sheets. There are usually at least a few layers of a stiffer “structural” material like aramid or carbon fiber, to ensure dimensional stability, durability, compression resistance, and reduce backface deformation upon impact.)
Four vendors proposed UHMWPE-based helmets, and ultimately one of them was selected for initial experimentation and testing. By late 2010, the first prototypes were built and tested. First article testing, though, took a lot longer than that, and the helmet didn’t enter “production ready” status until 2013, four years after the initiation of the program.
By this time, opinions in the military’s program management and development community were mixed. The Navy’s assessment is as follows:
To get to the heart of the matter, there were concerns about ballistic performance against rifle threats in general -- for the ECH only protects against a few rifle threats, and then not always under “worst case” test conditions of muzzle velocity and 0° obliquity. There were concerns over BFD, which, against rifle threats that the helmet was rated to stop, generally far exceeded the 25.4mm limits set in the ACH specification. And, lastly, there were concerns about the possibility of Zylon-style UHMWPE degradation. There was also some consternation over the fact that the ECH cost 3x as much as the ACH to produce.
In light of these concerns, the Director, Operational Test & Evaluation Office (DOT&E) recommended that the ECHnot be purchased or fielded. The Army Surgeon General subsequently made the same recommendation. But warfighters in the Army and USMC communities were insistent, and they won out. The ECHwas fielded; small-batch production started in 2014.
The ECH rolled out slowly, but was received very favorably by soldiers and command. In fact, it was so well received that the ACH and the planned ACH Gen II were unexpectedly depreciated, and the military decided to proceed with a wider roll-out of ECH-type helmets! The new general-issue IHPS helmet was modeled after the ECH; like the ECH, it’s made primarily of UHMWPE composites; like the ECH, it offers protection from 7.62x39mm and similar rifle rounds.
The ECH also spurred the development of lightweight UHMWPE helmets for the civilian, police, and special operations communities. Shortly after it was introduced, Ops-Core and other vendors began releasing high-end UHMWPE helmets which were similar to the French Army’s CGF Gallet Spectra Helmet in weight and thickness, if not in shape and cut! Like the Spectra Helmet, they’re roughly 25% lighter than comparable aramid helmets like the ACH, on an areal density basis.
UHMWPE-based helmets are here to stay.