Nuremberg, GERMANY, Sept. 25, 2012

Ballistic Resistant Products with Dyneema® Meet High Temperature Requirements, and Pass Real-Time Aging Tests

DSM Dyneema, the producer of UHMwPE fiber and UD, branded Dyneema®, has recently finished two projects to study the long-term ballistic properties of various elements of personal protection equipment, intended for use by law enforcement and military personnel, made with its Dyneema® UD unidirectional composite.

DSM Dyneema is presenting the results of this latest research into ageing in a paper to be given at PASS 2012, the biennial Personal Armour Systems Symposium this year being held in Nuremberg on September 17-21st. Both papers have been peer-reviewed, and accepted by the PASS scientific committee. Data collected confirm the predictions made in accelerated ageing tests that the company presented two years ago at PASS 2010 in Quebec.

The studies were intended to assess the performance of products made with Dyneema®, firstly, when subjected to heat-aging and tested at elevated temperature; and, secondly, subjected to years of real-time use and/or storage.

The studies complement earlier aging tests carried out on Dyneema® UD and Dyneema® yarns materials, and simulated aging tests. The results prove that products with Dyneema® retain specified performance after being subjected to temperatures as high as 85°C - representing conditions at and beyond the extremes of what they are likely to encounter in service. The results also show that Dyneema® UD based products retain performance years after finished products have been made.

1. Effects of high temperature storage

During daily use by a law enforcement officer, body armor stored in a vehicle can be subject to temperatures as high as 67°C, tests by the USA’s National Institute of Justice have shown. In addition, the USA’s Ministry of Defense has defined a climatic category “hot”, applicable for deserts in Northern America, Asia and Africa. In this category, temperatures can reach 71°C.

Based on this information, DSM chose to use 70°C as the temperature for its study for both soft armor and hard armor. In addition, ballistic tests (V₅₀ and P/BFS - Penetration/Back-face Signature) were conducted at higher temperatures, up to 90°C, to show that articles made with Dyneema® UD perform at and beyond requirement even in conditions more extreme than those set in common industry standards.

Soft and hard ballistic packages were conditioned at various temperatures and tested at the conditioning temperatures as well as at ambient temperature. None of the Dyneema® UD grades showed a significant decrease in performance after being conditioned at up to 75°C  for eight weeks (Dyneema® SB), or at up to 90°C for 20 weeks (Dyneema® HB) while tested at room temperature.

When soft armor packages were conditioned and then tested immediately after removal from the conditioning room, a small decrease was observed for 70°C, and this can be solved easily in the design of the article.

When hard armor panels were conditioned and then tested immediately after removal from the conditioning room, no decrease in ballistic performance was observed in V₅₀ tests up to 60°C. Samples tested at 70°C showed a marginal performance change that is easily adjusted in the design of the article.

Above observations on the effect of temperature on the performance were analyzed, using the Cunniff model and tensile tests on Dyneema® fiber at various temperatures. The Cunniff model relates the fiber properties of fiber based armor to the ballistic performance of body armor. It does not take account of matrix, UD construction and/or manufacturing process. Comparison of the results from the V₅₀ tests on elevated temperature samples with predictions from the Cunniff model shows that the effect of temperature in practical tests with soft ballistic packages is comparable to the model, while with hard armor panels the effect is slightly higher than the predictions.

Finally test series have been set-up to show that ballistic articles, made with Dyneema®, can pass tests according to NIJ 0101.04, even after conditioning for 16 hours at 70°C and tested immediately after removal from the conditioning room. These tests have been conducted in accordance with NIJ 0101.04 level 3A, level 3 and level 4.

For NIJ 0101.04 level 3A soft ballistic vests were used, made with Dyneema® SB and a traumaliner. For NIJ level 3 inserts were prepared with only Dyneema® UD as ballistic resistant material. All these articles passed the P/BFS tests after the above conditioning.

In addition to the inserts made of 100% Dyneema® UD, V₅₀ tests were also conducted on inserts with a ceramic strike face. Results showed that the V₅₀ is far above the required Vstop velocity for NIJ 0101.04 level 4 (878 ± 9 m/s), even when testing the inserts at elevated temperature. This result for commercially available inserts shows that a good designed ballistic resistant article can perform at temperatures that are extreme for body armor. This good performance was further illustrated in P/BFS tests in which these inserts were tested in accordance with NIJ 0101.04 level 3 and level 4, immediately after removal from a 70°C conditioning room. No penetrations were observed and all back face signatures were lower than 44 mm.

The conclusion is that the ballistic performance of products made with Dyneema® UD can be designed in such a way, that it complies with the most stringent high-temperature testing standards.

2. Effects of Real-time Aging

DSM Dyneema has also been looking closely at how real-time exposure to mechanical wear and moisture affect the ballistic performance of hard and soft armor based on Dyneema®.

The company has already published studies on the ballistic resistance of artificially aged Dyneema® yarn and Dyneema® UD grades. These showed that yarn and composites retained their tensile properties and ballistic (V₅₀) performance after being conditioned for 8 weeks at 65°C and 80% relativity humidity, equivalent to a real aging time of five years at 35°C - considered a typical baseline requirement for ballistic resistant vests.

Until now, very limited public information has been available on real-time aged ballistic articles. This is why DSM Dyneema chose to evaluate the retention of ballistic performance of used and real-time aged body armor articles made with Dyneema® fiber in a unidirectional composite construction. The articles varied in age from five to over 12 years. Researchers carried out three different evaluations:

• Visual inspection of a set of the articles with evaluation of condition and information on construction.
• Ballistic evaluation of the ballistic performance of Dyneema® UD extracted from samples of aged vests by V₅₀ measurements and comparison with the minimal performance requirements at the time of production of Dyneema® by DSM.
• Ballistic evaluation of the articles according to the standard used for certification at the time of production to verify that the samples still fulfill those requirements.

DSM Dyneema analyzed four different sets of vests, manufactured in different years, from different manufacturers, certified according to different ballistic standards and made with different Dyneema® UD materials.

The main Dyneema® grades available at the time the vests were produced were Dyneema® SB2 and Dyneema® SB21, launched in 1995 and 2001 respectively. Both grades are made of the same basic raw materials: Dyneema® fibers arranged in a similar UD construction, matrix and a thin PE foil. Dyneema® SB21 differs from Dyneema® SB2 in that it has both a lower matrix content and lower areal density.

The aging process of the plies is apparent from a small variation in color appearance of the Dyneema® UD matrix. No delamination or loose fibers were observed in the individual plies for the vest used for the V₅₀ ballistic test. The vest samples selected for the external ballistic test were left intact and therefore the plies were not inspected before the shooting test.

Next to vests, also inserts and helmets were analyzed. A set of four single-curved inserts were manufactured in Germany in late 2005, purchased by DSM in January 2006 and kept in a DSM warehouse for natural aging until they were tested by the TNO testing facility in November 2011. Additionally, a set of two inserts was manufactured in Denmark in 2006 by Roshield (now TenCate). These were made with pressed Dyneema® HB2 material and were tested in 2012 according to NIJ0101.04 level 3.

Finally, a set of eleven inserts (flat and single-curved), manufactured around 2002 -2003 by TenCate Advanced Armor, France, was tested according to NIJ 0101.04 level 3and compared with ten newly manufactured inserts (double-curved)  of similar construction. These inserts were supplied to a non-disclosed NATO army.

Furthermore, three helmets, complete with suspension system and used by a military end-user based in South-Korea, were provided to DSM for this study. Two of the helmets had been manufactured in 2006 and one in 2002.

One part of the vests provided to DSM was subjected to V₅₀ tests in various test facilities. The remainder was used for Penetration/Backface Signature (P/BFS) tests according to the standard certification level at the time of production.

Test results indicate that even for the set of older vests, the V₅₀ values have not changed significantly from the quality control requirements specified at the time of production. Complementary studies undertaken by DSM on a Dyneema® yarn produced in 1997 and on samples for tensile strength measurements every few years until today have also shown tensile strength retention higher than 98%.

The P/BFS tests were performed in the original certification laboratories (among others TNO, and Beschussamt Mellrichstadt) on three of the four sets of vests. All tested vests still fulfilled the ballistic requirements they were certified for, even when they had been manufactured more than a decade ago.

Both sets of inserts of the Series ID 5 and ID 6 were sent to TNO for an independent evaluation of the ballistic performance. For all sets of inserts tested by TNO, namely Series ID 5 and ID 6 and the TenCate insert Series ID 7 and 8, the BFS results met the requirement (<44 mm). No penetration has been observed in any test series.

The helmets were tested by TNO for again an independent evaluation.  They were originally certified to pass a V₅₀requirement value of ≥ 610 m/s against 1.1 gram FSP projectiles at similar conditioning parameters presented in table 5. The results show that all helmet samples retain their ballistic performance as required at the time of certification.

The conclusions of both studies are:

1. Protective articles manufactured with Dyneema® UD can be designed in such a way that these meet the most stringent tests and specifications for temperatures, extreme for body armor.
2. The aging of real ballistic articles did not change the performance of Dyneema® UD over time.

Note: Ballistic resistant articles always need to be handled with care and each article has its own individual use history. Therefore, this study is to be used only as an illustration of the long-term performance tests performed on body armor made with Dyneema® UD in real life and cannot be considered as any kind of guarantee on the part of DSM with respect to body armor made with Dyneema® or any other finished product.

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