SSC-Natick Press Release
U.S. Army Soldier Systems Center-Natick
Public Affairs Office
Natick, MA 01760-5012
Contact: Chief, Public Affairs Office
Date: February 15, 2005
Better barriers seal out toxic agents
NATICK, Mass. -- Collective protection shelters with chemical and biological agent protection have existed since the 1960s.
They historically have been heavy, cumbersome, carried a high logistic burden, and above all been very expensive, but research led by the Natick Soldier Center at the U.S. Army Soldier Systems Center here, is on the path to developing a new generation of shelters to solve these challenges.
The U.S military now has only two viable options for chemical and biological (CB) protective materials. These options are either the expensive, high-performance, decontaminable material Tedlar/Kevlar or a lightweight, low-cost liner material, which has minimal physical properties, absorbs agent, is non-decontaminable, and carries the logistical burden of shipping, storage and deployment.
During the past several years, the Joint Science and Technology Panel for Chemical and Biological Defense has funded research to investigate and develop the next generation barrier materials for collective protection shelters.
The goal has been to develop a lightweight material with improved ultraviolet and flame resistance, increased durability, improved permeation properties, and decreased material and manufacturing cost compared to currently fielded materials.
To mitigate risk and provide incremental improvements to existing chemical and biological protective barrier fabrics, near-term, mid-term and long-term solutions have been identified and are currently being investigated.
These solutions are constantly being revised as new technologies emerge and existing technologies overcome technical barriers.
To date, the thrust of the research has been focused on fluoropolymer coatings as an after-market process for general-purpose shelter materials, nanotechnological enhancement of commodity polymers, low-temperature processible fluoropolymers and self-decontaminating barrier materials incorporating catalytically-reactive membranes.
The near-term solution has been focused on improving barrier properties through coating general-purpose fabrics currently used in shelters. This approach has the lowest technical risk and is cost-effective. Its key advantage is providing a dramatic improvement in chemical and biological resistance to standard tent fabric with a minimal increase in weight.
Standard tent fabric is a woven polyester fiber with a polyvinyl chloride (PVC) coating.
This coating serves as both a repellent to liquids as well as a means of heat-sealing the fabric, thus increasing manufacturing efficiency.
A major laminating company, Duracote Corp. in Ravenna, Ohio, was contracted to laminate various low-temperature fluoropolymer films of varying thickness to one side and both sides of the fabric. Initial permeation testing results proved very promising.
The best candidate fabrics from the permeation testing were then subjected to physical testing to ensure the coatings didn't have any negative effects on the composite material, such as flame-resistance, infrared signature or interference with the ability to heat/radio frequency weld the fabric using conventional welding equipment.
Initial test results were very positive, and a limited production quantity of the new CB enhanced polyester/PVC fabric was ordered to build a prototype shelter and conduct operational testing.
Unfortunately, the material hit a technical snag from de-lamination and streaking, but researchers are attempting to overcome this technical barrier to provide a transitional near-term solution.
Approaches just ahead are nanotechnological enhancement of commodity polymers and lower-temperature processible fluoropolymers, which should transition within the next two to four years.
Nanoscale particles introduced into commodity polymers improve barrier properties, and this technology has been applied in various industries, such as food packaging and pharmaceuticals.
Triton Systems, Inc. of Chelmsford, Mass., has successfully demonstrated the improvement in barrier properties for various polymer materials.
Through the introduction of nano-clay platelets at 5-10 percent by weight, barrier properties have increased 30-200 percent for a 10-20 mil thick film.
This increase in barrier properties also is accomplished without significantly changing the physical properties of neat polymers. Furthermore, these platelets have shown an improvement in flame and ultraviolet resistance for the composite.
Triton was contracted by the Army to improve the barrier properties of the currently fielded M-28 liner material as well as improve flame and ultraviolet resistance.
The polyvinylidene chloride (PVDC) barrier is a proven protective barrier. However, improving the flexibility of the barrier film and adding the capability to seal the material with radio frequency equipment could achieve a lower cost of production and manufacturing.
Triton has investigated several proprietary barrier films and demonstrated the improvement of the existing PVDC barrier properties through application of their nanocomposite technology. Initial testing showed a significant improvement in barrier properties through the application of nanocomposite platelets.
Live agent testing was also conducted on Triton's high barrier nanofilm, which showed excellent resistance.
The company is now working on scaling up their technology to produce a non-decontaminable CB-resistant tent liner similar to the M-28. They will also laminate a high-barrier film to a high-strength fabric substrate to produce a decontaminable outer skin fabric. These materials will then be tested and evaluated for physical as well as chemical and biological properties.
Low-temperature processible fluoropolymers also have promise in improving CB protection.
An investigation of commercially-available fluoropolymers and chloropolymers of varying compositions was conducted with the goal of finding a low-temperature processible polymer with improved durability, ease of processing, or improved resistance to chemical and biological agents over the existing Teflon.
Once a candidate barrier material was identified, researchers then needed to find a compatible substrate material. The final composite also needed the physical properties of a general-purpose fabric, which meets military requirements, along with permeation resistance of conventional threat agents for 72 hours with no measured detection.
Federal Fabrics-Fibers Inc. (FFF), of Lowell, Mass., is contracted to produce a void-free lightweight fabric substrate with a chemical and biological barrier, and has successfully demonstrated the ability to produce a low-cost, lightweight, CB resistant, decontaminable fabric.
The company has identified a low-temperature fluoropolymer, which is easily processed with conventional equipment and can readily be heat-welded. The fluoropolymer laminate is also highly resistant to conventional decontamination solutions.
Initial testing of FFF's proprietary low-temperature processible fluoropolymer has shown very promising results, with little permeation in initial simulant testing and little mechanical degradation after decontamination.
FFF has scaled up their facilities and should have production capabilities in place by the end of 2004. Current work is being done to improve efficiency, quality and consistency of the entire process. A prototype shelter will be constructed to further conduct physical, chemical and biological testing on this novel outer skin fabric.
A long-term solution would involve a revolutionary new system such as a self-decontaminating barrier material incorporating catalytically-reactive membranes.
The Army is currently conducting a technology watch to monitor and identify promising new breakthroughs in academia, industry, government agencies and foreign military programs.
Technical barrier gaps, such as the selectivity of the chemical reactions or stability of required enzymes, will have to be bridged in order to become a viable technology for collective protection.
For more information about the Soldier Systems Center, please visit our website at: http://www.natick.army.mil.
***Please note new office symbol for Soldier Systems Center's Public Affairs Office: IMNE-SSC-PA