Polymer Fabric Protects Firefighters, Military, and Civilians

Originating Technology/NASA Contribution

PBI fiber
The PBI plant, located in Rock Hill, South Carolina, produced its first commercial bale of PBI fiber on March 18, 1983.

Insulating and protecting astronauts from temperature extremes, from the 3 K (-455 °F) of deep space to the 1,533 K (2,300 °F) of atmospheric reentry, is central to NASA’s human space flight program. While the space shuttle and capsule vehicles necessarily receive a great deal of thermal barrier and insulation protection, at least as much attention is also paid to astronaut clothing and personal gear. NASA has spent a great deal of effort developing and refining fire-resistant materials for use in vehicles, flight suits, and other applications demanding extreme thermal tolerances, and kept a close eye on the cutting edge of high-temperature stable polymers for its entire 50-year history.

In the late 1950s, Dr. Carl Marvel first synthesized Polybenzimidazole (PBI) while studying the creation of high-temperature stable polymers for the U.S. Air Force. In 1961, PBI was further developed by Marvel and Dr. Herward Vogel, correctly anticipating that the polymers would have exceptional thermal and oxidative stability. In 1963, NASA and the Air Force Materials Laboratory sponsored considerable work with PBI for aerospace and defense applications as a non-flammable and thermally stable textile fiber.

On January 27, 1967, the severity and immediacy of the danger of fire faced by astronauts was made terribly clear when a flash fire occurred in command module 012 during a launch pad test of the Apollo/Saturn space vehicle being prepared for the first piloted flight, the AS-204 mission (also known as Apollo 1). Three astronauts, Lieutenant Colonel Virgil I. Grissom, a veteran of Mercury and Gemini missions; Lieutenant Colonel Edward H. White II, the astronaut who had performed the first U.S. extravehicular activity during the Gemini program; and Lieutenant Commander Roger B. Chaffee, an astronaut preparing for his first space flight, died in this tragic accident.

A final report on the tragedy, completed in April 1967, made specific recommendations for major design and engineering modifications, including severely restricting and controlling the amount and location of combustible materials in the command module and the astronaut flight suits. NASA intensified its focus on advanced fire-resistant materials, and given the Agency’s existing familiarity with the fabric and its inventor, one of the first alternatives considered was PBI.

Partnership

NASA contracted with Celanese Corporation, of New York, to develop a line of PBI textiles for use in space suits and vehicles. Celanese engineers developed heat- and flame-resistant PBI fabric based on the fiber for high-temperature applications. The fibers formed from the PBI polymer exhibited a number of highly desirable characteristics, such as inflammability, no melting point, and retention of both strength and flexibility after exposure to flame. The stiff fibers also maintained their integrity when exposed to high heat and were mildew, abrasion, and chemical resistant.

Throughout the 1970s and into the 1980s, PBI was instrumental to space flight, seeing application on Apollo, Skylab, and numerous space shuttle missions. Applications ran the gamut from the intended applications in astronaut flight suits and clothing, to webbing, tethers, and other gear that demanded durability and extreme thermal tolerance.

Product Outcome

Firefighters wearing protective PBI suits during a training fire
Andre Baur, a firefighter instructor in Switzerland, runs out of a training fire that has gotten out of hand. Like many other “Golden Knights” around the world, Andre escaped with only minor injuries.

In 1978, PBI was introduced to fire service in the United States, and Project FIRES (Firefighters Integrated Response Equipment System) lauded a recently developed outer shell material for turnout gear, PBI Gold. In 1983, PBI fibers were made commercially available and a dedicated production plant opened in Rock Hill, South Carolina, to meet demand. In 1986, NASA Spinoff chronicled this first phase of PBI’s history, and Marvel was awarded the “National Medal of Science” by President Ronald Reagan.

Since 1986, PBI has undergone a steady evolution into countless military and civilian applications and established a distinct profile and reputation in the fire retardant materials industry. In 2005, Celanese Corporation sold the PBI fiber and polymer business to PBI Performance Products Inc., of Charlotte, North Carolina, which is under the ownership of the InterTech Group, of North Charleston, South Carolina.

Produced by a dedicated manufacturer that takes great pride in the history and future of the product, the fabrics incorporating PBI have become prominent players in such diverse applications as firefighting and emergency response, motor sports, military, industry, and (still) aerospace. PBI Performance Products now offers two distinct lines: PBI, the original heat and flame resistant fiber; and Celazole, a family of high-temperature PBI polymers available in true polymer form.

  • PBI fabric withstands the dangers associated with firefighting, arc flash, and flash fire. In 1992, lightweight PBI fabrics were adapted for flame-resistant work wear for electric utility and petrochemical applications, and are now providing flame protection for U.S. Army troops in Afghanistan and Iraq. Short-cut PBI fibers were introduced for use in automotive braking systems and PBI staple fibers are employed as fire blocking layers in aircraft seats.
  • PBI Gold blends 40 percent thermal-resistant PBI fibers with 60 percent high-strength aramid, resulting in a fabric which does not shrink, become brittle, or break open under extreme heat and flame exposure. PBI Gold provides firefighters and industrial workers with superior protection and meets or exceeds every National Fire Protection Association (NFPA) and EN 469 (rating standard for protective clothing for firefighters) requirement. In 1994, the New York City Fire Department specified the use of PBI Gold fabric engineered in black for their turnout gear. Over the last 10 years, PBI Gold has grown internationally, with major industrial, military, and municipal fire brigades specifying the product across Europe, the Middle East, Asia, Australia, and the South Pacific.
  • PBI Matrix employs a “power grid,” a durable matrix of high-strength aramid filaments woven into the PBI Gold fabric to enhance and reinforce its resistance to wear and tear while retaining its superior flame and heat protection. In 2003, PBI Matrix was commercialized and introduced in the United States as the next-generation PBI for firefighter turnout gear. In 2008, Matrix will be introduced in Europe.
  • PBI TriGuard fabric is a three-fiber blend of PBI, Lenzing FR, and MicroTwaron designed for flame protection, comfort, and durability. This advanced fabric meets or exceeds all U.S. Department of Labor Occupational Safety and Health Administration (OSHA) and NFPA standards and is certified for wildlands, special operations, and motorsports applications, as well as the petrochemical, gas utility, and electric utility industries. PBI TriGuard and PBI Gold knits are now in use at several major motorsport racetracks around the country.
  • Celazole T-Series is a form-, shape-, and an injection-moldable blend of PBI and PEEK (polyetheretherketone) polymers.
  • Celazole U-Series utilizes PBI’s high-heat dimensional stability, strength, and chemical resistance to allow it to be formed into parts and used in the tools that produce flat panel displays and in the plasma etch chambers used to make semiconductor wafers.

New applications for PBI are continuing to come to light in new fields that demand material stability at high temperatures. PBI is now being developed into high-temperature separation membranes that increase efficiency in ethanol production and separate carbon dioxide from natural gas for carbon dioxide sequestration, and will see application in hydrogen fuel cells. PBI in short-cut form has also been used as a safe and effective replacement for asbestos. Fittingly, PBI may also return to space as part of NASA’s Constellation Program, as the polymer once applied for space suits in the Apollo and Skylab missions is under consideration for use as insulation material in the rocket motors for NASA’s next generation of spacecraft, the Ares I and Ares V rockets.

PBI TriGuard™ is a trademark, and PBI Gold®, PBI Matrix®, and Celazole® are registered trademarks of PBI Performance Products Inc.

Lenzing FR® is a registered trademark of Lenzing Fibers GmbH.

MicroTwaron™ is a trademark of Akzo N.V.

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Polymer Coats Leads on Implantable Medical Device

Originating Technology/NASA Contribution

Langley Research Center’s Soluble Imide (LaRC-SI) was discovered by accident. While researching resins and adhesives for advanced composites for high-speed aircraft, Robert Bryant, a Langley engineer, noticed that one of the polymers he was working with did not behave as predicted. After putting the compound through a two-stage controlled chemical reaction, expecting it to precipitate as a powder after the second stage, he was surprised to see that the compound remained soluble. This novel characteristic ended up making this polymer a very significant finding, eventually leading Bryant and his team to win several NASA technology awards, and an “R&D 100” award.

The unique feature of this compound is the way that it lends itself to easy processing. Most polyimides (members of a group of remarkably strong and incredibly heat- and chemical-resistant polymers) require complex curing cycles before they are usable. LaRC-SI remains soluble in its final form, so no further chemical processing is required to produce final materials, like thin films and varnishes. Since producing LaRC-SI does not require complex manufacturing techniques, it has been processed into useful forms for a variety of applications, including mechanical parts, magnetic components, ceramics, adhesives, composites, flexible circuits, multilayer printed circuits, and coatings on fiber optics, wires, and metals.

Thin metal lead wires use NASA-developed polymer insulation.
Medtronic’s cardiac resynchronization therapy devices use the NASA-developed polymer as insulation on thin metal lead wires.

Bryant’s team was, at the time, heavily involved with the aircraft polymer project and could not afford to further develop the polymer resin. Believing it was worth further exploration, though, he developed a plan for funding development and submitted it to Langley’s chief scientist, who endorsed the experimentation. Bryant then left the high-speed civil transport project to develop LaRC-SI. The result is an extremely tough, lightweight thermoplastic that is not only solvent-resistant, but also has the ability to withstand temperature ranges from cryogenic levels to above 200 °C. The thermoplastic’s unique characteristics lend it to many commercial applications; uses that Bryant believed would ultimately benefit industry and the Nation. “LaRC-SI,” he explains, “is a product created in a government laboratory, funded with money from the tax-paying public. What we discovered helps further the economic competitiveness of the United States, and it was our goal to initiate the technology transfer process to ensure that our work benefited the widest range of people.”

Several NASA centers, including Langley, have explored methods for using LaRC-SI in a number of applications from radiation shielding and as an adhesive to uses involving replacement of conventional rigid circuit boards. In the commercial realm, LaRC-SI can now be found in several commercial products, including the thin-layer composite unimorph ferroelectric driver and sensor (THUNDER) piezoelectric actuator, another “R&D 100” award winner (Spinoff 2005).

Partnership

Working with the Innovative Partnerships Program office at Langley, Medtronic Inc., of Minneapolis, Minnesota, licensed the material. This material has been evaluated for space applications, high-performance composites, and harsh environments; however, this partnership represents the first time that the material has been used in a medical device.

According to Bryant, “This partnership validates the belief we had that LaRC-SI needed to be introduced in (or by) the private sector: Lives can be saved and enhanced because we were able to develop our laboratory findings and provide public access to the material.”

Product Outcome

Chemical engineer Robert Bryant works with Langley Research Center’s Soluble Imide (LaRC-SI).
LaRC-SI is applied to another material in a laboratory.
LaRC-SI is an amorphous thermoplastic developed by Robert Bryant, a chemical engineer at Langley. LaRC-SI has excellent adhesive and dielectric properties and can be reformed at elevated temperature and pressures. It can be applied in the form of a spray, spin, dip coating, paint, or spread with a blade.

Medtronic is the world leader in medical technology providing lifelong solutions for people with chronic disease. It offers products, therapies, and services that enhance or extend the lives of millions of people. Each year, 6 million patients benefit from Medtronic’s technology, used to treat conditions such as diabetes, heart disease, neurological disorders, and vascular illnesses.

The company is testing the material for use as insulation on thin metal wires connected to its implantable cardiac resynchronization therapy (CRT) devices for patients experiencing heart failure, which resynchronize the contractions of the heart’s ventricles by sending tiny electrical impulses to the heart muscle, helping the heart pump blood throughout the body more efficiently.

“Our work with NASA Langley was very collaborative,” said Lonny Stormo, Medtronic vice president of therapy delivery research and development. “Our scientists discussed Medtronic’s material requirements and NASA shared what it knows about the compound’s properties as we continued our testing and evaluations.”

In March 2007, Medtronic conducted the first clinical implants in the United States and Canada of the Medtronic over-the-wire lead (Model 4196), a dual-electrode left ventricular (LV) lead for use in heart failure patients with cardiac resynchronization therapy devices.

“Through this partnership, Medtronic was able to deliver a product with enhanced material properties,” said Stormo. “In turn this helps our patients, which is the core of Medtronic’s mission.”

Placing a lead in the LV is widely recognized by physicians as the most challenging aspect of implanting CRT devices. Anatomic challenges can make it difficult to access and work within the coronary sinus to place a lead in the desired vein of the LV. The lead is specially designed for optimal tracking over a guide wire, which is intended to allow physicians greater ability to deliver the left heart lead in difficult-to-access veins.

Once implanted in the LV, two electrodes located at the tip of the lead provide physicians with options to tailor delivery of stimulation for each patient. When approved by the U.S. Food and Drug Administration, the lead is expected to be the smallest LV lead in the U.S. market.

[Source]

Polymers Advance Heat Management Materials for Vehicles

NASA Technology

For 6 years prior to the retirement of the Space Shuttle Program, the shuttles carried an onboard repair kit with a tool for emergency use: two tubes of NOAX, or “good goo,” as some people called it. NOAX flew on all 22 flights following the Columbia accident, and was designed to repair damage that occurred on the exterior of the shuttle.

Bill McMahon, a structural materials engineer at Marshall Space Flight Center says NASA needed a solution for the widest range of possible damage to the shuttle’s exterior thermal protection system. “NASA looked at several options in early 2004 and decided on a sealant. Ultimately, NOAX performed the best and was selected,” he says.

To prove NOAX would work effectively required hundreds of samples manufactured at Marshall and Johnson—and a concerted effort from various NASA field centers. Johnson Space Center provided programmatic leadership, testing, tools, and crew training; Glenn Research Center provided materials analysis; Langley Research Center provided test support and led an effort to perform large patch repairs; Ames Research Center provided additional testing; and Marshall provided further testing and the site of NOAX manufacturing.

Although the sealant never had to be used in an emergency situation, it was tested by astronauts on samples of reinforced carbon-carbon (RCC) during two shuttle missions. (RCC is the thermal material on areas of the shuttle that experience the most heat, such as the nose cone and wing leading edges.) The material handled well on orbit, and tests showed the NOAX patch held up well on RCC.

Technology Transfer

While NASA funded the full-scale development of NOAX, the sealant was actually invented by Alliant Techsystems Inc. (ATK). Under NASA funding, ATK contracted with Starfire Systems Inc., a manufacturer of polymer-to-ceramic technology based in Schenectady, New York, to supply the unique polymer material that was incorporated into NOAX.

Called SMP-10, Starfire’s polymer was designed to convert into a ceramic at high temperatures. McMahon describes, “As it heated above 1,500 °F it would start to convert over to ceramic. As a ceramic, NOAX could take much higher temperatures, allowing it to seal during the shuttle’s re-entry.”

According to Darren Welson, director of technology at Starfire, SMP-10 was formulated and processed for incorporation into NOAX, which laid the groundwork for Starfire to achieve a repeatable process for a reliable product. “Thanks to our experience working with ATK and NASA, we were able to demonstrate and test SMP-10 for aerospace, military, and commercial applications. The applications have grown and matured as a result of the ATK and NASA work,” he says.

Benefits

In looking for ways to make SMP-10 less expensive for commercial use, Starfire developed StarPCS for high temperature applications on Earth. Today, the company manufactures a family of StarPCS products for lightweight components that need to withstand extreme temperatures. “They share a common chemistry but are different based on the application,” says Welson.

The StarPCS family of products provides benefits for heat management in the military, aerospace, aviation, and automotive markets. According to the company, customers in general aviation are experimenting with StarPCS for various aircraft components.

Al Cornell, director of sales and business development at Starfire, says domestic and foreign auto manufacturers are testing StarPCS for passenger vehicles. “It can be run hotter and require less cooling than metallic counterparts. It also offers weight-saving and performance handling benefits,” he says.

Formula 1 race car
Starfire Systems Inc. manufactured a unique polymer for the sealant for the Space Shuttle. A formula incorporating the polymer is now being used in test platforms for a new exhaust management design for Formula 1 race cars.

StarPCS formulas are also being tested for heat shields in vehicles with extremely hot engines. According to the company, the material has already been qualified and is going forward for implementation for this application. “The thermal properties allow the material to be a very good insulator in race cars,” finds Cornell. “In this particular case, the composite can protect the passenger from the hot engine components.”

Specifically, Cornell says StarPCS is being used in the test platforms for Formula 1 race cars. The teams are currently looking for a new exhaust management design to divert exhaust by routing it through body panels. It would use the aerodynamic suction to pull the gases out of the engine faster and allow a 1–3 percent increase in horsepower. The problem, says Cornell, is that manufacturers have not found a way to do it without burning the carbon fiber body of the vehicle. “It’s a technology race for all the teams to get the same technology in their cars to have the same performance,” he says. “StarPCS could potentially be used for such an application.”

Auto manufacturers outside of racing are also looking for alternative materials for heat management in turbo chargers. Cornell says manufacturers want to make exhaust pipes out of something other than metal so the pipe can withstand higher temperatures. “The higher the temperature bleed, the more efficient the turbo charger,” he says. “This is the same idea as the Formula 1 application to manage an incredible amount of heat.”

Even though NASA no longer uses the innovative solution for space shuttle repairs, the Agency is incorporating SMP-10 into some of the safety components for Orion, NASA’s next multi-purpose crew vehicle.

[Source]