PBI’s use in the fire service has not been without its critics. Many older firefighters believe that the reason the number of firefighters killed each year is continuously rising is because of how good the gear works.
Back when firefighters only had a beard to protect their face, and a long rubber coat, it was rare to enter a burning building unless it was obvious that someone could be saved. Today with all the advances in gear, we go into buildings that we have no reason to go into and often stay in way to long. Before when you felt heat on your body it meant it was time to get out, today with PBI gear by the time you feel heat and pain, its too late, you’re going to get burnt or killed.
This is a fire in Susquehanna Township, outside of Harrisburg City. When we arrived on scene fire was blowing out of almost all the windows and all the floors. This picture was taken about 10 minutes into the operations when everything in the house had been destroyed. Todays modern firefighting practices, in no small part becuase of PBI, lead firefighters to these aggressive attacks. There was no one inside the house, and almost nothing to be saved, but we still made an agressive interrior attack. Several firefighters had minor injuries including Dickinson College Student Alex Hallman ’08 who fell from the top floor into the basement, he was not hurt.
The negative is not without the good. Had the firefighters tried to make an aggressive attack in the old style of gear they would not have been able to, and had there been someone inside many firefighters would have been burnt or worse.
This is a prime example of PBI gear allowing firefighters to “push the limit” and enter a structure they should not have entered. Another problem with PBI gear is that it works well to keep heat out, but also to keep heat in. Once the heat penetrates the suit, its in there and essentially cooks the person wearing it like they were in an oven. One way firefighters release the heat is by doing the “pain dance”. It looks like they are flapping little chicken wings, but it is meant to open up the neck of the suit allowing heat to be released and spread out, instead of just burning one area it makes a pins and needles feeling across the body, usually the back, chest and arms.
PBI is made through the combination of two chains, click on the image for a further explanation.
According to Wikipedia, the chemical formula of Poly[2,2’-(m-phenylen)-5,5’ bibenzimidazol] (PBI) is believed to be: ([NH-C=CH-C=CH-CH=C-N=C-]2-[C=CH-C=CH-CH=CH-])n OR (C20N4H12)n.
Because of its structure it has a high chemical and heat resistance which under “normal” conditions prevents it from burning or smoldering.
Its Heat resistance is:
continuous temperature: 540 °C (1,000 °F)
melting temperature: 760 °C (1,400 °F) under pyrolysis
retains fiber integrity and suppleness up to 540 °C (1,000 °F)
Another form of PBI called HOZOLE is being used for fuel cells and rockets because of its high resistance to heat. PBI can be both a “plastic” and a fabric, depending on the way which it is formed.
This is HOZOLE (It is the same as PBI).
The final product of PBI (in fire gear) allows firefighters to ender hazardous situations, risking their lives so others may live.
The worlds only producer of High Performance PBI fiber and polymer is PBI Performance Products Inc.
Their key product markets are protective clothing for the fire service and industrial workers, semiconductor and electronics, and various other high temperature applications.
History of PBI
1961 Polybenzimidazoles were developed by H. Vogel and C.S. Marvel with anticipation that the polymers would have exceptional thermal and oxidative stability.
1963 Subsequently, NASA and the Air Force Materials Lab sponsored considerable work with polybenimidazoles for aerospace and defense applications as a non-flammable and thermally stable textile fiber.
1969 The United States Air Force selects polybenzimidazole (PBI) for its superior thermal protective performance after a fire aboard an Apollo spacecraft killed three astronauts in 1967.
1970’s NASA continues to use PBI as part of the astronauts’ clothing on Apollo, Skylab and numerous space shuttle flights.
When the Sky lab fell to the earth, the part that survived the re-entry was coated in PBI and thus did not burn up.
1980’s PBI was introduced to the fire service, and through Project Fires an outer shell for turnout gear was developed. PBI Gold® fabric was born, consisting of 40% PBI/60% Para-aramid.
Previous to this there had been combinations of Nomex, Leather, and Kevlar materials.
Leather and Rubber fire gear left “vital” areas exposed.
PBI gear is a full suit and looks alot like a snow suit (suspender pants) with a winter coat.
1983 A unique production plant goes on-line and PBI fibers become commercially available.
1990’s Short cut PBI fibers are introduced for use in automotive braking systems. PBI staple fiber enters the aircraft market for seat fire blocking layers.
1992 Lightweight PBI fabrics are developed for flame resistant workwear for electric utility and petrochemical applications.
1994 PBI Gold fabric is engineered in black and was specified by FDNY.
2001 After the terrorist attacks on 9/11 many of the 343 Fire Fighters killed were only identifiable by their PBI Turnout Gear.
2003 PBI Matrix® was commercialized and introduced as the next generation PBI for firefighter turnout gear.
PBI replaced gear that was made of leather/rubber/or nomex. Nomex, leather and rubber are all still used but generally not without PBI. Some departments in more rural areas without the money to buy PBI turnout gear (about $2,500 per suit) still use the old style.
There are several major departments that have not yet switched to PBI becuase of tradition or fear of PBI and what happens with it. This picture is of the Chicago Fire Department, one of the last city departments to still rely on the old style of fire gear (3/4 length boots and 35″ leather or rubber coats) .
You can see in this picture that even with the boots pulled up some ‘vital’ areas are left unprotected.
Polybenzimidazole (PBI) is a burn “proof” fiber used in the protective gear for firefighters, astronauts, and other dangerous professions. This website will focus on its role in the fire service, and how its invention and use has been both beneficial and detrimental to firefighters in the United States and Across the globe.
It looks like this .
On Azom.com, a site used for material supplies, PBI is described as follows.
An infusible, polybenzimidazole (PBI) is a black high performance polymer with a wholly aromatic molecule of high thermal stability. Semi-fabricated items are made, normally by the polymer manufacturer, by powder sintering processes.
It has excellent high temperature properties – probably on balance the best of any commercially available polymer – and is very expensive. It is strong, stiff, very hard, has a particularly high strength in and recovery from compression and a CTE similar to that of aluminium. It has good chemical resistance resisting many harsh chemical environments better than many other high performance polymers, but is attacked by polar aprotic solvents and, at elevated temperatures, by strong aqueous acids and (to a lesser extent) alkalis. Despite absorbing (slowly) a high percentage of water at saturation, it is stable to hydrolysis and resists high pressure steam.
Because it is a “hard” material it is used in combination with other more plyable materials such as nomex in making firefighter turnout gear. The combination in Globe (my personal favorite and perferred brand) is 40% PBI 60 % Kevlar (for rip protection and binding). (http://www.globefiresuits.com/globe/materials/outer-performance.asp#pbimatrix).
