Zylon
Zylon is a trademarked name for a range of thermoset liquid-crystalline polyoxazole. This synthetic polymer material was invented and developed by SRI International in the 1980s and manufactured by Toyobo. In generic usage, the fiber is referred to as PBO.
Zylon has 5.8 GPa of tensile strength, which is 1.6 times that of Kevlar. Additionally, Zylon has a high Young's modulus of 270 GPa, meaning that it is stiffer than steel. Like Kevlar, Zylon is used in a number of applications that require very high strength with excellent thermal stability. The material has been used in body armour, in tennis racquets, table tennis paddles, and in snowboards, in various medical applications, and in some of the Martian rovers.
Usage
Body armor
Zylon gained wide use in U.S. police officers body armor protection in 1998 with its introduction by Second Chance Body Armor, Inc. in its "Ultima" and "Ultimax" protective vests. At least as early as 2002 August, Point Blank Body armor offered "Fusion" and as early as October, it offered "Legacy". Armor Holdings's Safariland offered ZERO-G Platinum as its Zylon option, and oldest brand, its very own American Body Armor, had its most premier option also made with Zylon. Zylon body armor panels sometimes cost twice as much as Kevlar or 35% more than other advanced materials. Despite "sticker shock", the marketing for Zylon body armor described incredibly low weight and thickness, but shockingly high protection, causing some to refer to it as a "miracle fiber".The incident and the aftermath
Protective vests constructed with Zylon were questioned after June 13, 2003, when Oceanside, California, Police Officer Tony Zeppetella's and Forest Hills, Pennsylvania Police Officer Ed Limbacher's vests both failed, leaving Zeppetella mortally wounded and Limbacher seriously injured.On Sept 15 2003, Second Chance's president and CEO wrote a letter about Zylon and what his company's position about Zylon, and what their reaction was going to be. He started by stating that the ULTIMA line had 30 "saves". He described two years of testing "200 ULTIMA vests from 37 different agencies in 19 different States".
He then said "Unfortunately, for all involved these results indicated the unexpected decrease in the ZYLON fiber strength. ZYLON fibers in various forms are used widely within our industry. Although inconsistent, these results have led us to where we are today. ULTIMA and ULTIMAX vests, as you know them today, have been discontinued from our product line."
The company would offer a "Performance Pac" to "account the worst-case performance scenarios of used, in service vests", for free.
Stephen Croskrey, President and CEO of Armor Holdings Products Division put out a letter as a reaction to the statements by Second Chance. In the letter, the CEO states that he found the "unexpected decrease" statement by Second Chance to be vague. He then said his company and Toyobo tested the material regularly, and that it was degrading at a rate typical compared to other materials. Finally, he stated that for his company, all incoming lots of materials had some tested, and they regularly received used vests to test.
The realization and end to Zylon's use in body armor
Some studies subsequently reported that the Zylon vests might degrade over time and leave their wearers with less protection than expected. Second Chance eventually recalled all of its Zylon vests, which led to its bankruptcy. The company was once able to claim that it held over 50% of the market for law enforcement body armor, all by itself. This explains why 98,000 vests were recalled by Second Chance alone. Comparable vests cost as much as $1450 at the time, or over $2100 at the end of 2014.In early 2005, Armor Holdings, Inc. recalled its Zylon-based products, and decreased the rated lifespan warranty of new vests from 60 months to 30 months. In August 2005, AHI decided to discontinue manufacturing all of its Zylon-containing vests. This was largely based on the actions of the U.S. government's National Institute of Justice, which decertified Zylon for use in its approved models of ballistic vests for law enforcement.
The United States Justice Department launched numerous investigations into possible violations of the False Claims Act regarding the defective vests. Throughout the course of litigation, settlements totaling more than $136 million were reached with 18 entities involved in the production and sale of Zylon vests. The investigations concluded after nearly two decades when the final settlement was obtained with material supplier Honeywell International in late 2022.