Zylon
Zylon was an incredibly high strength material that was useful for use in body armor, but that after studies found it's faster than ordinary degradation due to environmental factors was pulled from the general market. Zylon has a number of advantages over materials like kevlar, being approximately 1.6 times stronger, or having 5.20 GPa compared to 3.0 to 3.6 for kevlar. It also has a higher velocity and fiber fracture resistance, at 813 m/s vs. approximately 600 m/s for kevlar. While kevlar can be more easily penetrated by high velocity rounds such as the 5.56mm, Zylon can stop the rounds much more easily due to it's higher velocity resistance and strength. Zylon is also significantly more heat resistant, at 650 degrees celsius (1200 degrees Fahrenheit) in comparison to kevlar at under 160 degrees Celsius (320 degrees Fahrenheit). However the material notoriously broke down quickly due to environmental factors, specifically water, and the lifetime age was reduced from 60 months (5 years) to 30 months (2.5 years), and was pulled from the civilian market after NIJ tests showed a degradation of strength much more quickly than anticipated. However if protected from water and other environmental factors, the armor is able to provide the same high strength for much longer periods of time, and therefore more viable. When combined with various treatment processes and an NBC suit, the armor is well protected from the environment, and thus can easily be used in situations the original Zylon armor could not.

The armor is almost combined with ,known as "liquid body armor", which hardens under stress and increase the strength of the armor. In testing approximately 4 sheets of kevlar could perform as well as 14 sheets, making the armor approximately 3.5 times stronger. It was more resistant to higher velocity impacts, as well as sharper weapons and projectiles, and more resistant to repeated impacts in the same spot. When combined with zylon armor it's approximately 5.6 times stronger than kevlar, and can stop high velocity projectiles. With a hard piece of material on the outside of the armor, it helps break up and fragment the round before passing in to the armor below, like with an EOD suit or air chamber glass.

https://www.nij.gov/topics/technology/body-armor/pages/results.aspx

https://stuff.mit.edu/afs/athena/course/3/3.91/www/slides/cunniff.pdf

https://en.wikipedia.org/wiki/Zylon#cite_note-5