Which failed product innovation accidentally led to the discovery of Super Glue (cyanoacrylate adhesive)?

Innovation isn't always a straight path to success. Some of history's most famous inventors and companies have experienced spectacular product failures that ultimately reshaped how we think about product development. This trivia question explores one particularly infamous product failure that actually led to an unexpected discovery that revolutionized an entirely different industry. Test your knowledge of how failure sometimes leads to innovation!

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A transparent gun sight material being developed for WWII sniper rifles
A heat-resistant coating intended for NASA's Apollo spacecraft
A non-stick kitchen pan coating that wouldn't adhere properly
A waterproof fabric treatment for military rain gear that became too rigid