Which famous adhesive product was initially considered a failure because it wasn't strong enough for its intended industrial purpose, but later became incredibly successful as a consumer product?

Throughout history, many revolutionary products we use today weren't actually created for their current purpose. Some of the world's most successful inventions were the result of experiments gone wrong, mistakes, or happy accidents. This trivia explores one such famous product that transformed an industry despite being an initial 'failure.' Test your knowledge about these serendipitous discoveries that changed consumer habits forever!

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Post-it Notes (developed by 3M when Spencer Silver created an adhesive that wouldn't permanently stick)
Super Glue (discovered by Harry Coover while trying to make clear plastic gun sights during WWII)
Scotchgard (invented accidentally when a 3M researcher spilled a compound on her tennis shoes)
Velcro (created when Georges de Mestral noticed burrs sticking to his dog's fur after a hunting trip)