You buy a premium pair of trekking boots or safety shoes.You keep them safely in your closet for a "special occasion."Two years later, you take them out. They look brand new.You walk ten steps. Suddenly, the sole falls apart in chunks. It looks like the rubber has turned into breadcrumbs.You didn't wear them out. Moisture killed them.Most modern shoe soles are made of Polyurethane (PU... https://cometenvirons.com/