That’s right, the two things that make human life possible—water and air—are killing our shoes. Their role in degrading polyurethane can be attributed to the chemical processes of hydrolysis (in the presence of moisture) and oxidation (in the presence of oxygen). Simply put, the humidity in the air, and, yes, even the air itself, seeps into the PU and, slowly but surely, breaks it into itty-bitty sticky pieces. Delve deeper into the subject, and the news only gets worse. Bottom line: Pricy collectables shouldn’t be made out of PU.
“Both mechanisms—hydrolysis and oxidation—are accelerated in foam polyurethane,” says Northwestern chemistry professor SonBinh T. Nguyen. “Both of these mechanisms are also accelerated at higher temperatures, and oxidation is further accelerated by light. Mold growth is another degradation mechanism. This is a fairly common phenomenon.”