>>9902916I'm a chemical/mechanical engineer but I work almost entirely with seals, valves, plastic protective housing etc. It sucks that it happens with a lot of the nice soft feeling plastics, Polyester polyurethane is probably the worst for it, especially in humid places.
I think it's super interesting because as you said its the migration of some liquid/oily additives like plasticizers and lubricants to the surface of the part (mixing with paint and other materials) that often makes it sticky, but a lot of those same plastics will have other additives in the polymer that react with oxygen and degrade into a similar sticky material or become ultra-brittle over time outside the packaging.
It's hard to know which factor has the greater effect given how long the process occurs over. Its unfortunate theres no way to air out figures in blisters which tend to have the biggest problems with this. I wonder if environmental factors trump both longterm though (available oxygen and other chemicals, heat, light, moisture and sun exposure). I'll install gear in Australia and it'll go way under life expectancy based on material durability estimates, meanwhile we have the same gear operating in Europe or the Arctic that's never needed maintenance.
