What you are looking at is a set of Hatch knee pads and elbow pads. Every square inch of the hard shell polymer is decomposing. The nylon fabric is completely unaffected and nylon straps are unaffected.
A polymer is a single chain molecule which when exposed to heat and humidity becomes a smorgasbord for fungus and bacteria. The nature of bacteria is such that they will metabolize anything, so polymers in tropical environments do not fare well; requiring meticulous attention. If you are working along the Equator and subtropics you’ll want to pay close attention to avoid what you see in the photo.