Powder

I once had a super comfortable office chair. After more than 10 years of use, it had finally reached the end of it's lifespan. Since it was basically the perfect chair, I wanted to find out the exact name of the model to get a replacement.

The back of the chair could be opened via a zipper. Opening the chair however released quite a bit of white powder. At first I assumed that it was just flour. It definitely wouldn't have surprised me if that was the secret to the chair's comfiness. That's when I noticed how there were also pieces of white fabric mixed in. The fabric held it's shape and could be held, but as soon as pressure was applied, it basically disintegrated.

So in conclusion, fabric can deteriorate even without direct sunlight and or contact.