The iodine will "eat through" polymers other than teflon (poly ether ether ketone or PEEK). Iodine is very reactive and by reacting with the polymer breaks down the strands into shorter units causing the polymer to fail. Since different iodinated polymers are formed this will also have an effect on the physical properties of the bulk polymer making it weaker and more brittle. Glass is immune to this effect having no unsaturated C-C bonds or other sites of attack. The cotton is being iodinated as well, the the strands in cotton wool are not providing that much strength since it is only a loose packing material and you would not notice. The relevant polymer form would be cellulose and a cellulose polymer container will indead be degraded by contact with iodine.