With regard to inner sleeves, plastic polyethylene is purported to be better than the common paper sleeve and less bulky than the poly-lined paper variety.
The intermediate polymer, known as a poly (amic acid), is soluble because of strong hydrogen bonds to the polar solvents usually employed in the reaction.
For example, even though meat is held under refrigeration or in a frozen state, the poly-unsaturated fat will continue to oxidize and slowly become rancid.
