This source lists polypropylene as suitable for use with NaOH.
However, this paper seems to demonstrate that NaOH slowly degrades polypropylene (even at fairly moderate temperatures).
Does anyone know more about this? Would anyone know for instance what it could degrade into (potential for trace contamination of the NaOH solution)?
There is a small possibility that some of that information is described in the body of the paper, but unfortunately I only have access to the abstract.