2 hours ago, kenny1999 said:

Plenty of such information if you simply do a search on Google with keywords, "water absorption rate polypropylene".

One example:

https://omnexus.specialchem.com/polymer-properties/properties/water-absorption-24-hours#Values

 

Ah OK, but for materials like polyethylene and polypropylene these are very low values, 0.01% or so. 

The reasons for some solvents to be able to get into the structure of polymers is because they are generally not fully crystalline, due to things like irregular chain branching that make it impossible to get perfect packing of the chains in the structure. So you get some voids, into which small molecules can go. There is more abut it here: https://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Polymer_Chemistry/Polymer_Chemistry%3A_Morphology/Polymer_Chemistry%3A_Polymer_Crystallinity   

 

3 hours ago, exchemist said:

Ah OK, but for materials like polyethylene and polypropylene these are very low values, 0.01% or so. 

The reasons for some solvents to be able to get into the structure of polymers is because they are generally not fully crystalline, due to things like irregular chain branching that make it impossible to get perfect packing of the chains in the structure. So you get some voids, into which small molecules can go. There is more abut it here: https://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Polymer_Chemistry/Polymer_Chemistry%3A_Morphology/Polymer_Chemistry%3A_Polymer_Crystallinity   

 

I think those water absorption values are not about the perfectness of the surface of the materials. It's like for the most inert compounds, there is no actual zero reaction rate, but the reaction is going to be extremely slow which makes it virtually unreactive.

What will you guy do if you find dead bodies of household pests e.g. roaches, flies, left on your ceramic or stainless steel dish plates? For some reasons I left home so urgently and had no time taking care of the hygiene, and only came back after about a year.

What I can think of now is to first rinse with dish-washing detergent and water and then rinse with boiling water. Anything else I can do more to clean up these dish plates?