Almost all plastics are hygroscopic and will absorb the coolant to some degree making dimensional accuracy problematic.
I'm not 100% sure about that.
I think the problem is that even in industry that people think of "Plastic" as one class of "material", whereas there is a vertiable zoo of polymers and copolymers with different formulations and associated processes that can have dramatically different physical, electrical and chemical properties.
Hygroscopic VS Non-Hygroscopic Resins
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Plastics Technology
^^^ Useful link
Hygroscopic vs. non Hygroscopic resins...
Hygroscopic Resins
E.g. Nylon, ABS, Acrylic, Polyurethane, Polycarbonate, PET, PBT,...
^^^ These will absorb water vapor and if in a low relative humidity environment will give up their absorbed water vapor causing dimensional changes as internally absorbed water migrates to the surface.
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Non-Hygroscopic Resins
E.g. Polyethylene, Polypropylene, Polystyrene, PVC
These polymers are not completely hydrophobic (like a wax) but only
adsorb water vapor to their surface.
Polypropylene in particular is used in medical applications for vials and storing liquids , same in the food industry.
Polypropylene - Wikipedia
Interesting all the variants of polypropylene including more crystalline formulations.
Hard to say what with all the different components used in coolnats for machining what further effects that might have on various polymers.