The problem with vacuum drying is not so much the boiling point of water as in an unimpeded environment, those values are: At 25" Hg : 56C, 27" Hg : 45C, 28" Hg :40C, and so on.  The problem is degree of impediment caused by the actual plastic.  To build off what Yuan-chia Joyce Koo has stated but with a different vector in mind, the plastic material of moisture bags for instance is highly resistant to diffusion.  Different polymers will follow accordingly.

For information, many plastics must be dried immediately prior to molding otherwise they suck up moisture like a sponge. Common hygroscopic polymers are Nylon, ABS (Acetyl Butyl Styrene), PC (Polycarbonate), and PMMA (Poly (methyl methacrylate)).  Nylon and PMMA are very common materials in component shells.  ABS and PC index* at temperatures not much higher than boiling water and are not typically used.  PP (Polypropylene) and PE (Polyethylene) are not so bad, hence their use in capacitors, but these index in the 200C range making them a bear for SMT placement.
My general rule is the higher the MSL number, i.e., the more likely a part is to absorb moisture, the easier it is to dry.

For normal bake (NO vacuum), here is the formula I derived several years ago:
Thickness (mm) X Thickness (mm) (Divided by) Bake Temp Factor 
D125oC= 0.4427 // D90oC= 0.1270 // D40oC= 0.0131, Result is time in hours.

I have never experimented with Vacuum Acceleration, but I will query the Penn State Plastics Engineering group with what we are trying to resolve and post those results to the J-STD-033 committee as well as here.
* Index is the temperature at which a plastic flows well enough to be molded.  It is neither solid nor liquid, but soliquid.

This all sounds like a job for Clumpy and Kloumpios when they are next available.