I am doing an experiment coating polyester foams and I need to freeze dry them. I put the foams immersed/squeezed in the coating solution in small test tubes in the freezer at -30 for 48 hours and then attached them in the freeze dryer, but it doesn't seem to work. The samples are very small like 1x 1 x 1 cm. I am thinking maybe it's an issue with the pre-freezing step? Also, how do we find the eutectic point of the samples? Thanks!
can you freeze dry from benzene? In my polymer science days I would:
1. dissolve polymer in benzene
2. freeze vial in liquid nitrogen
3. place vial in vacuum oven
4. pull ultrahigh vacuum on oven, with liquid nitrogen trap placed in vacuum line between oven and vacuum pump
Overall dipping the vials in liquid nitrogen in frozen is the freeze step in freeze drying. The vacuum you apply has to be strong enough to sublimate so much frozen solvent that the energy of sublimation keeps the sample frozen.
But if I dissolve the polymer in benzene I would lose the porous structure of the foam no?
What are the solvents that you are using? What is the freezing point of the sponge and solvent mixture? Do you have a freeze dryer that can freeze the sample on a shelf? What is the temperature of the cold trap and shelf of the freeze dryer?
The properties of the sample and the capability of your freeze drying equipment are critical factors in answering this.
Kind regards,
Rob
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