Using AutoSorb iQc (BET - gas adsorption ) in the determination of SSA and pore size of powder materials a first step is out gasing which is done under ultra-vacuum and high temp. of about 300C, does the step is needed for polymers also ?? if yes ... then for what temp. ? and how long ?
Outgassing is needed to remove adsorbed and absorbed gases and water by a combination of vacuum, heat, and purging with an inert gas. This should be done at the highest temperature possible in order to reduce the outgassing time. However, the temperature must not be so high that it changes the structure of the sample (20 degC< Tg < ½ melting point). http://www.ivtnetwork.com/sites/default/files/IVTGXP0712_062_Olson_Peer%20Review.pdf
The last page of the Belsorp MAX users manual describes very thoroughly recommendations for degassing.
I cannot share the manual itself here, but try googleing "belsorp max pdf". There you will find a table with temperatures and remarks for many adsorbents (active carbon, zeolite, polymer, alumina, silica, titania, calcium carbonate and cement).
When desorption-adsorption degassing method is employed, the temperature and time of degassing depends on what is the expected surface area and other properties of material. It is necessary to avoid affecting the nature of the surface of the sample when degassing process performed at high temperatures. When heating is done, the temperature and time of de-gassing are as low as possible to carry out measurement of specific surface area in a suitable time
I frequently outgas my samples at room temperature.
I judge the effectiveness by watching the achieved vacuum and since I am usually not in a rush, I let the sample be evacuated for at least 12 hours.
As long as you reach a low enough vacuum and don't detect "significant leak-rates" (pressure increase when you close the vacuum valve); you should be OK.
All of it will depend on your sample. If the sample has very small pores, the outgassing will take longer and may require some elevated temperature.
ISO standard 18757 provides some guidance on this. I can send you a copy if needed, but I am not sure, if I am allowed to post a copy here.
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