In low surface area materials this much variation should not happen.  Please make sure that sample was degassed properly in both the analysis with same degassing condition and one more thing, the weight that you have taken is correct. Most of the time the error in surface area come because of the wrong weight entered during analysis.

If you would share the isotherm image then it will be convenient for people to understand the problem. I hope it would help you. If you need further help, please feel free to ask.

With kind regards

raeesh

Were both numbers a result of the same analysis method? Different models can yield results with some discrepancy. Please provide more info about.

Dear Dr. Can:

It is possible that answer behavior depending on the kind of polymer and origin of the sample.

There is a small number of information about the phenomenon. It is possible a great number of answer and some of them can be in the reality misbehave. In fact, see only the number of the surface area is only a partial way, it is very import have access to the curve of Adsorption hysteresis and pore size distribution. Furthermore, a good surface morphological characterization based on the Scanning Electron Microscopy. As ist, it is possible suppose, distinct mass, changing of surface during processing, fail in degassing step of sample analysis, involuntary surface exposition to kind of solvent, adsorption of water vapor or gas, etc...etc..., distinct materials submitted to distinct level of mechanical work...

Some other kind of contamination can be taken place if after extrusion you use water and additive to clean and wash the polymer fiber or block; as a function of time the medium can be stay satured and further crystals can be attached to the surface. Also, powder from air atmosphere can be attached to surface. Obviously, with a minor effect under the BET area.

Kind regards

Marcos Nobre

In low surface area materials this much variation should not happen.  Please make sure that sample was degassed properly in both the analysis with same degassing condition and one more thing, the weight that you have taken is correct. Most of the time the error in surface area come because of the wrong weight entered during analysis.

If you would share the isotherm image then it will be convenient for people to understand the problem. I hope it would help you. If you need further help, please feel free to ask.

With kind regards

raeesh

Thank your for all kind answers. I have attached BET reports of polymer for your inspection.

Dear Mustafa,

There seems some problem with your isotherm. It is not possible that dosorption comes below adsorption line. So i would suggest that if this instrument is in your lab  please run the standard alumina sample to see the accuracy of the instrument and the shape of isotherm should be exactly matching with the isotherm of the standard sample given in the booklet of standard sample. Otherwise contact the service engineer of micromeritics.

With best regard

raeesh

Dear Raeesh,

Thank you for your valuable answer. I'll contact intrument's expert.

Regards.

Dear Dr. Can:

From PEHA file the single point measurements was carried out being the routine of degassing accomplished, as indicated at protocol.

From PEHA1 file a fast adsorption/dessoption measurement was carried out exhibiting further evidence of absence of the stage of sample "degassing". Such procedures should be further considered in the measurements protocol. This stage typically is or have a mechanic control, is necessary an operator since temperature set up can decompose the sample. In the masthead of PEHA file there is evidence for that Degassing procedure uas performed, with all set of measurements.

Vapor and gases adsorbed under samaple surface is the major cause of anomalous phenomenon mentioned by the Dr. Muhammad, the branch of the isotherm ascribed to dessorption, as a whole is shifted of proper position.

Kind regards

Marcos Nobre