while casting a carbon filler /polymer composite membrane on glass, during inversion in water , it gets up with a convex surface which is a little shiny. is this side the top surface of the membrane? reasonably the side which is in contact with the glass substrate should be more flat and shiny but it is not and the air- surface gets like this in water . and it looks a little darker with the filler, than the bottom side... bottom side looks whiter? why does that happen???
thanks
yes that makes sens thanks . but I do not know for what reason the top side is more glossy like and shiny... because usually when a surface is in contact with a flat substrate like glass it is more flat and smooth so it is expected it becomes more shiny but it is exactly opposite ....do you think it is because of the pore sizes and the reflection effect of the light together?!
Seyede,
I have worked on Polymer Nanocomposite Membranes prepared by Phase Inversion methods. I found the same observations. Please see my article below:
Article PEG-CNTs nanocomposite PSU membranes for wastewater treatmen...
and
http://onlinelibrary.wiley.com/doi/10.1002/app.44688/full.
Dark Side:
The reason for darker top surface was the filler migration from bottom to top surface during phase immersion process as the the filler was hydrophilic in my case. Thus, higher contents of filler on top surface.
Glossy Side:
The bottom surface has open and larger pores so reflection is not effective. However, the top surface possess thin layer with small pores which could lead to greater light reflection.
I hope to answer your queston.
it happens because of gradient of filler concentration. The air-side always contains more polymer - that's why it is glossy. It is easy to prove it by measuring the ATR spectra of both the sides. You'll see that the IR-bands of the polymer are substantially stronger on the air-side.
Best Regards,
Leonid.
Thank you dear Arsalan and Leonid. so to sum up out of your answers together, is it correct to conclude that the top surface (active side) is more glossy since more polymer is found exactly on the top surface in comparison with the bottom surface and also it is darker because more filler is found near the top surface (I mean not roughly on the surface because we are saying a lot of polymer are already located there)rather than near the bottom surface ??
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