Hi, 

http://en.m.wikipedia.org/wiki/Polyethylene_terephthalate

Lavsan material (the link above) can be useful fot you as a infrared transparent plastic

Vlatcheslav,

Thanks for the suggestion. A very quick search of few literature references indicates me that Lavsan (PET) fibers might be a good candidate. But other publications indicate a very complex absorbance signal in that region for generic PET. Do you have experience with IR properties of Lavsan?

Your question is not clear to me. Do you mean to analyze crystalline silica or crystalline silica on PVC filter. If you want to analyze just silica, you don't want any other polymer to interfere your analysis. In such case, remove the silica from the filter and sandwich it between two KBr or NaCl discs. You can place this sandwich directly under the IR beam and record the signal only from silica sample. Alternatively, you may crush your silica sample with KBr powder and make a pellet for the analysis.

PMMA

Atul,

I'm sorry if the question was not clear. I need and want analyze crystalline silica when it is deposited on PVC filters. That is needed for my application. I'm full aware of the us of KBr and NaCl discs for powder material.

Alexander - thanks, I will look into PMMA

Hello Emanuele,

Yes, I was working with lavsan at a wavelenght of 800nm and it was not absorbing light almost, i.e. conferming it's transparency. Unfortunately I cannot provide you with it's transmittance coefficient now, can you wait for 10 days? I will be back at the laboratory in 10 days. 

Viatcheslav, I can absolutely wait 10 days. Thanks fort the help

That's good, I will send you the transmission data for the wavelenght range of 600-1000nm.

Dear Emanuele,

I have performed the transmittance measurements of lavsan with the thickness of about 0,25mm in the spectrum range of 700-1100nm (I have just noted that you was asking about the range of 600-1000nm, if it is needed I can measure from 600nm). The transmittance measurement revealed a high lavsan transparency about 89% in the range of 700-1100nm.  The results of the measurements are attached.

Kind Regards,

Viatcheslav

Viatcheslav,

Thanks so much for this information and chart. No, no need to go down to 600. What I find interesting is the fact that lavsan has a very flat spectrum with minimal absorbance. 10% would be ideal. For my application the layer needs to be much thicker. I wonder if few mm of lavsan will reduce drastically the IR intensity. Any idea?

I think a few mm thickness lavsan will reduce the IR intensity drastically. My assumption is about of 40-50% transmittance for a 1mm sample.

Thanks Viatcheslav, it is a good start for me! I really appreciated your help.

It was nice to be helpful for you.