In order to calculate the crystallinity of a polymer nanocomposite, I would like to use XRD. But it is difficult to deconvolute the XRD pattern coming from crystallin part and amorphous part (which is a very broad peak that I have no idea about its position in 2theta, neither its FWHM) of the nanoparticle filled polymer. Do you have a reference for these kind of deconvolution? Is it possible that, the nanofillers can hide the signal coming from either crystallin or amorphous part?
Hi Atilla,
does the polymer itself has a known reference pattern for its crystal phase? If the unit cell data are known that's something that could help you in fixing the crystal phase parameters and work on the amorphous part. What is the nature of your nanofiller, and at what concentration is it present? I deal with very poorly semi-crystalline polymer at times and having reference data for the crystalline phase helps fixing some parameters. If those data are not available for your polymer, you could try annealing it to develop some crystallinity and record your own reference pattern.
Bonjour Pierre,
Thanks a lot for your reply.
That is what I did as my polymer has a known crystal structure. But the crystallinity that I found by XRD doens't fit with the calculations from DSC. I then concluded that, one of the methods that I used is not correct although there is an explanation. I keep in mind that DSC and XRD techniques have different principles. This brings us to the second part of my question : can nanofillers shadow the XRD signal from polymer?
You're welcome Atilla,
we've also observed that DSC and XRD don't always agree, sometimes due to crystallite size making it harder on the XRD, other times due to enthalpy reference values for pure crystal compound for DSC. As to whether the nanofillers could obscure the XRD signal from the polymer I imagine this could happen if the nanofiller scatters particularly well and if it's present in large concentration. Can you use the X-ray pattern of the nanofiller by itself as a guide in your peak decomposition procedure? Does it show some sort of crystallinity by itself?
Hii Pierre,
Thank you for your reply. I wanted to test first the deconvolution procedure on virgin polymer.
How can you explain the difference in crystallinity calculated from the DSC and XRD that you refer? This can not only be the problem of enthalpy reference.
Hi Atilla,
I agree, it's just one of the possible parameter that could explain a difference. Consider also that XRD analyze the polymer at room temp vs. at more elevated temperature for DSC, and possible crystal phase transition in the polymer may have an impact on crystallinity value. If there is preferred orientation in your polymer, you'd need to randomize it before doing XRD.
Hi! two comments, a) please remind that sometimes the nanofiller can induce crystallization on the DSC. Did you notice any peak before your melting peak? b) when calculing the Degree of Crystallinity of the nanocomposite by DSC you should consider that you are not having a "pure" matrix, si you can not simple divide your enthalpy divided by the reference entalpy, you need to divide also by (1- Xc) being Xc the concentration of your nanofiller.
Hii Jon,
Thank you very much for your comments.
I don't have any peak before melting peak.
I know that the crystallinty should be calculated with respect to the amount of polymer who exists in the nanocomposites.
Even all these comment, I did not understand why I find the different crystallinity between XRD and DSC results. Probably Pierre is right, saying that we don't probe the same things by these two methodes.
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