When analysing the crystallinity of Kevlar with XRD we find it difficult (almost impossible) to calculate the amorphous phase of the polymer.
Should it be done by a fitting software (Origin, Matlab…)?
Is the amorphous peak located in a specific angle (2theta) or it shifts from one type of Kevlar to other?
Please find attached a spectrum of Kevlar with its characteristic peaks.
Thank you so much
This is what the 2D diffractogram for Kevlar looks like compared with an Aluminum foil "standard". To do this correctly you must consider the entire 2D diffractogram and not just an antiquated lineal equatorial scan diffractogram using a 0D pre-historic Geiger counter. The difficulty you and most XRD users still addicted to the 0D "pacifier" have is the neglect of the rich 2D XRD data ever present in each of your observations. You are trying to interpret precise Nano structural details from just a sliver of the 3D reciprocal space data present in most XRD observations.
Tell us more about your experimental conditions, sample preparation and morphology when convenient.
Thank you very much for your answer.
The reason for performing the 0D scans is that we don´t have the option of measuring in 2D. I thought that maybe we could obtain some information about the crystalinity of the samples this way.
We use Kevlar fibers from a life vest (10 micrometer diameter and 4-5 cm length) and we put the sample (4-5 mg) in the Xray diffractometer with no pretreatment or special preparation.
Thanks again
Ana
I dont know much about XRD but I do know alot about liquid crystal polymers, like kevlar. It could be because you're using a fiber thats been drawn and oriented to the point where its completely crystalline.
Ana! "The reason for performing the 0D scans is that we don´t have the option of measuring in 2D." Really! Ever heard of the extinct photographic film? The "2D detector" since the Braggs, Ewald, Laue or Guinier. Certainly try it and use a conventional "scanner" to digitize. Find an old dentist in your neighborhood and comandeer the entire supply if you can :-)
XRD is the only know method (to me) that'll accomplish your objective. You could also "spin the sample during the measurement" as practiced conventionally but you impart the universal "smudge factor" to the XRD data and lose the perspective of "preferred orientation" thus. I'm not sure how one deconvolutes the proprtion of amorphous to crystalline componnets in that manner.
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