I know you can influence crystallinity during produciton but can it still be influenced aftwards?
Ball milling, or grinding in a McCrone mill (with a suitable solvent) for long time periods should reduce crystallinity.
Thank you for your quick reply Henry J. Spratt ! So its one strategy to reduce the particle size, or would the milling/grinding process also increase the amorphous structure in the material? We are aiming to decrease the crystallinity of post-consumer PET for easier degradation.
Vanessa Srebny excessive milling will reduce crystallinity/increase amorphous content, in addition to lowering the particle size distribution.
@ Henry J. Spratt regarding your comment on the McCrone mill: The McCrone mill was initially designed to have a low impact on the crystallinity to receive a fine grained powder with as high as possible crystallinity.
But in general, yes, milling helps. Not sure if in the case of PET heating helps as well?!?
Robert Möckel yes, but leave anything in there for long enough with a hard enough grinding media, and you will reduce crystallinity. In general < 10 min will not impact crystallinity / any impact is preferable to not micronising. e.g. Reference: X-ray Spectrometry, (1980), vol 15, p. 267-270 clearly shows amorphous content increases for quartz with 20 min of grinding compared to 10 min and less.
@ Henry J. Spratt yes, absolutely true and thank you for the reference. On the other hand quartz is known to likely react to stress by recrystallization easily, therefore quartz might be not the perfect example here (I have seen a reference for that some time ago, but cannot find it right now). My point here was that there are more suitable mills available for "producing amorphous content" than the McCrone mill :-)
According to some grain size distribution tests, we mill our samples for 12min, which works perfectly for routine analysis. BUt I must admit that we tend to overestimate amorphous contents, although I think it's rather because of the XRD device producing bumps in the low 2theta range (
Dear all, post-production means after PET production (synthesis) or it means post-processing, i.e., after forming PET products such as bottles for exemple. If it means Processing', quenshing (abrupt cooling) is the technique used to rapidly block crystal growth of polymers have high tendency to crystallization. Now, for the milling technique, even if it is efficient in reducing the degree of crystallinity of the PET powder, this latter will regain high crystallinity once melted and cooled (if gentle cooling) again. My Regards
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