Dear colleagues,
I am working with polyamides, and of course the properties of these depend a lot on their moisture content. This is why you usually investigate the materials both dry and conditioned, that is to say, with their equilibrium moisture content. If you don't want to wait for months before each test, you will have to perform some kind of accelerated conditioning, e.g., place the samples into hot water for a certain amount of time, in order to get to this moisture content.
However, the moisture won't be distrubuted uniformly within the samples after such conditioning: the surfaces will be more moistured and the core will be rather dry. I'd like to measure this nonuniform moisture distribution after various conditioning procedures, but I wouldn't know how to. Is there any established technique for a measurement like that?
Best wishes,
Dietmar
I do not support a test for the moisture content by placing a polyamide over a hot water bath for a specified time. A temperature above 100 oC is required to remove water from the polymeric sample taking into account that polyamides have high melting point.
My suggestion is to do the test on two samples of equal masses. The first "wet" sample (as it is) will be placed, on a watch glass, in an oven at 103 oC for half an hour & then weighed. The percentage moisture is calculated.
The second "wet sample" is pulverized into a powder & then repeat the above at same T and for same duration.
Comparison will reveal if there is distribution of moisture within the polyamide.
Hi Dietmer,
There are many moisture meters out there but I have not come across a device that can automatically measure moisture distribution as you desire.
I suggest destructive analysis (I presume your polyamide samples are bulky in size, I mean non-particulate) whereby you cut through a section (longitudinally or across or both, as the case may be), measure and record the moisture contents at various locations in order (preferably starting from the more dried inner-central part to the wet outer part). Analysis of the data by plotting or otherwise would give you the desired (longitudinal or cross sectional) distribution.
Moreover, if the samples are fused particles in form of cakes, make use of moisture meters with needle-like detectors to access the inner regions of samples if possible (otherwise, return to the destructive means).
Note: conventional drying to constant mass method can as well be used in the absence of the meter but then, you would need to take samples out of your SAMPLES.
I hope this would be helpful.
Regards
Dear all,
Thanks for your suggestions. For now, I chose a rather simple method, i.e., cutting samples out of my sample, as Onyeka suggested. This is not very precise, as you cannot really manufacture samples smaller than 1 mm in size, but it at least gives you an idea about the difference between the outer 1 mm and the core 1 mm. The results are useful and we can work with that. Nevertheless, it would be nice to find a more sophisticated method as well.
Regards, Dietmar
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