I have seen a lot of materials eg. cellulose, having peaks upside and downside in different papers (irresepctive of the unit being %/C or %/min) though they share the same peak position. Can anyone tell me reason? Is it done by inverting the sign before the values prior to plotting of the graphs? If it is so, why is it done?
Do you mean differential thermogravimetry? Usually in DSC at same position the peak in different paper remains upward or downward primarily bacause of polarity of detector. If it isDTG you are getting up or down due to polarity of measurement unit. You may check the Y-axis scale (+ or -) . You will feel the meaning of up or down
I think negative value of DTG may indicates the loss of Mass (%/Min) with respect to temperature.
Hi, Can you refer the DTG curves? Or can you be more specific about X and Y axes and their units/scales, what are they represent (% of time/temperature/weight)? I suppose the peaks are the corresponding temperatures of sample's weight loss/weight gain percentage. Generally, the TGA curve shows weight loss/gain in declining/increasing fashion compared to the horizontal / platue region; and it's corresponding DTG curve will show you the peak temperature and percentage change of sample's weight.
I know i am replying 4 years late but i wanted to leave this answer here if anyone finds this question.
I believe that the DTG curves should have negative peaks if there is a mass loss and positive peaks if there is a mass gain. Because simply we can get the DTG data from (%TGA(2) - %TGA(1)) / (Time(2) - Time(1)).
The time always increases so the denominator is always positive. if there is a mass loss, the numerator will be negative and the peak will be negative and vice versa.
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