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+ Polymer chemistry
+ Degradation
+ Characterization techniques
+ Polymers
+ Tga
+ Thermal stability
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Judas Matete

How can I interpret a TGA graph?

Aliayson  Follow

The given polymer, and composite materials, can be subjected to various thermal conditions during their processing and applications. This necessitates the understanding of their thermal characteristics. The thermal degradation behavior of the composites was experimentally explored by using a Thermo-Gravimetric Analyzer under atmosphere nitrogen.

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Colin John Cook  Follow

You have to read following key parameters in TGA: The atmosphere in which your reaction is taking place, i.e, air, nitrogen, oxygen etc.,
IDT (or onset): Initial decomposition temperature is the point where your material starts disintegrating and is the measure of thermal stability of that material.
MRDT: maximum rate of decomposition temperature- shows the regime when the maximum component in your material is decomposing. 
D1/2 (or d half): is the temperature when 50 wt.% of your material has decomposed.
FR (final residue): the amount left after the end of the heating, as it gives the final composition of the material.
The area under the derivative curve qualitatively determines the amount of that component decomposed.
From your curves, in both cases, area under the main decomposition stage is very close (or similar), it means that similar amount of that component  is decomposing as a function of temperature. However, the rate or mode of decomposition has changed after irradiation. The decomposition of first component is less, probably because that particular component has evaporated between your steps. More importantly, the IDT has significantly decreased from 275 to 247 C while residue remains same (very close). It may be alarming depending on your application. For example, high-performance application needs increased IDT while lithography or drug delivery needs decrease in IDT.
I would recommend you reading my attached papers for better understanding of this technique.
Good luck!

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David Jones  Follow

It is better to base the analysis on the DTG curve than the TG. However, it is worth remembering that parameters obtained on the basis of the TG and DTG curves are lumped parameters, which values lump many different factors. Deconvolution of the DTG curve can sometimes help to obtain results having physical meaning.

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Curt Weinstein  Follow

For the interpretation of TGA thermograms, find the percenatge weigt loss of compound and predict the major difference in percentage weigt loss. In TGA termograms different steps responsible for the removal of specific groups from compounds. Eg. water molecules removed at first step near abuot 100 C.

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Art  Follow

Thanks

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Andi Quercia  Follow

Increase height of DTG means the rate of degradation is increasing., In your graphs after radiation the rate is decreased and due to removal of degradation of first peak around 260 to 270 degrees (hemicellulose), after radiation this becomes short, it means hemicellulose is decreased after radiation. Moreove the cellulose peak is shifted slightly to lower temperature but its rate of degradation is decreased too much which ultimately shows improve thermal stability after radiation.
Thanks

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Larry Rafey  Follow

Fatima .... You must first know the molecular weight of the compound you are studying. The next step is to calculate the weight loss in terms of the molecular weight units. If the instruments expresses the results as (%) you can simply multiply the M.W.of the compounds by the % loss. The result will give you the M.W. of the lost material. Example: we were analyzing a heterocyclic compound with a ring containing 3 nitrogen atoms. The calculation gave 28 in M.W. units. The lost portion was simply (N2). We we analyzed the other derivatives and the results were indicative of the lost nitrogen molecule from one molecule of the compound.... If you need further discussion I am available to support youYou may refer to:
Thermochimica Acta, 177 (1991) 329.Thermoanalytical investigations of hetero-cyclic organic compounds. Part 5: thermal decomposition of some substituted n-phenyl-phthalamic acids.Thermochim. Acta, 138 (1989) 13.
Thermoanalytical investigations on hetero-cyclic organic compounds: part 4: thermal decomposition of 1-benzyl, 2, 3-triazoloino-4, 5-n-phenyl-dicarboxiimides.Thermochim. Acta, 79 (1984) 139.
Thermoanalytical investigations on heterocyclic organic compounds: part II: thermal decomposition of substituted 1,4-dihydro,2,4-dioxo-2h3,1-benzoxazine.Thermochim. Acta, 70 (1983) 347-358.

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David W Gault  Follow

I guess she uploaded two curves and asked for the help based on it. Again, be aware that she has asked for the interpretation of TGA plots. I don't see if she has asked for others methods to determine thermal stability. Help and answer on the topic if you can:) Material science deals with n number of testing and characterization techniques and not everyone has access to everything. He/she has to find solution from what is available to them. Moreover, if you doubt on the already established techniques, trying improving your knowledge rather finding faults in technology. Good luck:)

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Abid Hussain  Follow
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Carol Campbell  Follow

Dear, firstly you read out some basic term such as TG, DTA, DTG, DSC and some initial , final , half decomposition temperature, peak temperature. Then after, you must read out thermal decomposition, thermal degradation, mass loss, weight loss, thermodynamic triplet etc

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