TGA - Science topic

It seems to me that the key is in the details of the size reduction process . I assume you dry-grind the calcite; if so, maybe you generate an amorphous portion of the sample, which should decompose at a lower temperature than the larger grains. I don't know why the discontinuity between the peaks though; usually grinding will not cause a discontinuity in particle size, but it can't be ruled out. You may be able to check that with a particle size analyzer.

Dear Sevda, have you tried running without any sample? By doing this you can eliminate if this is a true sample transition or an instrument induced signal.

Alundum crucibles have an limit of usability. After several experiments (with appropriate cleaning), it is better to throw them out (including to improve the quality of subsequent experiments). This is a consumable item. And the glass is removed mechanically. Sometimes annealing works (800-1000) with backfilling with calcium or magnesium oxide (but not with alkali metal oxides). Backfill simply "absorbs" the glass, staying fragile.

Did you run the TGA in a nitrogen atmosphere or in the air? It is most likely residual char that will not burn in nitrogen, but it would on air. Also, make sure that you hold the final temperature long enough.

It depends on the sample. At 400 °C, you remove not just the water and other volatiles, but you already decompose many organic compounds such as polymers, oil contamination adsorbed from the air, and skin grease (if you touch the sample with bare hands), etc. These factors will affect the accuracy of your measurement.

Thank you Ali A. Al-Allaq . I will consider your suggestion seriously, as it will clarify any uncertainty.

Usual result of TGA experiment is loss of sample weight due to drying, removal of volatiles, decomposition accompanied with formation and removal of volatile or gaseous components etc. TGA curves, showing weight of the sample as a function of temperature, in these cases present weight reduction. DTG curves (first derivative of the weight over the temperature) show rate of the weight losses as a function of temperature. That is, if no weight loss takes place - DTG is close to zero; if TGA detects weight losses - DTG starts deviate from zero in positive direction indicating non-zero rate of the weight loss. If during the test TGA curve detects weight gains (due to oxidation, for example), DTG curve will deviate from zero in negative direction, indicating “negative” rate of weight losses - weight gain.

Dear Anik Mazumder, if it is to totally eliminate humidity, you can use a trap filled with H2SO4 followed with a column filled with CaCl2, between the gas supply source and the TGA device. My Regards

I fully agree with Dr Philippe Tailhades, as the analisis of TGa curves are based on the loss weight percentage do you need to build the TGA curves in weight percentage to be able to compare

Yes almost certainly an experimental error. However, I would bet on the weighing procedure as the more likely problem. Specifically, since most ionic liquids are hygroscopic, I suspect some weight - in the form of condensed water - was added accidentally after the sample was weighed.

Dear Muneeb

... "however, my concern was if my comparison is valid given that the starting weights/initial weights of the three samples I analyzed were varying from one another".

Since the results obtained are satisfactory when compared with the data of the pure polymer found in the literature, I do not think it is necessary to carry out another measurements. You can (as commonly) show the TGA curves in percentage of weight.

thank you

Naim Aslan and Mohd Faheem Khan

If you had indicated how the sample was obtained, it would have been easier to answer. It would also be nice to make sure (prove) that silicon is present there)). Of course, it would be nice to analyze the initial and final samples (after TG). Most likely it is water (remember silica gel, it adsorbs a lot of water), or the decomposition of residual organic matter.

Haram Fatima

You wrote

1. "N₂ gives a barrier or protection against oxidation more efficiently". More efficiently than what? What is an inert gases?

2. The thermal conductivity coefficients of helium is almost an order of magnitude larger than argon (or nitrogen), but I have never heard of helium being used as a purge gas. Still, the price matters, for helium it is much higher. By the way, inert or inactive gases are also distinguished by the content of oxygen ...

Dear Nur FARADILA Anuar ,

in general the degassing protocol that I suggested should work for PKS biochar. When we refer to biochar we need to consider IBI's and EBC's definition of biochar (e.g. https://www.european-biochar.org/media/doc/2/version_en_10_1.pdf). In p. 20 of the EBC document it is stated that the molar H/C_org ratio must be < 0.7. This is related to the stability of the biochar and is typically achieved at temperatures above 300degC ( ; Figure 4). If you torrified PKS (e.g. 220-300degC) at ambient pressure it may be possible that you alter PKS by degassing it at 180degC under vacuum.

Another aspect to consider is the type of gas to use for BET surface area determination. Historically most people used N2 but there may problems as reported by Christian Wurzer ( ).

Hope this helps?

Dear Dr.Mangrola,

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The following link is also very useful: https://www.spectroscopyonline.com/view/tga-variable-rate-tga-software

Andrew Strzelecki I did not mention this, but the data I have is the mass loss (in %). So probably the main question is whether this is percentage related to the entered mass (270.023), or should it somehow be connected to 20.681 as well. Otherwise, how are those compared to the reference crucible mass?

Chimdi Catherine 105⁰C does not produce much of a thermal gradient in high solid content slurries such as you describe. Time is money and I'd look at reducing the time by increasing the final temperature. Personally I'd look at 119⁰C, 120⁰C, 150₀C and perhaps, 200⁰C to look at result comparability.

I don't fully understand your doubts. The TGA curve looks quite good. But it would make sense to look at TG, since drying is primarily mass loss, and the thermal effect is indirect effect. Also, the heating rate does not inspire absolute confidence. It is quite possible that significant overheating taken place (especially on such a large mass of the sample). Therefore, it is worth looking at the dependence of temperature on time.

Dear Osman Uygun ,

there are three aspects, which have to be considered:

a)Ppenetration depth of your 'surface modification with iron' in your sample;

it might be surface near in the range of a few µm; but I do not know, what you have really done.

b) Penetration depth/information of XRF analysis;

this is in the range of a few 10µm; thus covering the depth of your surface modification, but covers not the whole sample thickness.

c) Information depth of TGA; I think, this is equal to the complete thickness of your sample, which I suppose to be in the mm range. So with TGA you will get a result averaged over the whole sample. Any modification of the sample close to the surface will not significantly affect the averaged result.

I recommend using aThink software

Dear all, please have a look at the following document, hope it will be usefull. My Regards

We have run samples as small as 30 mg and as large as 200 mg in our TGA (the latter using a large volume ceramic pan). An additional advantage of running the TGA as opposed to furnace-based LOI is that you can assess carbonation of your sample from the detailed mass loss vs. temperature plot that is obtained.

Samples acquires moisture relatively very quick. So even it you heat it in an oven and place it in an airtight bag, it get its bound moisture within a short span of time.

We generally keep the sample in TGA at around 50 - 70 deg. for 15 to 20 min for the weight to stabilize. Then we can start the ramp up of heat for the thermal analysis. If your polymer is thermally stable till around 100 deg., then you can keep the sample in TGA at around 80 to 90 deg. instead of 50 - 70 deg.

You´re welcome Sai!

Here, it is better that you run TGA test under inert gas atomoshere ( Nitrogen or Argon purging) for prevention of unwanted oxidation.

Also, for more information, you can search for standard operating procedure of TGA.

Dear Ümran Aşçı, it is very expected that a strong influence of electrospinning process parameters strongly influence the thermal features of fibers. This is because different morphologies/microstructures are built up. Variation in Tm, Tg, degradation threshold temp., and swellability, all varies accordingly. Please have a look at the attached sample document. My Regards

Thanks. The generality of this equation for other polymers need to be tested. Perhaps more detailed study can be made with some representative systems

Dear Hari

Thermogravimetric analysis TGA/DTG, DSC are good for studding the decomposition profile of a sample based on the interpretation of peaks related to mass loss. Based on experience using these techniques but on the kind of compounds you are testing, it is pretty possible to use these techniques for qualitative analysis, but they are not good for that.

Biomass composition could be identified by peaks in the thermal profile but only comparing them with reports. To design a good qualitative identification of biomass components, a better approach is to couple the thermal technique you are applying to Mass Spectrometry which is very strong for accurate identifying chemical molecules in your sample. Then, after your thermal tests, the mass loss corresponding to the losing of moisture, volatiles and rest of components in biomass can be identified by MS. Separation of components previous to MS (such as chromatography) won’t be necessary since the thermal treatment act as a compound separator also (see you own thermal data). Nevertheless, keep in mind that the biomass main components (cellulose, hemicellulose and lignin) are very complex bio polymers, and cause of that, the identification of them by MS won’t be an easy task.

Best Regards

Dear Anjali,

As Florian mentioned, it is not easy to state an adequate answer based on limited data. Please can post a chemical structure?

I agree with Matheus, concerning specificity there are only 2 posisbilities: IR or NMR; XRD does not provide any molecular specificity at all. But you might get the periodicity, if (and only if) a somehow periodic structure will be formed.

(1) You might start with IR/NMR measurements using a series of different L:M ratios starting from 0. Then, you can assign which peak belongs to imidazole, which to imine, and which to the rest.

(2) If you increase the L:M ratio, new (IR) peaks will appear due to binding. Most like they will arise at a lower frequencies/wavenumbers than the corresponding peaks from the unbound moieties. However, there might be exceptions. In most cases stretching vibrations undergo a redshift due to binding, whereas deformation vibrations undergo a blue shift.

(3) After you have the peak assignment you can study the ratio of the peak areas in dependence of the L:M ratio. I expect that particular sturture of coordination strongly depends on the L:M ratio.

I compiled some examples of IR measurements focused binding.

(1)

(2) https://pubs.rsc.org/en/content/articlehtml/2020/sm/d0sm00337a

(3)

(4) https://pubs.rsc.org/en/content/articlelanding/2017/CP/C6CP07215A#cit44

(5)

It might be that not all publications are exactly dealing with imidazole or imine, but you will definitely find instructions and band assingments. Look also in the reference there. Remember temperature changes affect the binding equilibrium somewhat comparable than changing the L:M ratio.

Best regards

I may be biased, but I would save my money for a (not-small) NMR!

Dear all, what is the counter ion of the quaternized polymer ? Possibly, it is not excluded even at high temperature. Thus it counts for residual mass increase. My Regards

Dear Oussama Oulhakem ,

Unfortunately, organics are going to decompose, in several or just at once. There is a high possibility to mistake data, just by TGA output.

Several Russian researchers use DSC to explore heat flux based on metal oxidation. Therefore, an idea of coordination is possible to be achieved, not a full stoichiometry.

Let say you have Fe2+ in the tetrahedral environment with 4 oxygen atoms surrounding it. You may compare the necessary energy to oxidize it with the same Fe2+ atom surrounded by 6 oxygen in an octahedral site. By DSC, you can measure the difference in energy, necessary to oxide them. Therefore, it is possible to distinguish by integration how many Fe2+ atoms are in each different ambient.

Nevertheless, it is a specific problem, demanding the same oxidizing species in both different crystallographic ambient.

You need, as already described by Matheus Mendes and Santosh K Tiwari a DSC coupled experiment, FTIR, Mass spectroscopy, UV, the so-called hyphenated thermal analysis to be able to achieve some reliable result.

Best regards,

WNM

Respected Santosh K Tiwari ,

I have personally asked many such institute/University/Centre having such facilities to do TGA/DSC for starch film or biodiesel. And almost all such institute have rejected to do TGA/DSC for starch film or biodiesel stating that their equipment will get damaged.

But many research papers have reported TGA/DSC analysis for starch film or biodiesel.

Respected Santosh K Tiwari I assure you that I am not lazy nor I am spamming the platform, its only that I have wasted many months searching for institute that are ready to perform TGA/DSC analysis for starch film or biodiesel.

Yes it is possible, but you shouldn't do that.

The kinetic data from single heating run is inherently incorrect, there is a lot of literature on that. In two words, with the limited amount of data you are not able to distinguish between various kinetic models, and the compensation between kinetic parameters is extremely high. For correct procedure of the kinetic analysis consult the ICTAC recommendations (e.g., ). In short, more than 3 heating rates is needed and some advanced kinetic methods. The recommended kinetic methods are available also in free kinetic software developed by myself - thinks.chemphys.ru

Dear Unniyarcha K.K

To determine the thermal stability, measure the change in % mass reduction at respective required temperatures (30 to 800 deg C). When you find a steep mass drop, confirm that your material is not suitable beyond that temperature. This might help your doubt.

Thanks

Glass wool or any other mineral wool cannot gain weight when calcined in air. However, there is a component in your catalyst - nickel, which oxidizes in air and adds weight.

Thank you for your answer

Hello Hari, Thank you for your question.

Elemental analysis used to be done by burning the sample and absorbing the gases of combustion in different solutions, which were then weighed. Modern elemental analyzers accomplish the same task with much smaller sample amounts. Unfortunately, you will not be successful with TGA for this question, since C, H, N and S would have to be released one after the other when heating the sample. In addition, you would have to know exactly in which form the compounds are released.

I wish you much success for your research.

Also check https://harvest.usask.ca/bitstream/handle/10388/12568/GOLAKIYA-THESIS-2020.pdf?sequence=1&isAllowed=y

Dear Rozita

Without knowing what NPs and kind of drug you are using it is not easy to answer your question. I guess that the loaded drug may have a kind of interaction with the NPS that stabilizes these NPs.

Apart from IISc bangalore, Institute of chemical technology(ICT) Mumbai and National Chemical Laboratory (NCL) Pune also have the specified facility

Solid state and Structural Chemistry Unit, Indian Institute of Science, Bangalore

Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore

I think it's better to study DTA instate of the MS

Nayad Abdallah

Reconcile elemental analysis for all methods. Determine the mass average. Write a formula, such as water or hydrogen peroxide. You have determined 12% hydrogen and 88% oxygen. Write the unknown formula HxOy. Find the ratio x: y and, resulting in an integer ratio

12/1: 88/16 = 12: 5.5 = 2: 1. Hence, you have identified water, not hydrogen peroxide.

Dear dr.

I guess that the answer is not straightforward, first you have to detect the mechanism in each stage of TGA, find the first and second derivatives and try to obtain the product at 210C and do MS (mass Spectroscopy) and IR, i.e. Monitoring the product at different stages, but don't forget removing the water attached to the crystal surface by leaving the product 48hr in a 60C oven

Dear Bao,

there is not a direct relationship between the two parameters.

the Tonset or Tstart temperature refers to the start of thermal decomposition, on the other hand, Ea is a kinetic parameter which determines the energy that the reactants must have to transform into products (the energy barrier to be overcome).

isonconversal kinetic models are often used and recommended by ICTAC for solid thermal decomposition studies .

more information on this topic can bé found in our article "Synthesis of copper oxide nanoparticles and their catalytic effect on the thermal decomposition of ammonium perchlorate (ZAAC).

Regards

Marcin Stec Oh. I thought you know and it is clear from the picture.

This is great and almost simple to do with GraphPad Prism software.

It is a bit late to answer Zille huma Malik . Just for other people looking for an answer. When you have TGA results of different materials and mass and looking for comparing them. Make sure you have a mass loss in percentage then it @should be all good.

Dear Dilli, in the first decomposition step you certainly observe the elimination of all eight methacrylate substituents (I assume that you talk about octasubstituted methacrylate POSS, right?). This could certainly occur through decarboxylation, i.e. elimination of CO₂ and the propenyl substituents of the methacrylates in the form of C₃ fragments. In the temperature range of ca. 500-700 °C the breakdown of the Si₈O₈ cage will occur. Did you check if the remaining mass corresponds to SiO₂?

For a related study which includes TGA / DTG measurements please have a look at the following interesting article:

Unfortunately this paper has not yet been posted as pubic full text on RG, but three of the authors have RG profiles. So there is a good chance that you can request the public full text directly from one of the authors via RG.

I hope this helps answering your question. Good luck with your work and best wishes, Frank Edelmann

My experience shows that purification of aluminum oxide crucibles with acidic solutions quickly renders these unusable (they become brittle after 2-3 treatments and often change in weight during the experiment).

For cleaning I usually filled the crucible tightly with dispersed aluminum oxide, place it on aluminium oxide "pillow" and annealed these at a high temperature (for example 1200 C; heating and cooling are slow - for several hours). During annealing, the overwhelming amount of impurities goes into powder oxide. The crucible does not become completely clean, but it is quite suitable for "rough" experiments. For critical experiments, it is preferable to use a clean crucible.

Dear all, usually a good approach via Ellingham diagram is followed to understand the order of stability of compounds including metal oxide. So simple search leads to how the diagram is constructed and used. My Regards

As Yonatan said, it is quite common to use talc for flame retarded PP. However, you indicated the XRF composition is Al and Si. Since talc contains a large amount of Mg, it is likely not talc. On the other hand, using about 15% char yield, the true density of the inorganic filler needs to be about 3.3-3.4 g/cc, which is possible among many silicate (high end) but very unlikely to be used as a flame retardant additive. An inorganic additive using a physical flame retardation mechanism, such as production of nonflammable gas, absorption of heat, and others, requires at least about 30wt% of additives. One seldom sees only 15wt% additive without chemical mechanisms, such as halogenated or phosphonate. A more likely scenario is that the filler may contain a volatile component, such as carbonate or hydrate, so that during the TGA analysis, those small molecules decompose and evaporate. Thus, despite adding, say 30-40%, the TGA analysis after heating to about 800-900oC leaves only the none-volatile component. This is consistent with the small char yield, but addition of relatively large fraction of inorganic component at the room temperature value.

The first reasons which come to mind why a TG investigation is planned, are:

* to determine the stability and the content of the volatiles in a material;

* to study a material without interference of oxygen;

* to prepare an inert environment into which the active components of interest can be subsequently introduced.

With this diversity of possible applications, one cannot go much further with advice.

However, some precautions are likely to be of use:

* Even the highest vacuum is never free of molecules; actually, there are plenty of them. Achieving a non-oxidizing environment by evacuation is totally impossible due to the residual leaks and outgassing; the water vapor, always present in up to 500 layers of molecules on every practical surface, can oxidize even stronger than oxygen can. That includes the water vapor on the surfaces of the mechanism of the balance of the TG instrument.

Since the ideal vacuum is un-achievable, a more practical choice is admitting that fact, and working with an added residual bleeding of an inert gas trough the balance chamber, then through the area where the sample is. 1 Torr or a fraction of it can be much more stable in every respect than the "10-6" We need to remember that the vacuum gauge is measuring it's own environment, while the vacuum level at the other locations is anyone's guess.

* 1 ml of air weighs about 1000 micrograms, so evacuation of the moving parts of the balance plus the sample and its support produces a strong shift of the zero line. Still, some procedures allow achieving a ppm precision.

* Samples of the materials when thermally decomposing, produce condensable fumes which can destroy the TG instrument almost immediately.

And so on, and on, and on. A thermogravimetric experiment can produce rich information, but it requires a thorough preparation, to be meaningful. This is the area of conflicts between the user and the customer-support department of the instrument's manufacturer. They say: "The instrument seems to be working properly, as designed." - The user: "The instrument itself may work OK, but it does not work with my samples!" - "Sir, you certainly know much more about your materials than we possibly can; we are only responsible for the performance of the instrument." - "But I have paid so much money for the instrument to study my materials!" - "I recommend your checking Google if any other user had your problems." Please note this: "... your problems". No way around, TG researchers have to research how to use their instruments with their materials. They are never as straightforward as a tape measure.

In this respect the term "capibration" sounds to belong to the area of hopes.

If you are more specific about your experiments and measurements, a more focused help can be tried.

Jerry C.

Dear Eman Fahmy, you should specify wether it is an organic or an inorganic filler. The effect of inoganic minerals additives is more or less understandable. For example CaCO3 imparts additional thermal stability to many polymer such as PVC. The effect of fillers type and loading is much more seen if the mechanical properties are evaluated at different degrees of temperature. The changes is the stages of TGA thermograms also may be an indication when compared to the virgin unloaded matrix. My Regards

Dear Amin Niamir,

I have attached one article which described the TGA analysis of Amorphous calcium carbonate (ACC). I hope it would be useful.

You can use my software - thinks.chemphys.ru - to perform thiskind of analysis

Thank you Ali. I am so sorry for not asking the right question. I was in a hurry and wanted to post question before I go on to other project. Actually Epoxy-isocyanate can have multiple reactions going on simultaneously. Depending on the amount of either epoxy or isocyanate, one reaction favors over other. So when I look at FTIR, I see peaks corresponding to oxazolidone, isocyanurate, if reaction is not complete isocyanate, and homo polymerization of epoxy, so I was asked by my researcher how many percent oxazolidone is formed? So question was regarding that. I have received a paper I requested from ResearchGate from Xavier Ramis and it has mentioned how to calculate. I am going to read carefully and try to learn . Thanks again.

I have used FTIR for quantitative analysis using a quant program in the past.

Thank you.

You should also consider decreasing the heat flow rate - increasing the measurement time (22 min for 570ºC)

Please use this link: http://www.thinks.chemphys.ru/shiny/Redir/

A lot of information can be useful.

Best of luck

As a suggestion, I can say that the different components in TGA analysis are eliminated at different temperatures. The mass release for water, Ca(OH)2 and CaCO3 will be different. Particularly, the attention in water should be centered around 100°C. In this case, you will see a peak around this temperature in the derivative of the mass loss. By knowing the amount of the sample used (in grams for example) and knowing the % change of the sample at his particular temperature, you can calculate how much water was released.

Vianney Andrew Yiga TG graph can be presnted as mass plotted against temperature or mass loss plotted agaainst temperature. If you plot mass vs. temperature, it starts from 100%. It, in fact, presents residual mass plotted against temperature. But if you really mean, mass loss, it should start from 0%. Please check my previous answer again carefully.

You are welcome, I am glad to hear that you have solved the problem.

Dear Nikou Hamzehpour,

I have attached two articles which TGA method of soil has been explained. I hope they would be useful.

@ Ana thankyou for your suggestion.

Only an additional chemical reaction can cause this, for example, oxidation. So the experiment should be conducted in a nitrogen atmosphere. However, such a small peak is presumably an instrument error that the software did not compensate for.

You need the initial mass (m) of the sample which used for the TGA. Then:

Percentage release of inhibitor (%) =(M_t.V)/(m.w) × 100 %

where V (mL) is the volume of the release medium and w is the TGA weight loss percentage (here 0.18).

Also, denominator of the formula is the released amount in µg at time t and the numerator is the total amount of the inhibitor inside the container in µg.

Dear Janitha,

There are two events occurring at 330.81 and 515.28 deg C.DGEBA is a symmetrical molecule and has high stability, but also it is an organic bulky molecule, hence the energy required to break DGEBA maybe substantially higher as compared to conventional organic compounds but also lower than inorganic substances. This means at 330.81deg C , there is a weight loss(probably due to cleaving and elimination at the phenylpropan2-yl region ) and the second event at 515.28 deg C because of elimination of the oxiran group.

TGA shows solvate formation-can be determined with 100% certainty subject to the users experiences and skills.

DSC shows extra full endotherm of cocrystal-cannot be as certain as that by TGA.

scxrd shows different cocrystal-different diffraction peaks can and can ONLY conclude a new physical form, which can, however, be a different polymorphic form, salt form, or cocrystal form, if applicable.

It is important to have a representative sample size when conducting TGA analysis of cementitious or other multi-phase materials. At NIST, we generally tried to use our large volume TGA pans and get a sample size close to or exceeding 100 mg.

Also, results often depend on from which temperature you are measuring your final weight loss. In your figure 7, one can observe that already by 100 C, when the sample should be losing mostly free water, samples 5 and 6 have much less mass loss than those of 1-4. Perhaps these samples were allowed to "dry out" more prior to being loaded into the DSC. You can try renormalizing your mass loss results using the 100 C masses of each specimen as the new basis. This should definitely get rid of some of the variability between specimens.

Regarding the heat flow plot, it would be better to plot the y-axis as heat flow per unit mass as otherwise it is difficult to compare the various curves.

From the mass loss curves, the mass loss between 400 C and 500 C is usually attributed to water lost from calcium hydroxide and while it is difficult to tell exactly from viewing the curves, the six specimens appear to have fairly similar absolute mass losses between 400 and 500 C. This would suggest that the free water loss (prior to 100 C) may indeed be biasing the subsequent cumulative mass loss curves and normalizing based on the mass measured at 100 C may be a good way to go.

Good luck,

Dale

Aging under H2O or CO2 will end up with a material behavior below 120 C. To follow the behavior of a polymer, the changes in composition and structure may not exceed 400 C because the material is totally destroyed and only carbon may be left if any. Thus, listing examples occurring above 600 or 900 C is completely beyond the study of polymer decomposition. Regards