Help Help Urgent!! Methods used for data anaylsis of Thermal Analysis

Hello
I am a student studying Polymeric Materials doing Thermal Analysis.
The material for the research is PP/Clay Composites.
The problem I found in my reserach is that the activation energy of that materials is not stable and I cannot find the activation energy by using TGA.
More over I could not find Tg of that material by using DSC.
Could anybody say something about that?
Regards
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Hallo....
snipped-for-privacy@gmail.com schrieb:

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snipped-for-privacy@gmail.com schrieb:

Hallo...
related to your question a short question from my side....what clay do you use ? Do you use an organoclay (modified montmorillonite) ?
Guenter Beyer http://gbeyer.tripod.com
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I use nano silicate clay!
I really need some help.
Regards..
Dr. Hans-Guenter Beyer wrote:

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snipped-for-privacy@gmail.com wrote:

Activation energy? What activation energy are you looking for, and how are looking for it with a TGA? Activation is the temperature sensitivity of a reaction or similar phenomenon to temperature. Polymerization rates, degradation rates, and even viscosity (i.e., momemtum transfer rates) can have an activation energy. What reaction rate are looking for here? Are you looking at mass loss at a series of fixed temperatures? If the activation energy is not "stable", then your reaction is not stable. I would interpret this as that there are multiple reactions in play, each with their own Ea and k, each dominating the degradation at varying temperatures. To sweep the details under the rug and try and derive a "super-activation energy" is too much for the system to handle.
DSC is not the greatest method for Tg detection, especially in blends, as the other materials tend to reduce the signal, and the signal is not all that great to start with. Find another method such as modulated DSC, DMA, dilatometry, ...
John Aspen Research, - www.aspenresearch.com "Turning Questions into Answers"
Opinions expressed herein are my own and may not represent those of my employer.
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You ought to try DMA for Tg.
snipped-for-privacy@gmail.com wrote:

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snipped-for-privacy@gmail.com schrieb:

The reason behind my question was that it is well known that the organoclays will be degraded around 200C according to a Hofmann-elimination reaction....
If you measure within this region an activation energy (maybe for PP degradation) you will have a multiple reaction....so it is important to have a well defined single reaction you are looking for.....
If you explain more in detail we can help you more accurat...
Guenter Beyer
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Sorry for my ignorance in explanations of what I really am doing.
I am looking for the activation energy of degradation of the PP/Clay composites (I am not very sure of the type of clay used in this composite and I do not know the material code yet because the material was passed from another department of my university. I am actually working on the characterization of this material. This composite comes from some research centres to material department and my supervisor gave four types of PP/clay clay composite samples to me to find the thermal and mechanical property . I have tested with TGA, DSC, and DMA. The required results are thermal stability, percent crystallinity, Tm, Tg, Tc, E' and E'' of the samples in different compositions of clay and the improvement of composites compared to pure PP. I have found the method of degration kinetics by Ozawa. I do not know much about this method and so I cannot work with it. Can you say something about Ozawa method for me to have a correct analysis. I can find Tg by using DMA but in DSC scans, I do not find the transition significantly.
Does anyone would like to say something about this?
According to my knowledge the DSC has less sensitivity than DMA.
But I would like to know something with this phanomenon form the point of view of material science.
Dr. Hans-Guenter Beyer wrote:

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Not sure you know about this "A Kinetic Study on the Thermal Degradation of Polypropylene/Attapulgite Nanocomposites" by DTG, comparing thermal stability of PP/clay nanocomposites to pure PP at -> http://taylorandfrancis.metapress.com /(kfhxov2w1yplh2455btai4bi)/app/home/contribution.asp?referrer=parent&backto=issue,1,11;journal,5,34;linkingpublicationresults,1:104477,1
Regarding OZAWA's method I suggest you read this -> http://www.sump4.com/publications/book001.pdf#search=%22Ozawa%20degradation%20kinetics%22 and that you get your hands on a copy of reference 35 in this report for more details ....
Concerning your issue about Tg by DSC versus DMA you ought to know, that DSC measures change in specific heat and DMA measures change in modulus. Highly semi-crystalline polymers, like PP, have only a relatively small amorphous portion and for (highly ?) clay filled PP this total amorphous portion gets even smaller, which is why the absolute change in specific heat is pretty small and therefore very difficult to pick up by DSC. On the other hand is the change in modulus at Tg significant, from highly crystalline to amorphous, which is why DMA shows a very large transition! That's why DMA is one of the best methods for measuring Tg!
snipped-for-privacy@gmail.com wrote:

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snipped-for-privacy@gmail.com wrote:

October 7,06 Boy so much confusion on such a simple solution. So, much has been forgotten in this industry in just 10 short years with downsizing and lay offs in the plastic industry. I guess we are downsizing on intelligence too.
First when someone states that clay degrades at 220C by a Hoffman elimination reaction they are clearly misinformed. This is a filler and has thermal stability in excess of 700C! Its the organic treatment of these nanoclays that degrade via Hoffman elimination as being speculated on by those in the field. The trend incidentally is the use of new ionic fluids.
The degradation rates of the filled PP resin will depend entirely on concentration of the clay and the bulk carrier in this case PP. Depending on the stabilization system used in the carrier resin the kinetic rates at a set temperature will alter in the presence of the filler. Thermal analysis is probably the worse method to use to measure true kinetic rates of PP degradation and to date there has been a poor coorelation between thermal analysis and ASTM Oven stabilty which is the best and most practical mode used today for this measurement. Before you draw conclusions on using thermal analysis you need to explore the literature more. Does not sound like you have done the proper literature search on degradation mechanisms. Suggest you go back to the Polymer Degradation and Stabilization Journals before you even begin to start using thermal analytical equipment to draw these conclusions. Bulk vs 5-10 mg samples with PP vary dramatically and are not even realistic in the real word. In my 37 years in the field of Stabilization I have never been impressed by any reported data on Activation energy as a viable means to predict anything worth mentioning especially when we have seen over 12 changes in catalyst technology and and a continue defortification of stabilization systems world wide.
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Are you sure that contributions in "sci.polymers" represent a complete picture of todays intelligence in the polymer industry ? I don't think so .... !
magicjoe wrote:

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Sorry, You are not right.... The organoclay is a modified clay that contains as an example a quaternary ammonium compound within its galleries. And therefor the organoclays degrade and generate (ideally) the non-modified clay and the Hofmann-reaction products...the resulting clay then is stable indeed
Now I want to go on in the more scentific discussion & maybe the following papers helps snipped-for-privacy@gmail.com ,who wrote :

From the journal "Polymer Degradation and Stabilization" the following 3 publication used TGA to determine activation energies of nanocomposites by Ozawa and others:
=> The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties
Polymer Degradation and Stability, Volume 91, Issue 10, October 2006,
Pages 2443-2450
Guo-An Wang, Cheng-Chien Wang and Chuh-Yung Chen
=> Viscoelastic properties and thermal degradation kinetics of silica/PMMA nanocomposites
Polymer Degradation and Stability, Volume 84, Issue 3, June 2004,
Pages 545-553
Yu-Hsiang Hu, Chuh-Yung Chen and Cheng-Chien Wang
=> Thermal degradation behavior of polyamide 6/clay nanocomposites •
Polymer Degradation and Stability, Volume 81, Issue 1, 2003,
Pages 47-56
K. P. Pramoda, Tianxi Liu, Zhehui Liu, Chaobin He and Hung-Jue Sue
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Sorry, You are not right.... The organoclay is a modified clay that contains as an example a quaternary ammonium compound within its galleries. And therefor the organoclays degrade and generate (ideally) the non-modified clay and the Hofmann-reaction products...the resulting clay then is stable indeed
Now I want to go on in the more scentific discussion & maybe the following papers helps snipped-for-privacy@gmail.com ,who wrote :

From the journal "Polymer Degradation and Stabilization" the following 3 publication used TGA to determine activation energies of nanocomposites by Ozawa and others:
=> The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties
Polymer Degradation and Stability, Volume 91, Issue 10, October 2006,
Pages 2443-2450
Guo-An Wang, Cheng-Chien Wang and Chuh-Yung Chen
=> Viscoelastic properties and thermal degradation kinetics of silica/PMMA nanocomposites
Polymer Degradation and Stability, Volume 84, Issue 3, June 2004,
Pages 545-553
Yu-Hsiang Hu, Chuh-Yung Chen and Cheng-Chien Wang
=> Thermal degradation behavior of polyamide 6/clay nanocomposites •
Polymer Degradation and Stability, Volume 81, Issue 1, 2003,
Pages 47-56
K. P. Pramoda, Tianxi Liu, Zhehui Liu, Chaobin He and Hung-Jue Sue
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Sorry, You are not right.... The organoclay is a modified clay that contains as an example a quaternary ammonium compound within its galleries. And therefor the organoclays degrade and generate (ideally) the non-modified clay and the Hofmann-reaction products...the resulting clay then is stable indeed
Now I want to go on in the more scentific discussion & maybe the following papers helps snipped-for-privacy@gmail.com ,who wrote :

From the journal "Polymer Degradation and Stabilization" the following 3 publication used TGA to determine activation energies of nanocomposites by Ozawa and others:
=> The disorderly exfoliated LDHs/PMMA nanocomposites synthesized by in situ bulk polymerization: The effects of LDH-U on thermal and mechanical properties
Polymer Degradation and Stability, Volume 91, Issue 10, October 2006,
Pages 2443-2450
Guo-An Wang, Cheng-Chien Wang and Chuh-Yung Chen
=> Viscoelastic properties and thermal degradation kinetics of silica/PMMA nanocomposites
Polymer Degradation and Stability, Volume 84, Issue 3, June 2004,
Pages 545-553
Yu-Hsiang Hu, Chuh-Yung Chen and Cheng-Chien Wang
=> Thermal degradation behavior of polyamide 6/clay nanocomposites •
Polymer Degradation and Stability, Volume 81, Issue 1, 2003,
Pages 47-56
K. P. Pramoda, Tianxi Liu, Zhehui Liu, Chaobin He and Hung-Jue Sue
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