Dear Beth Sarsfield,

Many thanks for your help. I will go through this.

Dear Tihomir Nikolaev Tsanov,

Many thanks for your valuable answer.. Definitely it will help full to me.

As you expected I used 20:80 monomer feed ratio for copolymerization. So may be 80% mass loss of epoxide block and 20% mass loss of anhydride block..

or 

It may be the new polymer which has two segment one segment may be stable up to 300 oC another may be stable up to 440 oC.

Thank you!!

Yes. I will go with Tihomir Nikolaev Tsanov answer.

Your co-polymer consists of epoxide  and  anhydride  blocks. So, if you know the initial ratio of the monomers, and mass loss during degradation of the material, you can assume that the epoxy parts are about 80 %.

Check polyepoxide degradation in literature.

Thank you dear Narasimha.

In my opinion you have received good answers to your question.

One more technique you could use if it were available for you: a combination of a TGA with a mass spectrometer. The gases liberated in the decompositions are channelized inside the spectrometer. and later can be identified by molecular masses.

Dear Jose A. R. Cheda,

Thank you for your kind suggestion. 

Anhydride is more stable and it decomposes in the second stage. Epoxy is expected to decompose through weak bonds in the first stage.

In fact in some cases during decomposition anhydride is formed, which decomposes at the end.

Dear Asit Baran Samui,

Many thanks you for your helpful answer. Is there any report during thermal degradation cyclic anhydride generation?? If you have any refer file please send me. Once again thank you for spending your valuable time. 

Dear Sreenath Pappuru

I defer to the others in their expertise of polymer chemistry. 

From a thermal analysis technique perspective: It may be useful, if you have the capability, to use coupled TGA-GC/MS or TGA-IR to shed some more light on the decomposition products - I would anticipate the anhydride and the epoxy to release different decomposition products - which is given off when may help to confirm their hypotheses as to what is happening here. Less ideal, but still potentially useful, may be to capture aliquots of off-gas in an IR gas cell during each step or in a GC/MS gas injection syringe - then you could still get the information, possibly without needing an expensive heated transfer cable. 

Best regards, 

Sarah Ackermann, MSc

Thank you Dear Sarah Ackermann. Definitely I will look in this direction also.