In case of polycaprolactone-based polyurethanes (MDI as diisocyanate and butanediol as chain extender) which segment (soft segment or hard segment) will decompose earlier during the TGA analysis?
It's a soft segment which will decompose earlier than hard segment..
The first stage of degradation is related with the urethane decomposition into isocyanate, alcohol and amine. The 2nd and 3rd stage is related with the dissociation of soft segment. The final stage is related with the dissociation of isocyanate into carbodiimide and carbon dioxide.
Thank you all for giving your valuable time and suggestions. I think it the hard segment which will decompose earlier. Thank you Sonalee for the nice explanation. Progress in Polymer Science 34 (2009) 1068–1133 is an interesting review on thermal stability of PUs.
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