Thermal Analysis on the Stabilization Behavior of Ternary Copolymers Based on Acrylonitrile, Methyl Acrylate and Itaconic Acid
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Polyacrylonitrile (PAN)-based copolymers are widely used as a precursor for manufacturing high performance carbon fibers via a series of processes of thermal stabilization, carbonization, and graphitization. We have recently synthesized a series of copolymers with various compositions of acrylonitrile (AN), methyl acrylate (MA) and itaconic acid (IA) by using an efficient aqueous suspension polymerization. In this study, the influences of MA and IA units on thermal stabilization behavior of AN/MA/IA-based terpolymers has been investigated by thermal analyses using DSC and TGA. It was found that the glass transition temperatures (Tg) of AN/MA/IA-based terpolymers with a constant AN content increased with the IA content due to a specific interaction between carboxylic acid and nitrile groups, while the MA unit played a role of lowering Tg of the copolymers owing to the interruption of AN sequence with a strong dipole-dipole interaction. The exothermic peaks of DSC curves as well as the weight loss of TGA/DTG curves under air condition revealed that the IA unit in AN/MA/IA-based terpolymers contributed to accelerate the oxidation reaction especially under air condition and also to slow down the following cyclization and dehydrogenation reactions including isomerization, unlike PAN homopolymer and AN/MA-based bipolymers. On the other hand, the MA unit in AN/MA-based bipolymers and AN/MA/IA-based terpolymers served as a delaying agent on the overall thermal stabilization reactions of oxidation, cyclization and dehydrogenation.
KeywordsPolyacrylonitrile Terpolymers Thermal stabilization Thermal analysis
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