Simultaneous thermal analysis of cationic, nonionic and anionic polyacrylamide

Polyacrylamide (PAM) and its derivatives are the most commercially available water-soluble polymers and are frequently used for the production of clay-polymer composites. The characterization of their thermal behavior and decomposition was carried out mainly under reduced conditions by using N₂, He or Ar gas flow. The object of this study was to investigate the thermal decomposition of cationic (PAM_S,τ40Cl), nonionic (PAM°_S), and anionic (NaPAM_S,τ40) polyacrylamide under synthetic air (SynA) in detail using a thermogravimetry/differential scanning calorimetry (TG/DSC) system connected to a quadrupole mass spectrometer (MS). MS data indicated the release of NH₃, CH₄ and NO together with H₂O, CO₂ and NO₂ during decomposition. The gas release differed between the three polymers. Stoichiometric calculations showed that PAM_S,τ40Cl and PAM°_S decomposed completely, while NaPAM_S,τ40 decomposed only partially and the Na present for charge balancing remained in the form of Na₂O. The thermal decomposition of PAM_S,τ40Cl, PAM°_S and NaPAM_S,τ40 under SynA occurred via pyrolysis and oxidation reactions.