Thermal degradation of carboxymethylcellulose in different salty forms

Carboxymethylcellulose (CMC) salts in different counter-ion forms were obtained and characterized by FTIR, CP-MAS 13C NMR and EDX spectroscopies. Additionally, thermogravimetry (TG) was used to evaluate the degree of humidity and the thermal stability. In general, CMC samples having Li+, Na+ and K+ as counter-ions showed a high hydrophilic character, absorbing more than 50% in weight of water, while for CMC having Mg2+, Ca2+, Ba2+ and others cations the hydrophilic character was lower than the former, absorbing less than 30% of water. All of the CMC salts showed lower thermal stability than their cellulose parent. Typical values of Tm, in °C, and Ea, in kJ mol−1, were for cellulose: Tm = 349.11, Ea = 178.8 ± 8.4; CMCK: Tm = 283.61, Ea = 152.9 ± 1.0 kJ mol−1; CMCCa: Tm = 305.67, Ea = 167.2 ± 5.2 kJ mol−1. Different kinetic models were found for the CMC salts as Šesták–Berggren, reaction order and Johnson–Mehl–Avrami.