Thermally induced degradation of NaCMC in water and effects of NaHCO3 on acid formation and charge

•NaHCO3 buffer retarded degradation of NaCMC especially at high temperature.•The side groups of NaCMC were relatively stable against thermally induced degradation.•In addition to hydrolysis also oxidative reactions likely occur at high temperature.

High purity (>99.5%) NaCMC solution was heated in ion-exchanged water and in an aqueous 10 mM NaHCO3 buffer solution and studied as a function of time and temperature. The effects of thermal treatment on viscosity, pH, molecular weight and cationic demand of the solutions were measured. It was found that the anionic groups of carboxymethylcellulose are relatively stable against thermally induced degradation, but a reduction in NaCMC chain length and viscosity was observed. Only the highest applied temperature (177 °C), especially without any pH control, destroyed the side groups of the NaCMC. This was observed as a decrease in cationic demand and in the formation of glycolic acid. The application of buffer was noticed to retard the degradation of side groups. The observed decrease in viscosity with increasing reaction time in the presence of air was relatively well described by a second order reaction.

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