Case study 3 Kinetic studies by TGAAhmad N.
et al. (2014) study thermal stability and kinetic parameters of Sodiumcarboxymethyl cellulose and kinetic investigations of polymeric materials by TGAtechniques to analyze the data. The kinetics of the thermal transformation of asolid state chemical reaction is usually described by the general equation. (3)Where ? is a degree of conversion/reacted fraction, t is the time, Tis the process temperature and k(T)is a temperature dependent constant and f(?)is the reaction kinetic model, accounts for the reaction rate dependence on ?.The kinetic model is an algebraic expression, which is frequently associatedwith a physical model that describes the kinetics of the solid state reaction.
k(T) is usually approximated by the Arrhenius equation. (4)Where A, E, R and T are the pre?exponentialfactor, the apparent activation energy, the universal gas constant (R = 8.314 J/mol.
K), and the absolutetemperature, respectively. For a dynamic thermogravimetric process, Equation 1can be modified using the definition of the constant heating rate, ? = dT/dt, as in the equation 5. (5)This is afundamental equation of solid kinetics. One of the few difficulties encounteredin using Equation 3 is the determination of the E of a reaction withouthaving any previous knowledge about the reaction model. There are severalmethodologies to evaluate the thermal degradation kinetics 21.
Ahmad N. et al. (2014) study nonisothermal decompositionbehavior of NaCMC and their masslosses, the onset temperature ofdegradation (Tonset), maximum degradation rate temperature (Tmax),mass loss percentage at Tmax and residue mass loss atdifferent heating rates are evaluated. The results are listed in Table3.