Thermodynamic and model-based kinetic analysis of natural rubber–silanised cellulose composites pyrolysis

Natural rubber (NR) composites filled with graded amount of silanised cellulose (CELS) were prepared by melting and vulcanisation. Thermogravimetric (TG) curves at six heating rates (2 to 20°C/min) were measured. Kinetic parameters were determined by using the Friedman model-free method and model-based methods. The following were studied: i) the effect of cellulose silanization on the thermal stability of the composites, ii) the mechanism of pyrolytic decomposition of the composites, and iii) the effect of the content of silanized cellulose on the decomposition mechanism. It was found that the pyrolysis process follows an autocatalytic mechanism. The results also show that silanisation of cellulose has a positive effect on thermal stability, but only up to a certain content of filler.An innovative method for determining the formal thermodynamic parameters was presented, based on the Eyring equation and knowledge of E _α = f (α) and A _α = f (α) from the model-free method; it makes it possible to obtain the thermodynamic parameters as a function of the entire conversion range. Another innovative approach, based on the results from multi-step kinetic analysis, makes it possible to determine thermodynamic parameters for individual steps of a multi-step model and thus to compare the energy demand, spontaneity, and change in disorder of the system in the transition state for individual steps.