An innovative reaction model determination methodology in solid state kinetics based on variable activation energy

•A new reaction model(s) determination methodology has been proposed.•This methodology follows variable activation energy concept.•It may not only kinetically model single step but also multi-step reactions.•It is effectively applicable in isothermal as well as non-isothermal kinetics.•This methodology will provide basis for a number of new reaction models.

Determination of appropriate reaction model(s) in solid state reactions has been confronting with serious discrepancies over the decades. The dilemma in the choice of reaction models originates from the use of facile methods to handle the complicated multi-step kinetics. In order to minimize these discrepancies, an advanced reaction model determination methodology is put forward which deals with variable energy of activation concept. This methodology is expected to fairly simulate single step as well as multi-step reaction kinetics. The fresh expressions for the well known reaction models under this methodology are derived and their validity conditions are discussed. The methods for determining pre-exponential factor(s) in single step and multi-step processes are also reviewed. The proposed methodology is experimentally verified by taking an experimental example of non-isothermal curing kinetics of the polyepoxy formation (by the reaction between DGEBA and an aliphatic diamine) under constant as well as variable energies of activation. The obtained results are compared and effectively interpreted. The precautions while using the said methodology and its prospective applications are also discussed.

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