Thermal degradation of urea-formaldehyde cellulose composites filled with aluminum particles: Kinetic approach to mechanisms

Abstract

This article reports a study on structural characterization and thermal degradation kinetics of insulating/conducting urea-formaldehyde cellulose (UFC) composites filled with aluminum particles. Structural characterization of UFC/Al composites carried out by SEM, XRD, and FTIR analyses reveals that composites are fairly homogenous, and the interactions between UFC and aluminum in UFC/Al composites are more probably physical in nature. Measurements of inherent thermal stabilities, probing reaction complexity, and thermal degradation kinetics of UFC and UFC/Al composites have been undertaken by thermogravimetric (TG)/differential thermogravimetric (DTG) analyses under nonisothermal conditions. The integral procedure decompositions temperature (IPDT) elucidates significant thermal stability of UFC, and higher aluminum contents in composites are capable of enhancing the thermal stability of UFC resin. TG/DTG analyses suggest highly complicated thermal degradation profiles of UFC and UFC/Al composites, which consist of various parallel/consecutive reactions. Generalized linear integral isoconversional method has been employed to determine the activation energies of thermal degradation processes. Substantial variations in activation energies of UFC and UFC/Al composites with the advancement of reaction verify their multi-step reaction pathways. Advanced reaction model determination methodology with the help of a novel kinetic function F(α,T) reveals that the multi-step thermal degradation of UFC goes to completion by principally following intricate nucleation/growth mechanisms. It is also found that aluminum more likely participates in the thermal degradation of resin and tends to alter its reaction mechanism. Detailed interpretations of the obtained kinetic parameters are given, and their probable physical significances are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44826.