Kinetics of dynamic percolation in polymer/carbon composites

Abstract

Dynamic percolation differs from static percolation in polymer composites owing to its occurrence at a particular filler fraction under thermal activation. Mechanistic insights into dynamic percolation might lead to develop polymer composites with controlled electrical properties at lower filler fractions and improved temperature coefficient of resistance phase transitions. Although attempts have been made to kinetically describe the dynamic percolation in polymer composites, a generalized mechanism-based approach has not yet been reported. In this article, a systematic and generalized theoretical approach to kinetically model the dynamic percolation in polymer/carbon composites has been put forward. Based on the proposed approach, a kinetic expression to predict the quasi-thermodynamic equilibrium state in a polymer/ carbon composite at constant temperature is derived. The soundness of the proposed approach is justified by its effective applications on poly(vinylidene fluoride)/multiwalled carbon nanotube (PVDF/MWNT), poly(vinylidene fluoride)/carboxyl-functionalized MWNT (PVDF/MWNT), high-density polyethylene/carbon black, and poly(methyl methacrylate)/carbon black composites. Certain mechanistic complexities of dynamic percolation are also pointed out and discussed. POLYM. ENG. SCI., 60:423-433, 2020.

Predicting thermal degradation mechanisms in urea–formaldehyde cellulose composites filled with tin particles

“…Furthermore, this behavior is found dependent on tin contents in UFC. The uneven thermal degradation behaviors demonstrated by UFC/Sn composites in comparison with UFC resin may be fairly explained on the basis of competitive variations in catalytic activity and heat capacity of tin as already explained in the previous studies . In this context, the main reason behind the behavior shown by tin in UFC/Sn composites, on one hand, can be its fine catalytic activity at relatively lower temperatures which might diminish at higher temperatures.…”

“…Tin (Sn) is one of prehistoric metals familiar for its relative abundance, nontoxicity, malleability, and ductility, ease of alloy formation by having low melting point and chemical inertness at room temperature, and therefore, fine metal protection ability . Polymer composites containing tin filler establish a fascinating class of materials which is economical, environmentally friendly, and multipurpose . Composites of urea–formaldehyde cellulose (UFC) filled with tin particles belong to the motioned class of materials, and they exhibit numerous valuable and wide‐reaching applications .…”

“…UFC/Sn composites can be categorized into electrically/thermally insulating/conducting composites, though both of them are equally useful. Insulating composites are potentially applicable as thermal greases, thermal interface materials, and electric cable insulations, while conductive composites can be put into thermoelectrical and thermomechanical applications, and organic photovoltaics .…”

“…Authors have put forward an advanced approach to kinetically interpret the thermally stimulated condensed phase processes, and to cope with their complexities . Thermal degradation behaviors of epoxy and insulating and conducting epoxy/Sn composites have already been simulated by the application of the suggested approach, and profound insights into their thermal degradation pathways are obtained . In this research, the same approach will be applied to the thermal degradation of insulating and conducting UFC/Sn composites, and the obtained mechanistic information will be interpreted and discussed.…”

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

“…Nevertheless, the thermally activated condensed phase processes are familiar for their complexities, and even an apparently simple reaction might consist of multiple steps. Authors have put forward an advanced approach to kinetically model the thermally stimulated condensed phase processes and to deal with their complexities . The application of this approach on conducting and nonconducting epoxy/metal composites simulates the thermal degradation behaviors of those composites by presenting interesting mechanistic information .…”