Chapter 3 - Polymer nanocomposites from the flame retardancy viewpoint: A comprehensive classification of nanoparticle performance using the flame retardancy index

Abstract

Polymer nanocomposites are heterogeneous systems, mainly composed of one polymer and one or more nanoscale particles, showing a wide range of properties depending on the properties of the parent polymer and nanoparticle, composition, microstructure, and particularly the status quo of interfacial interaction between the polymer matrix and nanoparticle. Flame-retardant (FR) nonhalogenated nanocomposites are solutions to inadequate flame retardancy of polymers, but FR nanocomposites are in early stages of their development period. Although there are plenty of reports on the use of nanoparticles in polymers from different families directed toward the analysis of their flame retardancy performances, there is no comprehensive framework to classify polymer nanocomposites based on the performance of nanoparticles’ flame retardancy performance. The main reason for the relatively slow growth in nanomaterial usage in flame retardancy is the lack of efficiency of nanoscale additives compared with conventional FRs. This is why a great body of research in this field has been devoted to explore the effect of the combined use of nanoparticles and conventional micrometer-sized FRs in polymers. For instance, no complete image has been provided by researchers on the FR efficiency of nanoparticles in polymer matrices. Moreover, there is no universal criterion as a practical measure for flame retardancy of nanoparticles, arising from the personalization and/or predilection of opinions of researchers working in the field with their own preconceptions and partialities. This chapter provides an overview of available data and presents the recent progress in the flame retardancy of polymer nanocomposites with the aim of classification of reports on the basis of the performance of nanoparticles of different families (mineral, metal oxide, silicone-based, and carbon-based nanoparticles) by their qualification (Poor, Good, and Excellent) in terms of a newly introduced measure for flame retardancy performance analysis, known as the flame retardancy index (FRI). FRI is a dimensionless universal index that allows comparison between the levels of flame retardancy performance of nanocomposites based on cone calorimetry data.