Can nanoparticles really enhance thermal stability of polymers? Part I: An overview on thermal decomposition of addition polymers

Polymer nanocomposites are an important class of polymers that have wide application in a number of different industrial sectors and thus organic/inorganic nanocomposite materials have been extensively studied in the last few decades. Inorganic nanoscale fillers, which are considered to be very important, include layered silicates (such as montmorillonite), nanotubes (mainly carbon nanotubes, CNTs), fullerenes, SiO2, metal oxides (e.g., TiO2, Fe2O3, Al2O3), nanoparticles of metals (e.g., Au, Ag), polyhedral oligomeric silsesquioxane (POSS), semiconductors (e.g., PbS, CdS), carbon black, nanodiamonds, etc. Among the effects of different nanoparticles on polymer properties, many research works evaluate the effect of nanoparticles on polymer thermal stability and fewer papers are dealing with the decomposition mechanism. Thermal stability is mainly studied using TGA, TGA-MS, TGA-FTIR and other techniques. This review highlights the major findings of the effect of different nanoparticles in polymer thermal stability. The whole range of addition polymer matrices is covered, i.e., thermoplastics, thermosets and elastomers. Thermal decomposition kinetics is also a part of this review. The thermal degradation mechanism of these nanocomposites is generally considered to be related to the kind of used nanoparticles and its amount, the structure of the char formed during polymer degradation, the gas impermeability of inorganic nanoparticles, which inhibit the formation and escape of volatile byproducts during degradation and the interactions between inorganic nanoparticles and polymer reactive groups.