Flame retardancy of silicone-based materials

Abstract

This review describes some recent works related to the development of the flame retardation of silicone elastomers and/or applications of silicones as flame retardant agents in other polymers. First, the thermal degradation of silicones themselves is discussed, focussing on depolymerization mechanisms, effect of structure, heating conditions, and effect of additives (i.e. less than 5 wt% fillers) on thermal degradation of silicones. Then, the influence of several types of mineral fillers (of up to 80 wt% content) as ceramization agents of silicones is presented. Finally, the introduction of (functionalized) silicones as flame retardants into other polymers is described.

Effect of cenospheric fillers on the flammability and fire hazard of silicone rubber composites

“…The properties of active filler considerably depend on factors such as shape, size, its distribution in the polymer matrix and the number and quality of functional groups on its surface. For example, laminar or fibrous fillers, contrary to nanofillers, can undergo orientation in processing, while the functional groups on their surface can interact with a polymeric chain, which results in an increase in the composite mechanical properties [8,19].…”

“…Mutual interaction between the particles of active fillers and immobilization of polysiloxane macromolecules on their surface cause the formation of a strongly developed threedimensional filler network that penetrating the whole polymer volume, considerably improves its thermal and mechanical properties [8,9].…”

In situ polymerized wood polymer composite: effect of additives and nanoclay on the thermal, mechanical properties

“…This char layer formed an insulative layer to slow down heat transfer and retarded movement of gases to feed the flame 34 . The reduction in flammability in polymer layered silicate nano materials was due to the pyrolysis of the polymer and a collapse of the nanocomposite structure to form a silicate-carbon barrier that provided thermal protection to the underlying virgin polymer and as a result slowed the rate of volatilization of fuel 13 . The enhancement in properties might be due to the synergistic effect between clay and VTCS during combustion of wood.…”

“…The addition of a relatively low amount of silicon-based compounds (silicones, silicas, organosilanes, silsequioxanes and silicates) to polymers has been reported to substantially improve their flame retardancy 13 . Silane monomers are generally preferred over polysiloxane compounds for impregnation of wood.…”

Effect of mineral filler additives on flammability, processing and use of silicone-based ceramifiable composites

“…The mechanisms of their ceramification, especially the involvement of various types of fillers, have been described in the literature on the subject by Hamdani-Devarennes et al who compared calcium and aluminum-based fillers as main-refractory fillers for ceramifiable composites. They discovered that calcium-based fillers could provide stronger ceramic structure under heat treatment than aluminum-based fillers [5][6][7] and provided a state-of-the-art summary on the subject of ceramifiable composites [8]. Mansouri et al [9][10][11] and Hanu et al [12][13][14] also conducted outstanding research concerning ceramifying silicone composites.…”