Effect of Layered Silicate Nanocomposites on Burning Behavior of Conventionally Flame-Retarded Unsaturated Polyesters

Abstract

Montmorillonite clay has been modified with a series of organic modifiers. Modified clays have been characterised by X-ray diffraction and thermal analytical techniques. Unsaturated polyester nanocomposites have been prepared by in-situ polymerisation. Some clays were fully exfoliated, some indicated combined nano-structures with ordered intercalation and partial exfoliation, and some indicated only microcomposite structures, depending upon type of organic modifier used. Thermal stability and flammability of these samples have been studied by thermal analysis and cone calorimetry. All clays reduce the onset of decomposition temperature of the resin, slightly increase ignition time and total burning time but decrease peak heat release rate (PHRR) values (9-36%) and total heat release rate (THR) (2-16%) compared to resin only sample. In the presence of conventional flame retardant, ammonium polyphosphate (APP), there is a synergistic effect with the nanoclay in terms of increased char formation, reduction in PHRR (60-67%), THR (35-39%) and smoke production (1-13%) compared to resin. Mechanical testing in terms of flexural mode has indicated that inclusion of functionalised nanoclays enhances mechanical performance of the resin.