Mode-of-action of self-extinguishing polymer blends containing Organoclays

We showed that a synergy from a combination of modified organoclays with halogen flame retardant (FR) additives can render polymer blends selfextinguishing. Primarily, we investigated the fact that small amount of the clays can produce in a large reduction of heat release rate (HRR) and mass release rate (MLR) in a PS/PMMA polymer blend due to a formation of networks composed of the clay platelets, which form themselves into nanotubes during combustion. In order to confirm this unique behavior of the clays, by use of transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and scanning electron microscopy (SEM), the degree of intercalated and exfoliated clays is confirmed at several high temperatures. In addition, the amount of the Br particles left after combustion was visualized by using an energy dispersive X-ray spectroscopy (EDXS). Furthermore, extended X-ray fine absorption structure (EXFAS) was used in order to verify the possibility of a changed chemical structure of the Br particle in the gas phase. We applied the synergy to other system, PC/SAN24, in confirming the effect on heat releaserate (HRR) and mass loss rate (MLR) by the addition of the clays to the system. Even though the clays were compatibilized in PC/SAN24 polymer blend, the system did show such a large reduction of the HRR and MLR probably due to hindrance by the clays to the chain scissions of PC, which lead to char formation. Therefore, we believe that the synergy is able to occur when only non-cross-linking polymers exist in a system.