POLY(STYRENE-CO-ACRYLONITRILE) FOAMING WITH SUPERCRITICAL CO_2: INFLUENCE OF NANOCLAY ON THE FOAM MORPHOLOGY AND FLAMMABILITY

摘要

Polymeric foams are attractive materials due to their low weight, high impact resistance, thermal insulation, etc. However, these materials, mainly composed of voids, are highly flammable, which limits their use in several applications, like house decoration. For a few years, lamellar nanoclays are driving an increasing interest due to their ability to modify polymers combustion behaviour with only a few percent of well-dispersed filler while increasing the material strength. In this work, we have used supercritical carbon dioxide (CO_2) as the physical blowing agent in order to prepare poly(styrene-co-acrylonitrile)/clay nanocomposite foams. The influence of the foaming conditions on the cellular structure is first deeply investigated, with a particular emphasis on nanoclay effect on the cell size and cell density. Then, the burning behavior of the nanocomposite foams is characterized with cone calorimetry. The peak of heat release rate (PHRR) is assessed as a function of the nanoclay delamination level and the percentage of nanofiller added. The lamellar nanofiller shows fire retardancy as attested by the significant experimentally observed PHRR drop. In a last step, the clay is combined with a non-halogenated flame retardant, melamine polyphosphate. We observe that the two fillers act in synergy to reduce further the PHRR.