Complex activity of clay and CNT particles in flame retarded EVA copolymer

Interface modifications optimized for fire retardancy require detailed research. Confocal Raman microscopy was used to analyze the degradation locally in the area of the nanotube and clay additives. The double-walled carbon nanotube (DWCNT), containing Co catalyst residue, accelerates the deacetylation process of poly(ethylene-co-vinylacetate) (EVA) considerably, while the montmorillonite (MMT) has no significant influence under static circumstances. The compounding process influences the effect of MMT, which causes partial crosslinking in EVA during the compounding. This mechanochemical reaction is catalyzed by uncovered MMT particles, while organophillized MMT promotes the charring process. Inorganic surface modification with various metal ions has also some stabilizing effect. Spray drying of MMT results in microparticles of increased surface area and improved thermal stability of the EVA system. The lowest rate of flame spreading was achieved using uncoated MMT, while coating with cationic surfactant was most efficient for hindering dripping. The rate of heat release (RHR) of the organically modified and the spray dried MMT was approximately the same. The combined organic-inorganic modified clay moderates both the dripping and the flame spreading in the EVA. Copyright © 2006 John Wiley & Sons, Ltd.