Modification of organo-montmorillonite with disodium H-phosphonate to develop flame retarded polyamide 6 nanocomposites

Montmorillonite (Mt) hold a great potential in improving inflammability of polyamide nanocomposites. This paper presents research on a novel class of flame retardants prepared by adsorption of disodium H-phosphonate (DHP) on the sodium montmorillonite (Mt) and organophilized montmorillonite (OMt) - clay surface. Using instrumental analyses including X-ray diffraction (XRD), thermogravimetric analysis (TGA), cone calorimetry, limiting oxygen index (LOI), UL-94 technique and scanning electron microscopy (SEM) the influence of DHP and Mt or OMt in PA6 on the thermal stability and fire reaction properties of PA6 was investigated. The adsorption of DHP on Mt and OMt delayed the onset of the degradation temperature of PA6 by 8 and 23 °C, respectively. The flame resistance of nanocomposite with 0.75 wt% of DHP stabilizer adsorbed on OMt surface was significantly improved as 59% reduction in maximum peak of heat release rate compared to neat PA6 was observed. The UL-94 and cone calorimeter results have shown that the tested materials burn differently, which are reported here as three behaviors during combustion. Based on these results it was found that the surface-modified Mt protects the polymeric material against the degradation within the temperature range used by formation of phosphorus-mineral char.