The synergistic effect of functionalized montmorillonite with intumescent flame retardant in EVA

Abstract

An intumescent flame retardant (IFR), a Schiff-base polyphosphate ester (PAB)-functionalized montmorillonite (PAB-MMT) was combined with PAB to adopt into ethylene–vinyl acetate copolymer (EVA) by melting intercalation. The synergistic effect between PAB-MMT and PAB was evaluated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), limiting oxygen index (LOI), vertical burning test (UL-94), microscale combustion colorimeter (MCC) and scanning electron microscopy (SEM). The results showed that when 5.0 wt% PAB-MMT replaced the same amounts of Na-MMT in the composite, the flame retardancy of EVA/PAB composite was improved. For this composite, the LOI value was increased and the ignition time in UL-94 rating was shortened compared to pure EVA or composites containing PAB or Na-MMT/PAB. The MCC results indicated that the peak heat release rate (PHRR) and total heat release (THR) were significantly reduced in comparison with other EVA nanocomposites. Meanwhile, the TGA data showed that the EVA/PAB/PAB-MMT nanocomposite had higher char residue than the EVA/PAB and EVA/PAB/Na-MMT nanocomposites. The TEM and dispersibility measurement results showed that PAB-MMT had better dispersion than Na-MMT. The SEM results demonstrated that the minimal loading levels of PAB-MMT in EVA/PAB/PAB-MMT composite had a well-structured and strong char which had better ability to endure heat erosion. A good synergistic effect between PAB-MMT and PAB was constructed.