Effect of Organo-Modified Nanosepiolite on Fire Behaviors and Mechanical Performance of Polypropylene Composites

The objective of the study was to investigate the effect of the organo-modified nanosepiolite (ONSep) on improving the fire safety of polypropylene (PP). The composites based on PP, flame retardant master batch (MB-FR, 25 wt% PP+50 wt% decabromodiphenyl ether (DBDPE)+25% antimony trioxide (ATO)) and ONSep were prepared via melt blending. The results of the limiting oxygen index (LOI) and vertical burning rating (UL-94) test indicated that PP/40 wt% MB composites had no rating with seriously dripping phenomenon, while the LOI value was only 22.5. However, as 4 wt% ONSep was added in PP/40 wt% MB composites, the composites achieved UL94 V-0 rating and the LOI value was 24.3. In comparison, PP/50 wt% MB composites could not reach the V-0 rating either. The TGA results revealed that the addition of ONSep enhanced the thermal stability of the PP/MB-FR composites. The cone calorimeter results indicated that the heat release rate, average mass loss rate, smoke production rate and smoke temperature of the PP/40 wt% MB-FR/4 wt% ONSep composites decreased in comparison with those of PP/40 wt% MB-FR composites. Simultaneously, the Young modulus and impact strength were also much better improved with the increase of ONSep loading. Therefore, the synergistic flame retardancy of ONSep in PP/MB-FR matrix significantly containing a halogen based flame retardant (DBDPE) significantly improved the fire safety and mechanical properties of the composites, and allowed to decrease the total amount of brominated fire retardants.