Thermal degradation and flammability behavior of polypropylene/clay/carbon nanotube composite systems

This paper reports on the testing and development of a polypropylene (PP) nanocomposite systems with improved flame retardancy. The work utilizes the unique properties of sepiolite nanoclay (Sep) in combination with carbon nanotubes (CNTs) in order to develop an optimized ternary nanocomposite system. Thermogravimetric analysis (TGA) showed significant improvements to the residual char towards the later stages of the thermal ramp. The pyrolysis combustion flow calorimeter (PCFC) was employed to screen the various PP composites with respect to their potential flammability performance. The heat release capacity, which is an indicator of a materials fire hazard, did not show any reduction with the addition of nanofillers using the apparatus standard testing procedure. However, this changed by switching to a lower burn within the PCFC's furnace; this diverted oxygen to the pyrolysing sample. Using the results gained from TGA and the PCFC, the optimized ternary nanocomposite system (10wt.% Sep+2wt.% CNT) was compounded on a larger scale and tested in the cone calorimeter. This showed a significant reduction of 82% in peak heat release rate in comparison to unfilled PP. Comparisons were also made between the testing of these samples in the PCFC and cone calorimeter. The main objectives were to develop a flame-retardant PP nanocomposite ternary system as well as assessing the PCFC with traditional techniques. Copyright (c) 2012 John Wiley & Sons, Ltd.