Zinc oxide (ZnO) has been demonstrated as a PIN flame retardant in a range of materials, including wood, natural fibres and PVA (poly vinyl alcohol) and nano-sized particles of the mineral have shown better dispersion. In this research paper, daisy-shaped zinc oxide nano-wires, diameter 80-120 nm and length 1.5-3 µm, were tested at loadings of 0 – 40 % in polypropylene. A 30% loading of zinc oxide nano-wires reduced peak heat release rate (PHRR) to below 2/3 of the PHRR of neat polypropylene, decreased total heat release rate, increased degradation onset temperature (+34°C), and reduced maximum smoke density (MSD) to below ½ that of neat polypropylene. These results are similar to those achieved with the same loading of non-nano zinc oxide. The authors note that the nano zinc oxide leads to more rapid char formation.
“Enhanced flame retardancy and smoke suppression of polypropylene by incorporating zinc oxide nanowires”, J. Guo et al., Journal of Polymer Research (2019) 26:19 https://doi.org/10.1007/s10965-018-1680-6