Synergistic effect of Nano‐ZnO and intumescent flame retardant on flame retardancy of polypropylene/ethylene‐propylene‐diene monomer composites using elongational flow field

Abstract

In this work, the synergistic effect of Nano‐ZnO and intumescent flame retardant (IFR) on polypropylene/ethylene‐propylene‐diene monomer (PP/EPDM) composites was researched using an elongational flow field. The results were then compared to shear flow field. The flame retardant mechanism was characterized using thermogravimetric‐Fourier transform infrared spectroscopy (TG‐FTIR). Furthermore, the flame retardant properties and morphologies of the composites using different flow fields were characterized using cone calorimeter (CC), limited oxygen index (LOI), vertical combustion test (VCT), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results indicated that the mixture of 1 wt% Nano‐ZnO and 29 wt% IFR which based on the elongational flow field (VZ1) catalyzed the esterification and charring effect more efficiently than that based on the shear flow field (TZ1). The TGA indicated that VZ1 exhibited higher decomposition temperature, and resulted in more char residues than those for TZ1. Furthermore, VZ1 resulted in longer delay for the ignition, and the ignition time was 105 s longer than that for TZ1, which was the longest of all samples. The fire performance index (FPI) was the highest, while the fire growth index (FGI) was the second lowest of all the samples, and resulted in the smallest fire. The digital photos showed that the char layer of VZ1 was more compact than that of TZ1. With the proposed flame retardant exhibited better dispersion and unique “bee‐comb” microstructure in the matrix through elongational flow field, and showed better retarding characteristics than that using shear flow field. POLYM. COMPOS., 40:2819–2833, 2019. © 2018 Society of Plastics Engineers