Fire retardancy of polypropylene composites reinforced with rice husks: From oxygen index measurements and cone calorimetry to large-scale single-burning-item tests

Abstract

Rice husks containing 12 wt % inorganic silica were incorporated together with halogen‐free fire retardants in a polypropylene matrix and extruded into facade profiles. An increase in the amount of rice husks resulted in an increase in the oxygen index. The cone calorimetry measurements showed that all of the fire retardants tested significantly reduced the peak heat‐release rate (pHRR) and maximum average rate of heat emission (MARHE) of the formulations and moderately reduced total heat release. The best results in terms of MARHE were achieved for the formulation including 24% melamine‐coated ammonium polyphosphate. pHRR and MARHE were reduced with increasing amount of rice husks. Single‐burning‐item (SBI) tests were performed for the extruded profiles based on rice husks and, for comparison, wood flour. In the best case, a B‐s2, d0 classification was obtained. The results obtained from cone calorimetry and SBI tests were in agreement. Inc. J. Appl. Polym. Sci. 2018, 135, 46654.