Assessment of the addition of mineral fillers on the flammability, morphological and thermal properties of polypropylene

Abstract

Fire safety is a growing concern in the materials industry, leading to a study exploring the sustainable use of mineral fillers in polymeric materials. Polypropylene (PP) plates were developed with non-halogenated flame retardants, such as muscovite mica, titanium dioxide, and ammonium polyphosphate (APP). Sample preparation involved a Haake rheometer and compression molding. Material characterization included scanning electron microscopy, thermogravimetry, flammability testing, thermal conductivity, and specific gravity. Morphological analysis showed filler’s dispersion in the PP matrix. Thermogravimetric analysis revealed higher thermal degradation temperatures in samples with inorganic fillers compared to PP. The pyrolysis index of PP/TiO₂ and PP/Mica was roughly one-fourth that of PP/APP and about half that of the PP sample. During fire reaction testing, none of the samples exhibited flame retardant behavior according to UL-94, but PP/TiO₂ plates formed a char on the surface. The additives do not alter the thermal conductivity of the plates, making them suitable as thermal insulators. Specific gravity evaluation revealed a 3.3% increase in density for PP/APP plates compared to PP, while PP/Mica and PP/TiO₂ plates increased 28.4% and 24.8%, respectively. These findings suggest the potential of the plates as insulating materials in the construction industry, highlighting TiO₂'s additive due to its char-forming properties.