Multifractal analysis of tensile toughness and filler dispersion for polypropylene–CaCO3 composites

Multifractal analyses were performed to elucidate the effect of incorporating maleic anhydride grafted polypropylene (MAPP) into a Polypropylene matrix: (i) on the dispersion of CaCO3 particles and (ii) on the fracture morphology of tensile samples. The box-counting method was applied considering the number of particles and the mean gray value distribution as measured properties of composites. The dispersion analysis exhibited, for the composite with MAPP, a reduction of larger agglomerates sizes without variation of the most frequent size. Similar results were achieved by a typical particle size distribution. Moreover, the morphology of fractured surfaces showed an irregular topography for composites without MAPP suggesting a complex fracture process. Composites with MAPP, on the contrary, displayed a regular surface morphology suggesting a more regular fracture process with an important reduction of ductile mechanisms. This fracture behavior was related to the variation of the singularity width Δα. The results obtained suggest that multifractal theory can be applied to elucidate the relationship between structure and mechanical behavior of PP–CaCO3 composite materials.