“…Regarding the drawn PP fibers, various fillers have been implemented, which can be classified in three main categories, i.e., carbonaceous fillers, mineral clays and other inorganic nanoparticles [ 27 ]. The first category includes graphene nanoplatelets [ 28 , 29 ], multi- or single- wall carbon nanotubes [ 14 , 19 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ], or carbon nanofibers [ 18 , 41 ]. Mineral clay fillers include montmorillonite, either modified [ 42 , 43 , 44 , 45 , 46 ], or not [ 42 , 46 ], synthetic modified hectorite [ 47 ], modified hydrotalcite [ 44 ], boehmite [ 48 ] and wollastonite [ 14 ].…”