To obtain the specific surface area of the unaged particles, we analyzed the SEM images and utilized ImageJ for all samples except for PP-needles c . By using the ImageJ software, we measured the diameter (and in case of fibers also the length) of at least 100 particles per sample and calculated the corresponding surface area. For these calculations, we approximated particles as spherical and fibers as cylinders. For PP-needles c , characterized by dense, hay-like features (see Figure ), we employed N2 sorption measurements on an ASAP 2020 gas sorption instrument (Micromeritics) to obtain the Brunauer-Emmett-Teller (BET) specific surface area , since obtaining identifiable, individual particles from SEM images was challenging. Before analysis, the sample was degassed for 9 h at 90°C. We collected N2 sorption data at 77 K in the relative pressure range of 0-1 (saturation pressure 1 atm), and calculated the BET surface area using the BETSI software package.