20.500.12556/RUL-167831 Isotactic polypropylene (iPP) foils correlation of core and shell crystallinity with mechanical properties obtained by nanoindentation This study investigates the correlation between the crystallinity and mechanical properties of calendered isotactic polypropylene (iPP) foils, focusing on the influence of haul-off speed and additive type. Two groups of iPP foils produced on an industrial scale were compared: (i) foils containing 10 wt.% recycled PP at haul-off speeds of 2 and 10 m/min; and (ii) foils with different additives (neat PP, 10 wt.% recycled PP, and PP ran- dom copolymer) at a constant haul-off speed of 10 m/min. All foils exhibited a pronounced skin–core structure, with the inner surface showing higher crystallinity (up to 10%) due to slower cooling rates, as determined by Flash Differential Scanning Calorimetry (Flash DSC). Nanoindentation tests correlated these differences in crystallinity with variations in the hardness and elastic modulus across the cross-section of the foil. Higher haul-off speeds (10 m/min) resulted in increased crystallinity, a higher elastic modulus and higher hardness. Polarized optical microscopy (POM) confirmed the morphological differences and highlighted the presence of highly oriented skin layers and stratified crystalline struc- tures. These findings emphasize the significant influence of processing conditions, such as hauling speed and the addition of recycled polypropylene or a random copolymer, on the mechanical and optical properties of iPP foils. This comprehensive approach to characterizing complex structure–property relationships is valuable for optimizing the production and performance of polypropylene-based packaging foils on an industrial scale. isotactic polypropylene (iPP) foils calendering flash differential scanning calorimetry (Flash DSC) nanoindentation polarized optical microscopy crystallinity haze izotaktični polipropilen (iPP) folije kalandriranje hitra diferenčna dinamična kalorimetrija (Flash DSC) nanoindentacija polarizacijska optična mikroskopija kristaliničnost motnost true false false Angleški jezik Slovenski jezik Neznano 2025-03-14 12:08:53 2025-03-14 12:08:59 2025-03-15 04:06:38 0000-00-00 00:00:00 2025 0 0 18 str. no. 6, art. 736 Vol. 17 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2025-03-11 621 2073-4360 10.3390/polym17060736 229024771 RAZ_Huskic_Miroslav_2025.pdf RAZ_Huskic_Miroslav_2025.pdf 1 EA5DF746F2CFEBB05B075138581531A5 ed853fb23f2dfaead2739ee2a60d7ab02411e9f9fc26c1cf65da0a6438cdb2a4 183cb031-00c4-11f0-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=200648 https://www.mdpi.com/2073-4360/17/6/736 1 be305b78-00c3-11f0-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=200647 Fakulteta za strojništvo 0 0 0