Polypropylene nanosphere: particle size and crystal structure

Abstract

The high molecular weight polypropylene (PP) nanospheres (average particles size ∼ 60 nm) were synthesized under controlled growth condition using Ziegler-Natta catalyst. The sizes of the PP particles were investigated through microscopy analysis. The size-dependent crystal structure and crystallinity were studied through X-Ray powder diffraction (XRD) and differential scanning calorimetry (DSC). At 25°C PP nanoparticles show higher crystallinity (∼76%) compared to the micron sized PP particles (∼59%). The rearrangement of polymer chains is the reason for the higher crystallinity of nanosphere PP particles. The periodic organization of PP chains inside the nanoparticles shows new peaks. These corroborate the presence of α-monoclinic phase. The α-crystalline lamella lengths of various particle sizes are calculated and found to be 14.5 nm for nanoparticles, whereas the same for the microsphere PP is 17.6 nm. The crystal domains consist of various sizes of α-monoclinic crystals. Moreover, the absence of γ-orthorhombic phase acknowledges that the PP nanospheres are composed of α-monoclinic crystal domains.