Structure of spherulite in Polybutene-1 investigated by wide angle X-ray scattering computed tomography

Investigating the structure of spherulite is instructive for better understanding the polymer crystallization process and mechanism, which is critical for the design and manufacture of polymeric products with high performance. Wide angle X-ray scattering computed tomography (WAXS-CT), a novel nondestructive method with ability of spatial resolution, is developed and applied to characterize the structure of spherulite in Polybutene-1 (PB-1). Spatial distribution of scattering intensity for 5 lattice-planes in PB-1 spherulite has been successfully extracted and depicted by reconstruction. The crystal lamellae orientations, derived from the scattering intensity for various lattice-planes, roughly shows a reasonable radial distribution from center to periphery in the spherulite. This distribution makes each lattice-plane can be observed by the WAXS scanning more easily at some specific positions in the spherulite. For example, lattice-planes (220) and (511) are easy to be observed in the periphery of spherulite, while lattice-plane (212) are apt to be observed in the spherulite center. The crystal orientation distribution also showcases the irregular branching during the growth of spherulite. Interestingly, the degree of crystallization is observed to increase first and then decrease along the radial direction of spherulite. This variation well mirrors the molecular segregation in the crystallization and the branching during the spherulite growth. Here, the results revealed by WAXS-CT can provide a new perspective for comprehending the internal structure and formation mechanism of PB-1 spherulite.