Abstract
Reactor powder of a number of commercial ultra-high molecular weight polyethylenes synthesized on heterogeneous Ziegler–Natta catalyst in a conventional slurry process have been investigated with the help of scanning electron microscopy (SEM), wide-angle x-ray scattering (WAXS), differential scanning calorimetry (DSC), and low-frequency Raman spectroscopy. The SEM study reveals a complicated structure of nascent particles consisting of a small (0.5–1.0 μm) spongy-like fibrillar spheres. It is suggested that the elementary morphological units are fibrils formed by the small defective crystallites with the dominating crystalline distortions caused by microstrains. The comparison of longitudinal crystallite sizes derived from WAXS data with the straight chain segment length calculated from Raman shift frequency and the length of extended segments computed from the true melting interval measured by DSC allows to conclude that there are a large number of extended tie chains bridging the neighboring crystallites, which is not in agreement with a lamellar model. The extended chains passing through the noncrystalline regions stabilize a structure and provides its thermal stability. A possible tilting of molecules in the crystals, the location of defects and the distribution of crystallite sizes are discussed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
