Effects of melt structure on shear-induced β-cylindrites of isotactic polypropylene

摘要: Abstract The effects of melt structure and shear flow on the polymorphic nature β-cylindrites were investigated by means wide angle X-ray diffraction (WAXD), small scattering (SAXS), polarized light microscopy (PLM), differential scanning calorimeter (DSC), Scanning Electron Microscope (SEM). temperature-resolved SAXS/WAXD experiments indicate that NMP (near melting point) process (the annealing temperature between T m “the nominal temperatures” 0 equilibrium temperature”) erases polymer crystalline unit lattice, however, lamellar structures iPP can survive in this for long time, even (partially melting) above . We call incomplete relaxed (include survived structures) as “ordered melt”. observations from SAXS ordered suggest 167 180 °C, period ( L ) increases 29.2 to 48.9 nm (Strobl method) thickness d c 9.2 12.9 nm with increasing ∗ changed slightly time. In order study effect crystals after flow, shear-induced specimens prepared extruding near point (NMP) through capillary die. It was found that, only very low stress σ w  = 0.020 MPa) have been applied melt, be observed. Length number decreases  = 177–190 °C), content β-iPP remained almost invariant when set 177 obviously decreased. According results here we proposed formation β-cylindrites, it is suggested may remain which act shear-precursor during course recooling initiate crystallization. size density strongly influence partially temperature.