Morphology and crystallization kinetics of G-resins and isotactic polypropylene

Isothermal crystallization and morphology of G-resin (GPP) and isotactic polypropylene (iPP) samples were investigated and compared using synchrotron small- and wide-angle X-ray scattering/diffraction (SAXS/WAXD) and differential scanning calorimetry (DSC). Two GPP resins (MT12-s and MT18-s) are iPP containing a small amount of 1-butene. All polymers have similar MW and PDI, denoted by V30G, MT12-s, and MT18-s with 1-butene = 0.00, 6.43, and 5.20 wt%, respectively. DSC isothermal crystallization at 130 degrees C showed that the crystallinity of G resins were lower, but the crystallization rate of G resins was faster in the order as MT18-s >= MT12-s > V30G. Simultaneous synchrotron SAXS/WAXD was employed to determine polymer morphology crystallized from the melt. The electron density correlation function was calculated to estimate the lamellar thickness. The long periods (D) are around 19.0, 25.8, and 25.8 nm for V30G, MT12-s, and MT18-s, respectively. The GPP samples have a larger amorphous portion and a higher crystalline thickness (L) but a lower L/D ratio than IPP. The degree of crystallinity by WAXD is also smaller for GPP, that is, MT18-s (31%) approximate to MT12-s (31%) < V30G (>50%). In addition to the monoclinic alpha forms for all the PP samples, the orthorhombic gamma forms were found only for MT12-s and MT18-s. The crystallization of G-resins should be nucleated from the transparent filler and are not fully an intrinsic property of the copolymer chains.