Morphology and crystallization kinetics of G‐resins and isotactic polypropylene

Abstract

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 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%) ≈ MT12-s (31%) < V30G (>50%). In addition to the monoclinic α forms for all the PP samples, the orthorhombic γ 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.

Exploitation of a New Nucleating Agent by Molecular Structure Modification of Aryl Phosphate and Its Effect on Application Properties of the Polypropylene

“…Furthermore, PP is gaining more and more attention due to its favorable advantages of low cost, rich raw material source, easy processing, chemical resistance and good solvent resistance [ 5 , 6 , 7 ]. However, the crystallization rate of PP is low, and the large-size crystal leads to the disadvantages of PP materials such as time-consuming molding, poor transparency, and poor low-temperature impact resistance [ 8 , 9 , 10 ]. When used in different end-use domains, good crystallization property and mechanical properties for PP are generally required during mold processing.…”