Investigation of the crystallization behavior of isotactic polypropylene polymerized with different Ziegler‐Natta catalysts

Abstract

Detailed characterization of the crystallization behavior is important for obtaining better structure property correlations of the isotactic polypropylene (iPP), however, attributed to the complexity in ZN-iPP polymerization, the relationship between crystallization behavior and the stereo-defect distribution of iPP is still under debate. In this study, the crystallization kinetics of the primary nucleation, crystal growth and overall crystallization of two iPP samples (PP-A and PP-B) with nearly same average isotacticity but different stereo-defect distribution (the stereo-defect distribution of PP-B is more uniform than PP-A) were investigated. The results of isothermal crystallization kinetics showed that the overall crystallization rate of PP-A was much higher than that of PP-B; but the analysis of self-nucleation isothermal crystallization kinetics and the polarized optical microscopy (POM) observation indicated that the high overall crystallization rate of PP-A was attributed to the high primary nucleation rate of the resin. The stereodefect distribution plays an important role in determining both the nucleation kinetics and crystal grow kinetics, and thus influence the overall crystallization kinetics. A more uniform distribution of stereo-defects restrains the crystallization rate of iPP, moreover, it has more influence on nucleation kinetics, comparing with the crystal growth.

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

“…Acceleration of the nucleation step can be accomplished by previous SN of the polymer. Under these conditions, the crystallization rate of self-nucleated material increases such that isothermal DSC can be performed [4,69,76,96,123,[139][140][141][142][143][144][145][146][147][148][149][150][151][152]. It is well known that overall crystallization kinetics obtained by isothermal DSC experiments contains both nucleation and growth components.…”

PLA/SiO2 composites: Influence of the filler modifications on the morphology, crystallization behavior, and mechanical properties

“…20 It has been established that the crystallization rate of PLA is the fastest between 100 and 120 8C under isothermal conditions. The crystallization half-time is the time interval from the crystallization onset (t 0 ) to the time to 50% completion.…”

Influence of melt structure on the crystallization behavior and polymorphic composition of polypropylene random copolymer

“…The temperature scale calibration was performed using indium as a standard to ensure reliability of the data obtained [51][52][53][54]. 5 mg round samples were used.…”