Hajime Sadatoshi

Transmission Electron Microscopic Observation of Nascent Polypropylene Particles Using a New Staining Method

Zieglar-Natta polymerization using heterogeneous catalyst is the only major process for the production of highly stereospecific polypropylene, in which TiCl3 and supported catalysts are mainly used as industrial catalyst. The typical catalysts are the 10–30 μm particles consisting of loosely bound agglomerates of fine catalyst crysta1lites, several tens to several handreds of angstrom in diameter1–5. The growth of the polymer particles on such catalysts6–12 and their architecture1,13–15 have aroused much interest widely, from the scientific and industrial point of view. It has been generally accepted that nascent polymer particles may replicate the original catalyst particle, including the internal structure16.

Isothermal crystallization of syndiotactic poly(propylene-co-olefin)s

Abstract Isothermal crystallization of syndiotactic poly(propylene-co-olefin)s (olefin=ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene) was studied. The melting behavior of isothermally crystallized polymers was investigated by differential scanning calorimetry, and the equilibrium melting temperature (Tm0) was determined by Hoffman–Weeks plot. Crystallization rate and Avrami exponent of isothermally crystallized copolymers from the melt were measured by depolarized light intensity technique. The half time of crystallization (t1/2) was found to be dependent on the degree of supercooling (ΔT), but independent of the comonomer. The Avrami exponents (n) of copolymers were detected by the Avrami plot and the average n ranged from 2.0 to 2.8 for the primary crystallization process in any copolymer. The effect of isothermal crystallization temperature (Tc) on the crystalline structure of copolymers was studied by wide-angle X-ray diffraction (WAXD). The WAXD patterns of all the copolymers were similar to the pattern of Cell II in the syndiotactic polypropylene. The WAXD pattern of 1-butene copolymer with small amount of 1-butene indicated the existence of Cell III.

27. Morphology of Nascent Polypropylene Produced by MgCl2 Supported Ti Catalyst

Publisher Summary The present chapter discusses the microstructure of nascent polypropylene and propylene–ethylene impact copolymer produced by MgCl2-supported Ti catalyst and Mg-Ti catalyst, widely differing in polymer yield using electron microscopy. The variety in the morphology of the nascent impact copolymers can be considered to result from the distribution of the aggregation force in propylene prepolymer—that is, EP copolymer locates in the weaker boundary. Mg-Ti catalyst was synthesized by reducing titanium tetrabutoxide with n-butylmagnesium chloride in the presence of silicon tetraethoxide, and treating with diisobutyl phthalate, and then with a mixture of TiCl4, dibutylether, and diisobutyl phthalate. The present catalyst consists of active and less-active crystallites, and the polymer subparticles observed in samples A-1 through A-4 are primary polypropylene particles that grew on chiefly active crystallites. At the high polymer yield the less active catalyst crystallites are located near the boundary of the primary polypropylene particles. The growth of polypropylene with Mg-Ti catalyst is similar to that with TiCl3, except for the number of catalyst crystallites in the polymer subparticles at the low polymer yield and the presence of the catalyst crystallites near the boundary at the high polymer yield.