Nascent polypropylene particles prepared with S-TiCl3 catalyst systems have been examined by small-angle X-ray scattering, wide-angle X-ray diffraction, and electron microscopy. The catalyst crystallites which disperse at the initial stage of polymerization uniformly within the polymer particles retain their initial size during the course of polymerization. As the polymerization proceeds, the 0.2-0.35-jtm primary polymer particles become visible under an electron microscope, and their size increases in proportion to the cube root of the polymer yield.

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This study clarifies and quantifies factors which increase the ductility of a low‐molecular‐weight propylene homopolymer having an intrinsic viscosity of 0.89 dl/g. The tensile behavior of homopolymer/ethylene‐propylene rubber (EPR) blends was studied from the viewpoint of the associated molecular structure of EPR and its compatibility with the homopolymer. When EPR is “dissolved” in a homopolymer, the glass transition temperature (Tg) of the amorphous phase of a homopolymer was found to shift to a lower temperature, with homopolymer/EPR compatibility being subsequently evaluated using this shift, i.e., Δtg. Results show two conditions are required to improve the ductility of the low‐molecular weight propylene homopolymer: ΔTg must be ≥ 3°C and ≥ 30 wt% EPR must be blended with the homopolymer.

Small-angle X-ray scattering (SAXS) analysis using MoK, radiation is successfully applied to a determination of the crystallite sizes of TiCI, catalysts. The sizes of TiCI, catalysts dispersed in nascent polypropylenes differing in polymer yield are determined by using this technique. It : s shown that the original catalyst size does not change during the course of polymerization. This result agrees with the observation by transmission electron microscopy (TEM).