SYNOPSISThe skin-core morphology of injection-molded polypropylene bars has been investigated employing X-ray small-and wide-angle scattering. The small-angle scattering has been evaluated by means of interface distribution functions. It is found that skin and core exhibit different morphologies. In the skin, the crystal lamellae are oriented primarily around the c axis, but a (small) fraction of a*-axis-oriented lamellae also exists. The lamellar thickness in the skin layer measured from the meridional small-angle X-ray scattering shows higher values than in the core. The composition of the monoclinic a l , a2 crystal modifications show dependencies that are typical for the cooling conditions in the mold during injection.

Blends of isotactic polypropylene with amorphous and slightly crystalline ethylene‐propylene‐diene terpolymer (EPDM), prepared by solution blending, have been investigated by optical microscopy and differential scanning calorimetry. Nucleation and crystallization kinetic parameters, such as nucleation rates, nucleation half times, Avrami‐exponents and spherulitic growth rates, have been determined. It has been found that the dispersion of crystalline EPDM in iPP is different from that of amorphous EPDM. Both EPDMs are incorporated into the spherulites, causing a decrease of the maximum growth rate of the iPP spherulites. The surface free energy of the iPP crystals is diminished on adding EPDM to iPP and is accompanied by a higher secondary nucleation rate. From the decrease observed in the Avrami exponent with increasing EPDM concentration in the blend, it has been concluded that nucleation becomes predominantly heterogeneous, as there is a proportional increase in the interfacial area between the two components.

The superstructure of PPO/iPS blends, in which the iPS is partially crystallized from the glassy state by thermal treatment, is studied as a function of composition. A superstructure model, based on Hosemann’s treatment of a linear paracrystalline lattice, is used in order to calculate theoretical SAXS curves and fit them with experimental SAXS data. The model includes such superstructure parameters as lamellae thicknesses, thicknesses of amorphous regions, thickness distribution function, and size and shape of ’’ordered’’ regions. It is found that the lattice thickness distribution functions for both the crystalline lamellae and amorphous layers are best represented by symmetrical Gaussian functions. The thickness of the iPS crystal lamellae decreases with increasing PPO content. This explains, in part, the observed decrease of the melting point of the iPS in these blends.

SynopsisSmall-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) as well as smallangle light-scattering (SALS) techniques have been applied to investigate the microstructure of a number of commercial poly(viny1 chloride) (PVC) samples. From the wide-angle x-ray scattering, crystallinity and crystal size parameters have been determined. The crystallinity of the samples investigated range from 5% to 10%. Superstructure parameters such as crystallite thickness, distribution functions of crystallite and amorphous thicknesses, and size of ordered regions have been obtained by an analysis of the SAXS curves using the cluster model. The crystallinity agrees well with the WAXS crystallinities indicating that most of the crystals are lamellar shaped, though some rodlike entities are present in the sample as is shown by the small-angle light scattering. From the SAXS analysis, the microstructure is described as clusters of lamella stacks which are identical with the subprimary particles. Their size is determined to be 220-240 A. Emulsion type PVC also contains lamellar-shaped crystals. The superstructure, however, of this type of PVC is different from that of mass or suspension-polymerized material. The SAXS curve does not reveal any correlation between the crystals.

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