Hideharu Mori

Polypropylene-block-poly(ethylene-co-propylene) addition to polypropylene/poly(ethylene-co-propylene) blends: morphology and mechanical properties

Abstract The additive effects of a diblock copolymer of polypropylene and ethylene–propylene rubber PP- b -EPR(50–50) on the morphology and mechanical properties of PP/EPR(50/50) blends were investigated. It was found from an electron microscopy study that the block copolymer is compatible with the PP phase but incompatible with the EPR phase. Dynamic mechanical spectra showed that the PP- b -EPR block copolymers are incorporated into the PP phase, and consequently, the EPR portions of the block are trapped into the interlamellae of PP.

Direct observation of MgCl2‐supported Ziegler catalysts by high resolution transmission electron microscopy

The surface atomic structure of MgCl 2 crystalline particles and MgCl 2 -supported Ziegler catalysts was observed by means of high resolution transmission electron microscopy. Step-terrace surface structures, characteristic of the structure of the MgCl 2 crystal, are found in the observed images of MgCl 2 particles. The observation of the structure of MgCl 2 -suuported Ziegler catalysts shows that the MgCl 2 crystals are severely deformed by the processes of catalyst preparation. Due to the preparation procedure used the structure of the catalyst changes from crystalline to amorphous

XPS study of the interaction of titanium species with internal electron donors on MgCl2-supported Ziegler catalysts

Abstract Two types of MgCl2-supported Ziegler catalysts prepared by a similar procedure with different internal electron donors were analyzed using X-ray photoelectron spectroscopy (XPS) to elucidate the interaction of the titanium species with the internal donors. The XPS measurement was also performed with an internal donor-free supported catalyst and TiCl4·ester complexes. The binding energies the Ti2p3/2 peak in the three supported catalysts were almost the same in spite of the difference in the internal donor. The higher values of the binding energy in the TiCl4·ester complexes, compared with the supported catalysts, indicated that the TiCl4·internal donor complex itself did not exist on the surface of the supported catalysts. The comparison of the binding energies among the supported catalysts after the reaction with triethylaluminium (TEA) showed that the reduction of the titanium species on the supported catalysts proceeded at the same level, regardless of the kind of the internal donor and of the catalyst preparation method. From the results obtained in this study, it was concluded that the internal electron donor existed free from titanium species on the supported catalysts, but the nature of the active sites was affected by the change in the environment through the interaction of the donor with MgCl2.

Variation in oxidation state of titanium species on MgCl2-supported Ziegler catalyst and its correlation with kinetic behavior for propylene polymerization

Abstract The variation in the oxidation state of the titanium species after reaction with various alkylaluminiums was investigated by X-ray photoelectron spectroscopy (XPS). The reaction of an MgCl2-supported Ziegler catalyst with alkylaluminium was observed to induce a chemical shift to lower binding energy and a broadening of the full width at half maximum intensity (FWHM), depending upon the kind of alkylaluminium. The polymerization kinetics was examined for slurry and stopped-flow polymerization to estimate the relationship between polymerization stages. The catalyst activation and the decay during the polymerization were found to be related to the variation in the titanium species arising from various alkylaluminium compounds.

X-ray photoelectron spectroscopy analysis for oxidation states of titanium chloride on the surface of Ziegler-Natta catalysts

Abstract X-ray photoelectron spectroscopy was applied for Ziegler-Natta catalysts and the oxidation state of titanium chloride was studied from the analysis of the Ti 2 p 3 2 peak. It was observed that the state of titanium chloride on the catalysts was changed by the reaction with the co-catalyst.

Stopped‐flow study of the interaction of MgCl2‐supported Ziegler catalyst with (Me)nSi(OEt)4‐n: a tool for understanding the active sites precursors and the correlation to stereospecificity

The active sites precursors on a MgCl 2 -supported Ziegler catalyst and the correlation to catalyst stereospecificity were investigated in the initial stage of propene polymerization in terms of the interaction of a variety of ethoxysilanes with the structure (Me) n Si(OEt) 4-n . The kinetic study using the stopped-flow technique indicated that the interaction of the catalyst with a variety of ethoxysilanes prevents formation of active sites, and the degree of inhibition depends upon the number of ethoxy groups. It is considered that the values of propagation rate constant on the isospecific active sites are essentially the same regardless of the structure of the ethoxysilane, but the ratio of the isospecific active sites to the total number of active sites depends on the number of ethoxy groups. The same tendency in the variation of the activity, the stereospecificity, and the kinetic parameters depending on the number of ethoxy groups attached to a silane atom was observed regardless of whether the ethoxysilanes were treated with the catalyst or with triethylaluminium before polymerization.

Study of thermo-oxidative degradation of molten state polypropylenes with a variety of tacticities

Thermo-oxidative degradation of polypropylene(PP)s with a variety of tacticities was investigated in terms of various degradation factors, such as catalyst residue in the PP and molecular weight of the PP. Heat treatment was typically carried out in air at 200°C for 30 min, where the PP powder was converted to a molten state within several minutes. The catalyst residue and molecular weight had a slight influence on the thermo-oxidative degradation of isotactic PP (iso-PP). The thermal stabilities of three PPs [iso-PP, atactic PP (ata-PP), and syndiotactic PP (syn-PP)] having similar molecular weights were investigated under the same conditions. Iso-PP was degraded drastically in air compared with ata-PP and syn-PP. Thus, it was found that the influence of the tacticity was significant compared with that of the catalyst residue and molecular weight.

Synthesis and basic characteristics of polypropene-block-poly(ethene-co-propene) by modified stopped-flow polymerization with an MgCl2-supported Ziegler catalyst

A well-defined diblock copolymer, polypropene-block-poly(ethene-co-propene) was synthesized by modified stopped-flow polymerization with an MgCl 2 -supported Ziegler catalyst. The copolymer shows a unimodal gel permeation chromatography (GPC) elution curve without any material in the low molecular weight region. The molecular weight can be controlled by the polymerization time (ca. 0.1 to 0.2 s). Furthermore, the elution pattern by cross fractionation chromatography showed that the block copolymer eluted at each temperature region between 0°C to 120 C is composed of a uniform material. After extraction with heptane, the 13 C NMR spectra showed that the signals from poly(ethene-co-propene) remain unchanged in the block copolymer but are absent in a corresponding polypropene/poly(ethene-co-propene) blend. The results of differential scanning calorimetry (DSC) and optical microscopic observation indicate not only the formation of a block copolymer with a chemical linkage between the polypropene block and the poly(ethene-co-propene) block, but also the regulation of the crystalline morphology in the block copolymer by changing the composition.

Blood compatibility of polypropylene surfaces in relation to the crystalline-amorphous microstructure.

Blood-contacting properties of polypropylene surfaces with different crystalline states at the surface layer were examined in terms of plasma protein adsorption and changes in cytoplasmic free Ca2+ levels in platelets. Though the wettability of polypropylene surfaces was almost constantly independent from the surface layer crystallinity and interlamellar spacing, an increase in adhesiveness was observed with decreasing surface layer crystallinity and interlamellar spacing. It is suggested that the surface properties of the sheets varied in relation to the crystalline-amorphous microstructure. Minimum magnitudes in albumin and fibrinogen adsorption were observed on the polypropylene surface with a particular surface layer crystallinity (c. 55 wt%). A decrease in interlamellar spacing resulted in enhancing albumin adsorption and diminishing fibrinogen adsorption. Transient phenomena in plasma protein adsorption were observed on their surfaces with a plasma concentration. It is considered that the polypropylene surface with a particular crystalline-amorphous microstructure reduces the denaturation of adsorbed proteins. An increase in cytoplasmic free Ca2+ levels in platelets was prevented at the polypropylene surface with a surface layer crystallinity of 55 wt%: the particular crystalline-amorphous microstructure of such apolar surfaces as polypropylenes acts to reduce platelet activation. Thus, it is concluded that the blood compatibility of polypropylene surfaces is greatly improved by controlling a crystalline-amorphous microstructure at the surface layer.

Deviation of hydrogen response during propylene polymerization with various Ziegler-Natta catalysts

Abstract The influence of the catalyst type on the hydrogen response during propylene polymerization with Ziegler–Natta catalysts was investigated in terms of the variations in kinetic behavior, catalyst activity, molecular weight and its distribution, and microstructure of the resulting polymers. Three different types of supported Ziegler catalysts and a TiCl 3 catalyst were used in this study. In all cases, the catalyst activity was found to significantly increase with the addition of hydrogen along with a sharp decrease in the molecular weights. The activity enhancement by hydrogen was remarkable during polymerizations with supported catalysts compared to the case of a TiCl 3 catalyst system. Hydrogen was found to activate all of the supported catalysts to same degree, regardless of the type of internal donor and the preparation method. This phenomenon is considered to be mainly ascribed to no significant difference in the number of dormant sites formed on the supported catalysts. The influence of the catalyst type on the hydrogen response was remarkable for the molecular weight and its distributions, which may be due to the difference in the states of the active species on each catalyst.