Polypropylene preparation

Polyoxotungstates, 41 193 Polyoxovanadates, 41 193 Polyoxygen species, 32 115 Polypropylenes, preparation and properties of, 23 299-302... 

Table 1, Stereoregularities and molecular weights of polypropylenes prepared with different soluble vanadium-based catalysts at —78 °C... 

The syndiotactic polypropylenes prepared with soluble vanadium-based catalysts usually contain some irregular linkages of propylene units arranged in head-to-head (Eq. 31) and tail-to-tail (Eq. 32) sequences. Doi95) has shown that the syndiotactic triad fraction [rr] of polypropylene decreases with an increase of the amount of the irregular linkages of propylene units [F01 + F10] (see Figure 16). 

When propylene unit inversion is low as in the case of living polypropylene prepared with the soluble V(acac)3/A1(C2HS)2C1 catalyst, a typical propagating chain consists of short sequence blocks of 0 units and longer sequence blocks of 1 units, as represented by... 

Another rule that manifests itself is that polypropylene, produced with TiCh-containing precipitate reduced at 170° C., normally has a lower hexane soluble polymer content than polypropylene prepared with corresponding catalysts based on TiCL reduced at 80° C. 

Fig. 11 13C-NMR spectrum of the elastomeric polypropylene prepared with the catalytic system 14/MAO [119]...

Three types of elastomeric polypropylene are known (1) a large molecular weight atactic polymer [125], (2) polymers with alternating isotactic and atactic blocks [108,109,126-129], and (3) polymers formed by the dual-site mechanism [110]. The structure of the obtained elastomeric polypropylene was elucidated by comparison of the 13C-NMR spectra with those of an atactic oily polymer and isotactic polypropylene prepared by the zirconium complex 4. On the basis of the NMR data, for all the samples the statistical lengths of the isotactic blocks between two neighboring epimerization stereodefects were calculated [41]. It was found that for the isotactic polymer 90%), the... 

For polypropylene prepared with the catalytic system S-TiClj—Al( CH3)2l only end groups enriched by in the CHj fragments with prevailing threo-configuration were found These data are not compatible with the carbene mechanism. 

The phenomena observed were attributed to the different electron acceptor power of the aluminum compounds in agreement with the hypotheses of Henrici-Olive and Olive It was also observed examining the isotactic fraction of polypropylene prepared with S-TiClj and various aluminum alkyls, that M WD width depends on the nature of the ligand and specifically that it decreases in this order ... 

Rishina and Vizen observed that the MWD of the atactic fraction of polypropylene prepared with the 5-TiCl3—Al(C2H5)3 catalytic system narrows when polymerization temperature increased from 20 to 70 °C. This phenomenon was ascribed to a greater reactivity of the active centres for growing chain termination. 

Taylor and Tung reached the same conclusions for polyethylene prepared with TiCl4—Al(i-C.jH,)3, Keii for polypropylene prepared with MgClj-supported... 

Recently Yuan et al. reported that polypropylene, prepared with TiCla 1 /3AICI3... 

On the other hand, by fractionating isotactic polypropylene prepared in the presence of hydrogen with a-TiCl3—A1(C2H5)3, Pegoraro found polydispersity values lower than those observed by other researchers in the absence of hydrogen. 

The heptane-insoluble portion of polypropylene prepared with the ethylene-bis(l-indenyl)zirconium dichloride (11) catalyst at 0°C was found to crystallize in the y (70 %) and a modifications (30 %). The formation of the y modification is attributed to a small portion of 2,1-regioerrors and the quite unusual 1,3-misin-sertions [47, 48]. 

Shiomura, T. Uchikawa, N. Asanuma, T. Sugimoto, R. Fujio, I. Kimura, S. Harima, S. Akiyama, M. Kohno, M. Inoue, N. Metallocene-catalyzed Syndiotactic Polypropylene Preparation and Properties. In Metallocene-based Polyolefins Preparation, Properties and Technology, Scheirs, J., Kaminsky, W., Eds. Wiley Chichester, 2000 Vol. 1, p 467. 

Kakugo, M. Miyatake, T. Naito, Y. Mizunuma, K. Microtacticity distribution of polypropylene prepared with heterogeneous Ziegler-Natta catalysts. Macromolecules 1988, 21, 314-319. 

Fig. 12. I3C NMR spectra of boiling heptane-soluble and boiling pentane-insoluble fraction of polypropylene prepared with (a) 6-TiCl3-Al(13CH3)2I (b) 6-TiCl3-Al(13CH3)3-Zn(nCH3)2 (c) 6-TiClrAl(l3CH2CH3)3-Zn(13CH2CH3)2. The asterisked resonances are due to 13C-enriched carbons of the end-group.

It is worth examining this phenomenon in more depth. We have measured the following molar absorptivities e (average of five determinations differing from each other by less than +1.5%) for ether extracts of polypropylenes prepared by various catalyst systems (89) ... 

Termination involving these radicals could also lead to alkanes and some olefins as well. The reason why initiation at polymer chain ends dominates in some works is not clear, and may be enlightened by pyrolysis studies of polypropylene prepared by initiation with different alkyls such as Al(Me)3, Al(Et)3, or Al(iBu)3. 

Kim, S.J. Moon, J.B. Kim, G.H. Ha, C.S. (2008). Mechanical Properties of Polypropylene/Natural Fiber Composites Comparison of Wood Fiber and Cotton Fiber. Polymer Testing, Vol.27, No. 7, (October 2008), pp. 801-806, ISSN 0142-9418 Kotek, J. Kelnar, L Studenovsky, M. Baldrian J. (2005). Chlorosulfonated polypropylene preparation and its application as a coupling agent in polypropylene-clay nanocomposites. Polymer, Vol. 46, No. 16, (June 2005), pp. 4876-4881, ISSN 0032-3861... 

Varga, J. (2002). Beta-modification of isotactic polypropylene Preparation, structure, processing, properties, and apvplication.. Macromol Sci, Phys. B., Vol. B41, Issue 4-6, pp.1121-1171. 

Figure 3.14 Correlation of crystallinity with stereoregularity of polypropylene prepared with a series of thiophene Cl/istj-bridged metallocenes. Reproduced from Ref. [90].

Mulhaupt and coworkers have reported the details of several studies related to the preparation of block copolymers from thiol, maleic acid and hydroxy-functional polypropylene prepared by a metallocene catalyst [157, 158]. The same group also reported the transformation of metallocene-mediated olefin polymerization to anionic polymerization by a novel consecutive chain-transfer reaction for the preparation of polypropylene-based block copolymers [159]. The latter were also... 

A) DSC heating curves of isotactic polypropylene, prepared by temperature gradient annealing, as a function of scanning rate (1) 1.25 (11) 2.5 (111) 5 ... 

Figure 8.1. A model thermoplastic IPN. Electron scanning micrograph of a binary (70/30) blend of EPM and polypropylene prepared by intensive mixing after extraction of the EPM phase with heptane. The sample was fractured under liquid nitrogen the bar is 1...

Despite numerous studies, the observation of LAM in other polymers proved elusive for quite some time (105,106). For isotactic polypropylene, LAM was not obtained imtil 25 years after the initial observation. The first LAM observation was for an isotactic polypropylene prepared under special conditions of extrusion and orientation (107). Both sample transparency and the preferential reduction in Rayleigh scattering made the observation possible (Fig. 10). LAM has now been observed in a number of polymer systems such as PTFE, polyoxy methylene, PEO,... 

Grassi, A. Zambelli, A. Resconi, L. Albizzati, E. Mazzocchi, R. Microstructure of isotactic polypropylene prepared with homogeneous catalysis Stereoregularity, regioregularity, and 1,3 insertion. Macromolecules 1988,27, 617-622. 

Polypropylenes Prepared Using a Perfluorophenyl Borate as Cocatalyst. 258... 

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