Tactic polypropylene

Subsequently, Takada et al.55) studied the molecular weight distribution of syndio-tactic polypropylenes produced with the soluble VC14/A1(C2H5)2C1 catalyst in heptane... 

When 4 was activated with B(C6F5)3 (molar ratio B Zr=l), under the same reaction conditions as with MAO, a highly iso tactic polypropylene (mmmm= 98%) was formed, contrary to the results obtained with MAO (Eq. 1). The activity of this catalytic system (1.2xl05g polymer-mol Zr -h ) is lower than the activity of the complex 4 activated with MAO. It is important to point out that complex 4 has a C2-symmetry octahedral geometry, suggesting that theoretically, when activated with MAO, an isotactic polypropylene should also be expected, as it was in the case of the boron-containing cocatalyst. 

FIGURE 2-12 Iso tactic polypropylene (planar zigzag conformation). 

Gussoni,M., Ciampelli,F. Structure of liquid iso tactic polypropylene from its vibrational spectrum. Spectrochim. Acta 23A, 301-311 (1967). 

Besides the bridging unit, the fluorenyl fragment offers many possibilities for the selective modification of the discrete complex structure by variation of type, number, and position of the substituents. The series shown in Figure 11 represents some selected com-plexes ° ° and the influence of various substituents on catalyst activity and molecular weight. All complexes produce, in combination with MAO, syndio-tactic polypropylene with fairly good activities and low molecular weights except complex 49, which almost reaches an activity of 900 kg of PP/g of Zr-h. 

Stereoregular polymers also have symmetrical structures, and the helices of isotactic polymers can be close-packed to produce highly crystalline material. Iso-tactic polypropylene is crystalline and an important fiber-forming polymer, whereas the atactic form has virtually no crystalline contort and has little value as a fiber indeed, it is considerably more elastomeric in nature. 

Rickert, S., Baer, E., 1978. Epitaxial crystallization of iso tactic polypropylene on alkali halide surfaces. 

Typical orientation diagram plots obtained by X-ray diffraction for hot drawn film melt spun fibres, and cold drawn films of iso tactic polypropylene are shown in Fig. 50. It is noted that the crystal orientation change is... 

There are three types of commercial polypropylene resins iso tactic polypropylene, random copolymer and impact copolymer. Both copolymer types use ethylene as comonomer, but otherwise differ significantly. 

Control of Molecular Weight and Chain-End Group in Tactic Polypropylenes... 

POST-POLYMERIZATION FUNCTIONALIZATION OF TACTIC POLYPROPYLENES BY NON-RADICAL-GRAFTING METHODS... 

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