Crystallization of the γ‐form of isotactic poly(propylene)

Marigo, Antonio; Marega, Carla; Zannetti, Roberto; Paganetto, Guglielmo; Canossa, E.; Coletta, Flaviano; Gottardi, Francesca

doi:10.1002/macp.1989.021901112

Cited by 54 publications

(30 citation statements)

References 15 publications

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“…The model shown in Figure 3 predicts peaks on the equator (2␦ ϭ 180°) and at 2␦ ϭ 93.5°, in good agreement with the observed azimuthal intensity distribution in Figure 4 and demonstrating that Figure 3 correctly captures the relationship between the ␥-iPP lamellae and the fiber axis. Analogous calculations 27 for the azimuthal locations of the intensity maxima for the previously reported triclinic cells 5,6,17 yield results very similar to those from the orthorhombic cell, which is not surprising, because both unit cells were formulated to be consistent with very similar powder X-ray and single-crystal electron diffraction data. Details of the calculations may be found elsewhere; 27 although the azimuthal positions of the reflections are calculated to be indistinguishable for the orthorhombic and triclinic cells, detailed fitting of the azimuthal intensity distribution supports the orthorhombic cell.…”

Section: Resultssupporting

confidence: 65%

“…Originally, the unit cell of ␥-iPP was reported as triclinic. 5,15 Subsequently, other groups reported evidence for the triclinic cell using both electron 16 and X-ray 17,18 diffraction. In 1989, a group using the Rietveld method of the X-ray powder pattern analysis proposed an orthorhombic structure with an unusual nonparallel arrangement of the polymer chains, 6,7 and in 1991 electron diffraction on single crystals of ␥-iPP confirmed the correctness of this orthorhombic cell over the earlier triclinic models.…”

Section: Introductionmentioning

confidence: 97%

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Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

Dean¹,

1998

J. Polym. Sci. B Polym. Phys.

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Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 97%

Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

Dean¹,

1998

J. Polym. Sci. B Polym. Phys.

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“…The concentrations of regio-defects were determined from their specific resonances. 30,33 The metallocene-catalyzed polymers listed in Table I can be conveniently placed in three groups, as is indicated. The polymers in group A have no stereo-defects, essentially a constant concentration of regio-defects, and a fourfold variation in molecular weight.…”

Section: Methodsmentioning

confidence: 99%

The degree of crystallinity of monoclinic isotactic poly(propylene)

Isasi

Mandelkern

Galante

et al. 1999

J. Polym. Sci. B Polym. Phys.

103

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The degree of crystallinity of a set of monoclinic (alpha) isotactic poly(propylenes), prepared by a metallocene‐type catalyst, were determined at room temperature. Three different methods were used: density, enthalpy of fusion, and wide‐angle X‐ray scattering, and the results compared. The relation between the heat of fusion and the specific volume of these poly(propylenes) was found to be nonlinear, thus precluding any linear extrapolation to obtain the heat of fusion of the pure crystal (ΔHu). The value of ΔHu obtained from depression of the melting temperature by diluents is used. Based on the unit cell density of monoclinic crystals formed from a low defected fraction, the density obtained crystallinity levels were found to be between 0.l5–0.25 higher than those calculated from the heat of fusion. This relatively large difference holds for the isothermally crystallized and quenched isotactic poly(propylenes), and reflects the contribution of the interphase to the density determined crystallinity, which does not contribute to the heat of fusion. Paralleling results found in other systems, the crystallinity levels obtained from wide‐angle X‐ray scattering agree with those obtained from density, indicating a significant contribution of the partially ordered phase to the total diffraction. Emphasis is given on the need to account for the large differences in the crystallinities of poly(propylene) measured by different techniques when evaluating the dependence of properties on this quantity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 323–334, 1999

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“…More specifically, the tions 17-24 and the amount of structural irregularities in the chain. 25,26 Among these three crystaleffect of the concentration and type of defect, the molecular weight and the crystallization condiline structures, the monoclinic ( a) form is by far the most common and most extensively studied tions on the expansion of the a (monoclinic) unit cell are investigated. Although metallocene-type over the last 35 years.…”

Section: Introductionmentioning

confidence: 99%

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

Isasi

Alamo

Mandelkern

1997

J. Polym. Sci. B Polym. Phys.

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The lattice parameters of a series of monoclinic metallocene poly(propylenes) of constant molecular weight are measured as a function of defect content, that vary between 0.3 and 2.35 total defects per 100 monomeric units. The parameters are also measured as a function of molecular weight for a fixed defect content and as a function of the crystallization temperature. The b axis is found to increase with decreasing isothermal crystallization temperature whereas only small changes are found for samples rapidly crystallized. The a and c axis showed basically no variation with crystallization temperature. The parameters of the unit cell were essentially constant with varying defect content in the poly(propylene) chain. Lack of observed effect on the dilation of the unit cell by increasing defects is a consequence of the rapid crystallization required to ensure formation of monoclinic crystals. The unit cell parameters increased as a mild function of the molecular weight. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2511–2521, 1997

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Crystallization of the γ‐form of isotactic poly(propylene)

Cited by 54 publications

References 15 publications

Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

The degree of crystallinity of monoclinic isotactic poly(propylene)

A study of the dilation of the unit cell of metallocene isotactic poly(propylenes): The monoclinic form

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