Assessment of Metallocene Propylene Polymers for Cast Film Applications

Lin, Ching-Yeh; Chen, M. C.; Mehta, Aspy

doi:10.1106/3c68-twxp-qmea-6ufk

Cited by 8 publications

(1 citation statement)

References 2 publications

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“…Advances in catalyst technology make it possible to synthesize polypropylenes and propylene copolymers that differ substantially in molecular weight and molecular weight distribution, in stereo defect type and distribution, and in comonomer distribution. It has been suggested that this unprecedented control of the molecular structure can lead to a set of differentiated properties of oriented film 1, 14, 15. In the present study, three isotactic polypropylene resins that differed in the chain architecture were biaxially oriented at various temperatures close to the peak melting temperature.…”

Section: Introductionmentioning

confidence: 75%

Effect of chain architecture on biaxial orientation and oxygen permeability of polypropylene film

Dias¹,

Yuan²,

Hiltner³

et al. 2007

J of Applied Polymer Sci

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Films of two isotactic propylene homopolymers prepared with different catalysts and a propylene/ ethylene copolymer were biaxially oriented under conditions of temperature and strain rate that were similar to those encountered in a commercial film process. The draw temperature was varied in the range between the onset of melting and the peak melting temperature. It was found that the stress response during stretching depended on the residual crystallinity in the same way for all three polymers. Biaxial orientation reduced the oxygen permeability of the oriented films, however, the reduction did not correlate with the amount of orientation as measured by birefringence, with the fraction of amorphous phase as determined by density, or with free volume hole size as determined by PALS. Rather, the decrease in permeability was attributed to reduced mobility of amorphous tie molecules. A single one-to-one correlation between the oxygen permeability and the intensity of the dynamic mechanical brelaxation was demonstrated for all the polymers used in the study.

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Section: Introductionmentioning

confidence: 75%

Effect of chain architecture on biaxial orientation and oxygen permeability of polypropylene film

Dias¹,

Yuan²,

Hiltner³

et al. 2007

J of Applied Polymer Sci

View full text Add to dashboard Cite

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Stress‐induced changes in microstructure of a low‐crystalline polypropylene investigated at uniaxial stretching

Böger

Heise

Marti

et al. 2008

J of Applied Polymer Sci

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Novel asymmetric metallocene catalysts lead to low isotactic polypropylenes (iPP) with randomly distributed stereo irregularities. The polypropylenes are low crystalline and show elastic mechanical behavior due to physical crosslinking. The morphology of such iPP, which is responsible for the observed mechanical properties, is still sparsely resolved. In the present work a low isotactic, low crystalline metallocene iPP containing randomly distributed stereoerrors was investigated. The influence of the chain microstructure in the elastic properties was studied using two complementary investigation methods, X-ray diffraction and scanning force microscopy (SFM). For a better understanding of the unique mechanical properties, microscopic changes in morphology and strain-induced variation in chain orientation were monitored during uniaxial stretching using SFM and wide angle X-ray scattering measurements. For quantitative analysis and discussion the polymer chain orientations were calculated. The correlation between the orientation, the arrangements of the amorphous and crystalline phases observed by SFM, and the mechanical properties of the material at different elongation ratios allowed an interpretation of the macroscopic behavior on the microscopic scale. It was shown that the deformation behavior of low isotactic polypropylene with randomly distributed stereoerrors is in agreement with existing structural models, which proposed that small crystalline domains act as physical crosslinks for the amorphous matrix.

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Flow‐induced morphology of cast polypropylene

Yin

Yang

et al. 2004

Polymer Engineering & Sci

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The crystal structures of different grades of cast polypropylene (CPP) extrudates were characterized by Differential Scanning Calorimetry (DSC) and Wide Angle X‐ray Diffraction (WAXD). The effects of the crystallization temperature, draw ratio, and cooling rate on crystal structure are discussed in detail. The results demonstrate that stretching cannot induce the formation of the γ crystal, but the crystallization temperature and the cooling rate do affect the formation of the γ crystal. The slower the cooling rate, the more easily the γ crystal develops. It was found that at the optimum crystallization temperature (Tc) of about 110°C, the γ crystal developed distinctly, and a slower cooling rate made the formation of γ crystal easier. Also, the crystal structures of different resins at the same conditions were discriminative, suggesting that the formation of the γ crystal was due to interruptions of comonomer units in the isotactic propylene sequences, which prevented the PP chain segment from entering the crystal lattice of the α crystal in some degree. If the length of the comonomer sequences was shorter and the distribution of the comonomer units more symmetrical, the formation of the γ crystal would be more distinct. Polym. Eng. Sci. 44:1656–1661, 2004. © 2004 Society of Plastics Engineers.

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Assessment of Metallocene Propylene Polymers for Cast Film Applications

Cited by 8 publications

References 2 publications

Effect of chain architecture on biaxial orientation and oxygen permeability of polypropylene film

Effect of chain architecture on biaxial orientation and oxygen permeability of polypropylene film

Stress‐induced changes in microstructure of a low‐crystalline polypropylene investigated at uniaxial stretching

Flow‐induced morphology of cast polypropylene

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