Structure of .beta.-Isotactic Polypropylene: A Long-Standing Structural Puzzle

Meille, Stefano Valdo; Ferro, Dino R.; Brueckner, S.; Lovinger, Andrew J.; Padden, F. J.

doi:10.1021/ma00087a034

Cited by 312 publications

(246 citation statements)

References 13 publications

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“…It is a well known fact that there are some crystal types of PP with different crystal systems, and surface roughness of BOPP films has been investigated in association with crystal types [2][3][4][5][6][7][8] . Many basic studies have been reported on the formation of α and β crystals [9][10][11][12][13][14] . Natta and Corradini reported in their report in 1960 that unit lattice of α crystal is the monoclinic system, and now it is known as being the most dominant crystal in PP 9) .…”

Section: Introductionmentioning

confidence: 99%

Crater formation mechanism on the surface of a biaxially oriented polypropylene film

Tamura¹,

Takino

Yamada

et al. 2012

J of Applied Polymer Sci

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Biaxially oriented polypropylene (BOPP) films are used in a variety of areas around the world. They are especially suited for food packaging and industrial usages due to their high productivity. Many studies on stretchability regarding crystal structure changes have been reported by various researchers, since the machine speed has been increasing and the demand to produce thinner films has been becoming more important.Furthermore, a number of studies on the surface structure of BOPP films with crater-like roughness have been reported since the 1980's. Although the crater-like surface roughness was formed under specific film process conditions, the formation mechanism and the controlling method of the crater-like film surface are yet to be clarified. In this report, the authors demonstrate a new hypothesis as to the crater-like film surface roughness formation mechanism by analyzing the morphology of the surface layer of polypropylene (PP) sheets and by investigating the relationship between the surface structure changes and the entire structure changes. As a result, it was found that it needs to have over critical crystallization time in order to form the crater on the surface of BOPP film, and the crater formation mechanism was closely related not only to the surface structure changes but also to the deforming phenomenon of spherulite in PP sheet during stretching. Furthermore, this report will show the controlling factors in the formation of the crater structure from the view point of production conditions.

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Section: Introductionmentioning

confidence: 99%

Crater formation mechanism on the surface of a biaxially oriented polypropylene film

Tamura¹,

Takino

Yamada

et al. 2012

J of Applied Polymer Sci

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show abstract

“…When crystallized from the molten state, iPP chains adopt a 3/1 helix, indicating that it takes three monomer units to make one helical turn. The iPP often presents three different crystalline forms, namely, the monoclinic α-modification, trigonal β-modification, and triclinic γ-modification, depending on the crystallization conditions [10][11][12][13][14][15][16][17]. Among these polymorphs, the α-form is the thermodynamically stable crystalline modification and is predominate under the usual crystallization conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Also, the wide angle X-ray diffraction (WAXD) patterns of α-form show the characteristic peaks at 2θ about 14.1 (110), 17.0 (040), 18.5 (130), 21.3 (111) and 21.8° (041) [3,5,11,12,18]. The β-form is less prevalent because of its lower stability than α-form and results from crystallization under a temperature gradient, under shear during processing or in the presence of specific nucleating agent [13][14][15]. Finally, the γ-form is the rarest and can be observed only sporadically, especially, only when low molecular weight iPP crystallizes under high pressure [16,17].…”

Section: Introductionmentioning

confidence: 99%

Influence of annealing on microstructure & molecular orientation, thermal behaviour, mechanical properties and their correlations of uniaxially drawn iPP thin film

Saengsuwan

2008

E-Polymers

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Abstract:The influence of annealing on the microstructure and molecular orientation, thermal behaviour and mechanical properties of uniaxially drawn iPP thin film was studied by wide-angle X-ray diffraction, differential scanning calorimetry and tensile testing, respectively. The correlations of mechanical and microstructural properties of annealed films were also examined. The transformation of smectic phase of iPP to the α-form was more pronounced with increasing annealing time and temperature. The true and apparent crystallinities and crystal thickness were strongly enhanced with annealing time and temperature. The relative molecular orientation tended to increase with annealing time. These results caused the significant improvement of modulus and tensile strength of the annealed films in both machine (MD) and transverse (TD) directions. The increases in MD-Young's modulus and MD-tensile strength were well correlated with the increase in true crystallinity obtained in equatorial scans. Some relationship between the increase in crystal thickness and the increase in Young's modulus in both MD and TD directions was also found.

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“…The deformation behavior of polypropylene has received renewed attention with recent developments in metallocene catalyst technology, which allows for tacticity control 39 and biaxially oriented polypropylenes, 5,40 resulting in superior properties. iPP is a richly polymorphic material that exhibits three well-documented crystalline forms (monoclinic ␣, 41,42 hexagonal ␤, [43][44][45] and triclinic ␥ 46 -49 ) as well as a paracrystalline "smectic" phase 50 -55 (generated via rapid quenching from the melt), each contributing differently to the physical properties of the material. The deformation behavior and the role of the crystalline phase on the tensile properties during deformation are addressed in great detail by Baltá -Calleja and Peterlin 56,57 and others.…”

Section: Introductionmentioning

confidence: 99%

Rheooptical Fourier transform infrared spectroscopy of the deformation behavior in quenched and slow‐cooled isotactic polypropylene films

Parthasarthy

Sevegney

Kannan

2002

J Polym Sci B Polym Phys

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Emerging technological applications for complex polymers require insight into the dynamics of these materials from a molecular and nanostructural viewpoint. To characterize the orientational response at these length scales, we developed a versatile rheooptical Fourier transform infrared (FTIR) spectrometer by combining rheometry, polarimetry, and FTIR spectroscopy. This instrument is capable of measuring linear infrared dichroism spectra during both small-strain dynamic deformation and large-strain irreversible deformation over a wide temperature range. The deformation response of quenched and slow-cooled isotactic polypropylene (iPP) is investigated. In quenched iPP, under dynamic oscillatory strain at an amplitude of ϳ0.1%, the dichroism from the orientation of the amorphous chains is appreciably less than that from the crystalline region. At large irreversible strains, we measured the dichroic response for 12 different peaks simultaneously and quantitatively. The dichroism from the crystalline peaks is strong as compared to amorphous peaks. In the quenched sample, the dichroism from the crystalline region saturates at 50% strain, followed by a significant increase in the amorphous region dichroism. This is consistent with the notion that the crystalline regions respond strongly before the yield point, whereas the majority of postyielding orientation occurs in the amorphous region. Our results also suggest that the 841 cm Ϫ1 peak may be especially sensitive to the 'smectic' region orientation in the quenched sample. The response of the slow-cooled sample at 70°C is qualitatively similar but characterized by a stronger crystalline region dichroism and a weaker amorphous region dichroism, consistent with the higher crystallinity of this sample, and faster chain relaxation at 70°C.

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Structure of .beta.-Isotactic Polypropylene: A Long-Standing Structural Puzzle

Cited by 312 publications

References 13 publications

Crater formation mechanism on the surface of a biaxially oriented polypropylene film

Crater formation mechanism on the surface of a biaxially oriented polypropylene film

Influence of annealing on microstructure & molecular orientation, thermal behaviour, mechanical properties and their correlations of uniaxially drawn iPP thin film

Rheooptical Fourier transform infrared spectroscopy of the deformation behavior in quenched and slow‐cooled isotactic polypropylene films

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