Structure and properties of isotactic polypropylene

Natta, G.; Corradini, Paolo

doi:10.1007/bf02731859

Cited by 876 publications

(599 citation statements)

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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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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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“…It is seen that the XRD profiles of unannealed film (UA) in equatorial (EQ) and meridional (ME) scans consist of two intense broad peaks at 2 15.4 and 21.4 , respectively. This pattern has been well known as the "smectic phase" of PP as first observed by Natta and Coradini [16]. Generally, the smectic phase of PP can be transformed into the more stable crystalline phase ( -form) through annealing at proper temperature, i.e., 70-150 o C [22][23][24][25][26][27][28].…”

Section: Microstructure and Molecular Orientation Development During mentioning

confidence: 76%

“…Generally, the smectic phase of PP can be transformed into the more stable crystalline phase ( -form) through annealing at proper temperature, i.e., 70-150 o C [22][23][24][25][26][27][28]. While, the XRD profiles of annealed composite films in both EQ ( Figure 1a ) and ME ( Figure 1b [16,[24][25][26][27]. As the annealing time increases, the XRD intensity profiles in both sections are sharper and more intense, implying that the transformation of smectic phase into monoclinic phase is more pronounced with increasing annealing time [24][25][26][27].…”

Section: Microstructure and Molecular Orientation Development During mentioning

confidence: 99%

“…The applications of PP may extend by addition of fillers/nanoparticles [12,13] and/or blending with TPs [14,15] or LCP [1][2][3][4][5][6][7][8], in order to improve its mechanical properties. Besides, PP can also crystallize to four different forms depending on the crystallization conditions [16][17][18][19][20][21][22]: monoclinic α-phase, hexagonal β-phase, orthorhombic γ-phase and the so-called smectic phase. The α-phase is the stable crystalline form and is the most commonly observed under the usual crystallization conditions.…”

Section: Introductionmentioning

confidence: 99%

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correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP

Saengsuwan

2011

E-Polymers

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Drawn composite thin film based on thermotropic liquid crystalline polymer (TLCP) and polypropylene (PP) was annealed at 130 o C at different times. The influence of annealing time on microstructural and mechanical properties of the composite film has been studied. The correlation in mechanical properties and their microstructural parameters has also been investigated. X-Ray diffraction results reveal that the smectic mesophase transforms progressively into the monoclinic phase as annealing time is increased. Consequently, the true crystallinity (X c ), crystal thickness (L) as well as relative level of molecular orientation of PP crystalline phase in the annealed TLCP/PP films are increased significantly. Also, the TLCP fibrils have no influence on the microstructure of PP crystalline phase. The apparent crystallinity (X c,a ) of PP phase evaluated by DSC also increase significantly with annealing time. As a result, the increases of these microstructural parameters coupled with the reinforcement of TLCP fibrils could be contributed directly to the remarkable enhancement of mechanical properties of the annealed TLCP/PP film in both machine (MD) and transverse (TD) directions. The correlation of moduli with microstructural parameters (X c , X c,a and L) exhibits nonlinear relations. However, the relative level of molecular orientation is a more suitable parameter to correlate with the improvement of mechanical properties of the annealed TLCP/PP film. Finally, this work presents that the mechanical properties of the TLCP in situ reinforced thermoplastics can be significantly enhanced via a simple thermal treatment.

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“…Four different crystal phases can be present in stereoregular iPP. Most dominantly present is typically the α-phase [6], formed at atmospheric pressure and low to moderate cooling rate. Crystallization under the influence of moderately strong flow conditions or specific nucleating agents can induce the β-phase [7], whereas crystallization of the γ-phase can be achieved in several ways, such as inclusion of small amounts of 1-olefin co-units [8], introduction of stereo-and regio-irregularities controlled by a metallocene catalyst [9,10], use of materials of very low molecular weight [11], or crystallization under elevated pressure and high temperature [12,13].…”

Section: Introductionmentioning

confidence: 99%

Modeling Flow-Induced Crystallization

Roozemond

Drongelen

Peters

2016

Polymer Crystallization II

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A numerical model is presented that describes all aspects of flow-induced crystallization of isotactic polypropylene at high shear rates and elevated pressures. It incorporates nonlinear viscoelasticity, including viscosity change as a result of formation of oriented fibrillar crystals (shish), compressibility, and nonisothermal process conditions caused by shear heating and heat release as a result of crystallization. In the first part of this chapter, the model is validated with experimental data obtained in a channel flow geometry. Quantitative agreement between experimental results and the numerical model is observed in terms of pressure drop, apparent crystallinity, parent/daughter ratio, Hermans' orientation, and shear layer thickness. In the second part, the focus is on flow-induced crystallization of isotactic polypropylene at elevated pressures, resulting in multiple crystal phases and morphologies. All parameters but one are fixed a priori from the first part of the chapter. One additional parameter, determining the portion of β-crystal spherulites nucleated by flow, is introduced. By doing so, an accurate description of the fraction of β-phase crystals is obtained. The model accurately captures experimental data for fractions of all crystal phases over a wide range of flow conditions (shear rates from 0 to 200 s À1 , pressures from 100 to 1,200 bar, shear temperatures from 130 C to 180 C). Moreover, it is shown that, for high shear rates and pressures, the measured γ-phase fractions can only be matched if γ-crystals can nucleate directly on shish.

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Structure and properties of isotactic polypropylene

Cited by 876 publications

References 2 publications

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

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

correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP

Modeling Flow-Induced Crystallization

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