Shear-induced crystallization of isotactic polypropylene melts: isothermal WAXS experiments with synchrotron radiation

Moitzi, J.; Skalický, P.

doi:10.1016/0032-3861(93)90385-n

Cited by 70 publications

(49 citation statements)

References 16 publications

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“…In order to clarify the mechanism for the formation of the surface craters, PP-A of a high tacticitiy with a meso pentad mmmm value of 96mol% which is a parameter of the isotactic index measured by 13 C-NMR was prepared. Thermal properties of melting point (Tm), melting enthalpy (ΔHm), and crystallization temperature (Tc) were measured by differential scanning calorimetry (DSC, PerkinElmer B014-3018/B014-3003), and the molecular weight distribution parameter Mw/Mn was measured by gel permeation chromatography (GPC).…”

Section: ) Samplesmentioning

confidence: 99%

“…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%

“…β crystal was discovered by Keith in 1959, and the unit lattice is a hexagonal system 10) . It was reported that β crystals are formed easily by adding β nucleator into raw PP 11) , under the controlled temperature gradient 12) , and under a strong shear stress in the extruder such as at a low extruding temperature 13) .…”

Section: Introductionmentioning

confidence: 99%

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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: ) Samplesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…[20,21] Much research, involving the molecular weight-shear condition relationship on the shish kebab morphology, has focused on the important role of the high-molecularweight species in enhancing crystallization kinetics and melt orientation. [21] Vleeshouwers and Meijer, [22] and Moitzi and Skalicky, [23] using varying molecular weights, Summary: Polyhydroxybutyrate (PHB) is an ideal bioplastic, however, this polymer undergoes a severe embrittlement process because of its spherulitic structure, rendering the material brittle. Using a series of in-situ rheo techniques, we have previously observed only the rapid initial stage of shish formation, we term a partial shish, which existed at high shears in medium-molecular-weight PHB, M w ¼ 360 000.…”

Section: Introductionmentioning

confidence: 99%

“…This orientation mechanism and its dependency on molecular weight appears to be fundamental to the shish kebab formation. [20][21][22][23][24][25][26][27][28][29][30][31] In this paper, we will explore the relationship between shear flow, molecular weight, and the resultant morphology using ultra-high-molecular-weight (UHMWT) (M w ¼ 5 Â 10 6 ) blended with medium-molecular-weight (MMWT) PHB (M w ¼ 360 000).…”

Section: Introductionmentioning

confidence: 99%

Fiber Formation in Medium and Ultra‐High‐Molecular‐Weight Polyhydroxybutyrate Blends under Shear Flow

Sharma

Ogino

Kanaya

et al. 2004

Macro Materials & Eng

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Summary: Polyhydroxybutyrate (PHB) is an ideal bioplastic, however, this polymer undergoes a severe embrittlement process because of its spherulitic structure, rendering the material brittle. Using a series of in‐situ rheo techniques, we have previously observed only the rapid initial stage of shish formation, we term a partial shish, which existed at high shears in medium‐molecular‐weight PHB, $\overline M _{\rm w}$ = 360 000. The shish kebab morphology is anticipated to remove or severely lessen this embrittlement process whilst providing new properties and applications. For medium and ultra high‐molecular‐weight (MMWT, $\overline M _{\rm w}$ = 360 000/UHMWT, $\overline M _{\rm w}$ = 5 × 106) PHB 99/1 and 99.5/0.5 blends only a partial shish is identified. However, the initial shish formation stage and subsequent stages were observed at 98/2 and 97/3 blend ratios resulting in a complete shish, we term the full shish, and fiber formation was evident. We believe this fiber morphology achieved by high molecular weights is crucial to sustaining the shish kebab structure for an excessive period.

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Simplified model of stress‐induced crystallization kinetics of polymers

Guo

Narh

2002

Adv Polym Technol

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ABSTRACT:A stress-induced crystallization model for semicrystalline plastics is proposed based on the theory that stress-induced orientation of molecules and chains increase the melting temperature of thermoplastics, and hence, the supercooling which is the driving force for crystallization. By assuming that the effect of stress on crystallization is only by increasing the melting temperature, the basic quiescent-state crystallization equation can be directly applied to model stress-induced crystallization kinetics. The model has a minimum of experimentally based constants. A simple experimental technique, such as a rotational rheometer, can be used to determine the melting temperature shift. The model predicts the most prominent features of stress-induced crystallization. The main advantage of the model is that the parameters in the quiescent-state crystallization model do not change. Consequently, the parameters in the melting temperature shift model are easy to determine, and unknown constants are kept to a minimum.

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Shear-induced crystallization of isotactic polypropylene melts: isothermal WAXS experiments with synchrotron radiation

Cited by 70 publications

References 16 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

Fiber Formation in Medium and Ultra‐High‐Molecular‐Weight Polyhydroxybutyrate Blends under Shear Flow

Simplified model of stress‐induced crystallization kinetics of polymers

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