Real time in situ X-ray diffraction studies on the melting memory effect in the crystallization of β-isotactic polypropylene

Cho, Kangwoo; Saheb, D. Nabi; Choi, Jaeseung; Yang, Hoichang

doi:10.1016/s0032-3861(01)00729-7

Cited by 113 publications

(77 citation statements)

References 28 publications

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“…The appearance of the different crystalline forms depends to a large extend on the chain microstructure, [20,21] processing conditions [22,23] and presence of specific nucleating agents. [24,25] However, under C. Hedesiu et al conditions as usually applied during industrial processing the a-form is always predominant.…”

Section: X-ray Resultsmentioning

confidence: 99%

Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

Hedesiu

Demco

Kleppinger

et al. 2008

Macro Materials & Eng

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Changes in phase composition and chain mobility in injection‐molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time‐domain 1H solid‐state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection‐molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi‐rigid and amorphous fractions.

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Section: X-ray Resultsmentioning

confidence: 99%

Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

Hedesiu

Demco

Kleppinger

et al. 2008

Macro Materials & Eng

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“…This unique behavior was present only in the copolymers; the linear PE studied by Reid et al showed the expected behavior; that is, for any temperature above T 0 m the melt was always homogeneous and no evidence of self nucleation was reported (see Fig. 19) [4,20,31,69,124,125].…”

Section: Influence Of Confinement On Self-nucleation Behaviormentioning

confidence: 88%

“…It should be noted that the poly(ethylenealt-propylene) (PEP) block cannot crystallize. This copolymer was synthesized via hydrogenation of the B 24 EP 56 EO 20 67 precursor employing the Wilkinson catalyst. Wilkinson catalysis provides active heterogeneities to the PEO block.…”

Section: Influence Of Confinement On Self-nucleation Behaviormentioning

confidence: 99%

“…17, where a direct transition from domain I to III can be observed [98]. 20 Pérez et al [119] studied the crystallization of linear (L-PCL) and cyclic (C-PCL) PCL chains of almost identical molecular weights. They found that the transition temperatures between domains are affected by chain topology (see Table 1).…”

Section: Influence Of Confinement On Self-nucleation Behaviormentioning

confidence: 99%

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Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Michell

Múgica

Zubitur

et al. 2015

Advances in Polymer Science

126

303

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Self-nucleation (SN) is a special nucleation process triggered by selfseeds or self-nuclei that are generated in a given polymeric material by specific thermal protocols or by inducing chain orientation in the molten or partially molten state. SN increases the nucleation density of polymers by several orders of magnitude, producing significant modifications to their morphology and overall crystallization kinetics. In fact, SN can be used as a tool for investigating the overall isothermal crystallization kinetics of slow-crystallizing materials by accelerating the primary nucleation stage in a previous SN step. Additionally, SN can facilitate the formation of one particular crystalline phase in polymorphic materials. The SN behavior of a given polymer is influenced by its molecular weight, molecular topology, and chemical structure, among other intrinsic and extrinsic characteristics. This review paper focuses on the applications of DSC-based SN techniques to study the nucleation, crystallization, and morphology of different types of polymers, blends, copolymers, and nanocomposites.

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“…Such a ''memory'' or ''self-nucleation effect'' is well known, [11][12][13][14] but is rarely employed for the X-ray investigation of anisotropic, quiescent crystallization. Nevertheless, the information content of the resulting scattering patterns is much higher than that from isotropic materials.…”

Section: Introductionmentioning

confidence: 99%

Oriented Quiescent Crystallization of Polyethylene Studied by USAXS

Stribeck

Camarillo

Cunis

et al. 2004

Macro Chemistry & Physics

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Summary: Highly oriented high‐pressure injection‐molded (HPIM) rods from polyethylene (PE) were heated until the discrete small‐angle X‐ray scattering (SAXS) had vanished. Thereafter, non‐isothermal and isothermal crystallization was investigated in situ by means of ultra small‐angle X‐ray scattering (USAXS). The orientation of the crystallites could be controlled by choice of the melt annealing temperature (shish‐kebab model: memory or self‐nucleation effect caused by stable shishs). Both the scattering patterns and the multidimensional chord distribution function (CDF) were interpreted. A three‐stage model of crystallization was also developed. This model comprises row structure nucleation, the almost statistical insertion of extended lamellae and finally the insertion of blocky crystallites. It was found that the nanostructure evolution in the isotropic fraction of the material was the same as in the highly oriented one. The lateral extension of the lamellae was largest during isothermal crystallization. The correlation among domains was increased by non‐isothermal crystallization. The shishs in the core of the HPIM rod appeared less stable than those in the shell. Lobe‐shaped reflections observed during and after quenching were not due to an orientation distribution of layer stacks, but reflected a correlation between long period and lateral extension of crystallites. During quenching, a lateral modulation of the layer peaks in the CDF grew stronger and showed the arrangement of block‐shaped crystals proposed by Strobl to be the precursors of lamellae. The thin crystals formed during rapid cooling were built from a central block surrounded by one or two rings of satellites. The long period observed in the scattering pattern during quenching is due to correlations among crystalline blocks in a chain, and not from correlations among lamellae.USAXS scattering patterns from isothermal, oriented crystallization of HPIM‐PE material (bottom row: during final quenching after 30 min at 127 °C).magnified imageUSAXS scattering patterns from isothermal, oriented crystallization of HPIM‐PE material (bottom row: during final quenching after 30 min at 127 °C).

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Real time in situ X-ray diffraction studies on the melting memory effect in the crystallization of β-isotactic polypropylene

Cited by 113 publications

References 28 publications

Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

Aging Effects on the Phase Composition and Chain Mobility of Isotactic Poly(propylene)

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Oriented Quiescent Crystallization of Polyethylene Studied by USAXS

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