Spherulite nucleation in isotactic polypropylene based nanocomposites with montmorillonite under shear

Nowacki, R.; Monasse, Bernard; Piórkowska, Ewa; Gałęski, Andrzej; Haudin, Jean‐Marc

doi:10.1016/j.polymer.2004.04.058

Cited by 94 publications

(82 citation statements)

References 31 publications

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“…As shown at a lower magnification in Fig. 8, it is apparent that with this processing route, extremely large clay aggregates exist within this material, which exceed the quoted size range for Nanocor I30P (17) . Nevertheless, Figs.…”

Section: Materials Microstructurementioning

confidence: 70%

“…Two MMT systems were examined, the octadecyl ammonium-modified montmorillonite I30P (Nanocor) (17) and the polyethylene/MMT master batch (MB) C30PE (Nanocor); C30PE contains approximately 50% MMT and 50% polyethylene. Five specimen formulations, designated A to E were prepared using either solution blending in xylene, or melt mixing in a Randcastle RCP-0375 microtruder that incorporates a recirculating * ECS, University of Southampton Highfield, Southampton SO17 1BJ, UK Paper mixing section to promote dispersion -see Table 1.…”

Section: Methodsmentioning

confidence: 99%

“…9. Low magnification SEM image of Material E; Sizable aggregates of MMT can still be readily seen as bright inclusions; the structure of the matrix polymer is, however, unclear; Scale bar: 80 µm nucleant (17) (35) (36) . However, in comparison with other highly nucleated polymers, the degree of nucleation enhancement implied by Fig.…”

Section: Crystallization Behaviourmentioning

confidence: 99%

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Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

2006

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Polymeric composites containing nanometric fillers have attracted considerable interest because of the attractive properties that such materials can display. In the area of nanodielectrics, many workers have stressed the significance of the interfaces that exist between such fillers and the host polymer as being critical in influencing properties. Indeed, Tanaka (1) proposed a concentric shell model in which interactions can be thought of as occurring at a range of dimensional levels; Nelson and Fothergill (2) considered nanodielectrics in terms of an interaction zone. In this work, we set out to prepare a range of nanocomposites based on polyethylene (PE) and montmorillonite nanoclay (MMT), to examine the effect of MMT dispersion on properties and structure formation and, thereby, to explore both short-range molecular effects and the extent of the polymer/nanoclay interaction zone. Figure 1 compares AC ramp breakdown results obtained from 3 materials at a ramp rate of 50 V s -1 . Where dispersion of the MMT is poor (C Quenched), the breakdown strength is greatly reduced compared with a comparable system containing well-dispersed nanoclay (E Quenched). This is in line with behaviour reported for nano-and microcomposites (2) , suggesting that it is attributable to aggregation of the MMT in C. However, attempts to improve the breakdown strength of E by controlled crystallization were unsuccessful; systems prepared by rapid quenching from the melt or by prolonged isothermal crystallization both behaved in an equivalent manner. This is in contrast to the same polymer, but without MMT (B 117 o C), where controlled crystallization can lead to improved properties, as reported elsewhere (3) . Thus, when quenched, equivalent polyethylene materials with and without MMT exhibit similar breakdown behaviour, provided the MMT is well dispersed. However, in the absence of MMT, isothermal crystallization can result in improved performance whereas, when MMT is present, this appears not to occur.To explore the origin of the above effects, the influence of MMT on structural evolution in PE was examined. In the scanning electron microscope (SEM), all the materials where MMT was absent or poorly dispersed were found to exhibit spherulitic morphologies. In contrast, Fig.2 shows a sample of Material E, which contains 5% by weight MMT, following crystallization at 117 o C. An MMT aggregate ~1 µm in size can be seen near the centre of this image but, elsewhere, it is not possible to distinguish MMT platelets from polymer lamellae. Although the material is highly nucleated, the lamellar texture also appears highly disrupted. Thus, in the absence of MMT or when the MMT is poorly dispersed, crystallization of the polymer leads to conventional morphologies, whereas well-dispersed MMT appears to promote nucleation but, subsequently, to disrupt the processes by which ordered structures form. This interpretation of fig.2 is supported by quantitative studies of crystallization kinetics and the thermodynamics of crystallization. MMT increases...

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Section: Materials Microstructurementioning

confidence: 70%

Section: Methodsmentioning

confidence: 99%

Section: Crystallization Behaviourmentioning

confidence: 99%

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Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

2006

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“…the radial distribution of shear rate. The strong spherulite nucleation on surface adhering to the glass was observed [8], giving place to a thin layer with dimension of the order of the spherulite radii observed in corresponding core. It is concluded then that the number of spherulites determined in really thin films crystallized in contact with a glass support could be not representative for bulk.…”

Section: Resultsmentioning

confidence: 92%

Spherulitic nucleation and growth rates in a sheared polypropylene melt

Santis¹,

Scermino²,

Pantani³

et al. 2014

AIP Conference Proceedings

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In common polymer processing operations such as injection molding, film blowing, and fiber spinning, the molten polymer is subjected to intense shear and/or elongational flow fields and crystallizes during or after the application of flow. The semicrystalline morphology that develops in the final product is typically very different from what is observed during quiescent crystallization of the same polymer, and the properties change accordingly. The possibility of controlling the final morphology and the resulting mechanical and functional properties of semicrystalline polymers based on the study of polymer melt crystallization stimulated by flow is highly intriguing. This work starts from the experimental evidence that there exists qualitatively three regimes of crystallization under shear: (a) very low shear rates, in which there is no effect on kinetics; (b) higher shear rates, in which orientational effects enhance just the nucleation and growth rates, and spherulitic crystallization is observed; and (c) high shear rates, in which molecular stretching occurs giving rise to a fibrillar morphology development under very fast kinetics. The first two regimes are explored and analyzed by means of experimental protocols developed on purpose. In particular: -spherulitic nucleation and growth rates under continuous shear rates were carefully measured and related to molecular strain -the condition below which crystallization turns out to be essentially quiescent was evidenced.

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“…5) [64]. The resulting crystal structure of PP in this type of fiber/PP composites exhibits lower lamellae thickness but is less disposed to recrystallization and is more stable [65][66][67] Recently, much attention has been paid to PP-nanocomposites, produced by different techniques and containing mainly carbon nanotubes/nanofibers or layered silicates [68][69][70][71][72][73][74][75][76][77][78][79]. Numerous reports describe the fabrication of a range of PP-nanocomposites, and, in particular, the impact of nanofillers on the crystallization of a matrix.…”

Section: Nucleation and Its Experimental Evaluationmentioning

confidence: 99%

Crystallization of Polypropylene: Application of Differential Scanning Calorimetry Part Ii. Crystal Forms and Nucleation

Raka¹,

Bogoeva‐Gaceva²

2017

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Spherulite nucleation in isotactic polypropylene based nanocomposites with montmorillonite under shear

Cited by 94 publications

References 31 publications

Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

Polyethylene Nanodielectrics: The Influence of Nanoclays on Structure Formation and Dielectric Breakdown

Spherulitic nucleation and growth rates in a sheared polypropylene melt

Crystallization of Polypropylene: Application of Differential Scanning Calorimetry Part Ii. Crystal Forms and Nucleation

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