Influence of chalk and its surface treatment on crystallization of filled polypropylene

Kowalewski, Tomasz; Gałęski, Andrzej

doi:10.1002/app.1986.070320107

Cited by 87 publications

(39 citation statements)

References 11 publications

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“…However, it is generally assumed that non-integral values of n are caused by factors such as secondary crystallization and mixed nucleation modes, rather than being a genuine reflection of non-three dimensional development. Under these circumstances, Kowalewski and Galeski (32) suggested that the effective 3-dimensional crystallization rate constant, K 3 , can be determined from the experimentally measured K exp using the relationship: -( ) (2) where N represents the number of nucleation sites per unit volume and G is the growth rate of the crystallizing objects. The value of this approach is that heterogeneous nucleation is closely related to the local interactions that occur between the crystallizing polymer and the substrate -the difference energy parameter in the theory of Muchová and Lednický (35) .…”

Section: Crystallization Behaviourmentioning

confidence: 99%

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: Crystallization Behaviourmentioning

confidence: 99%

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

2006

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“…Assuming that the nucleation occurs instantaneously, and taking into account the dimensions of the spherulites are proportional to the C3-content in EPR. approximation of Kowalewski and Galeski, 22 the density of the crystallization nuclei, N, is given by the following equation:…”

Section: Introductionmentioning

confidence: 99%

Crystallization and morphology of reactor-made blends of isotactic polypropylene and ethylene-propylene rubber

Yokoyama

Riccò

1997

J. Appl. Polym. Sci.

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ABSTRACT:The crystallization and morphology of reactor-made blends of isotactic polypropylene ( PP ) with a large content of ethylene -propylene rubber ( EPR ) (i.e., ú 50%) were investigated. In the blends, PP was found to form spherulites during the crystallization process, with the growth rate constant under isothermal conditions. For crystallization temperatures in the range of 118 -152ЊC, the birefringence of the spherulites varied from negative to positive by decreasing crystallization temperature, while homopolypropylene ( homo-PP ) , the same as used in the blends as a matrix, showed negative spherulites in the whole temperature range investigated ( 118 -152ЊC ) . Both the spherulite growth rate and the overall crystallization rate were slower for the blends than for homo-PP. The density of the crystallization nuclei was lower in the blends than in the homo-PP. It was concluded that a large amount of EPR content in the reactor-made blends of PP retards and hinders the crystallization of the matrix.

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“…A similar finding was reported earlier: CaCO 3 acted as a nucleating agent in the crystallization of PP, and this effect was more pronounced with untreated CaCO 3 than a stearic acid coated type. 25,26 The percentage of crystallinity observed in the filled composites is lower than that of unfilled PP, and this can be explained by the substitution of PP by the rigid filler. To compare the crystallinity of only the crystallizable component in each sample, the percentage of crystallinity per unit weight of the crystallizable component was calculated and reported as a percentage of the normalized crystallinity.…”

Section: Resultsmentioning

confidence: 92%

Crosslinkable polypropylene composites made by the introduction of silane moieties

Sirisinha

Kawko

2005

J of Applied Polymer Sci

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Silane-crosslinkable polypropylene (PP) composites containing calcium carbonate (CaCO 3 ) as a filler have been investigated. The melt grafting of vinyl trimethoxysilane to PP with dicumyl peroxide (DCP) as a radical initiator is demonstrated. The thermal and mechanical properties of the crosslinkable products are also discussed. The results show that two reactions, that is, silane grafting and PP degradation, take place in parallel. The extents of silane grafting and PP degradation strongly depend on the reaction temperature, grafting formulation, and amount of the filler in the systems. Increasing the DCP concentration (up to 0.05 wt %) leads to an increase in the grafting degree. However, when the concentration of radicals is over a certain degree, the dominant reaction is PP chain scission. This results in a drastic decrease in the polymer viscosity. In systems containing both silane and CaCO 3 , the viscosity of the polymer is higher than that of a grafted sample without CaCO 3 addition; in other words, the effect of the filler on the polymer viscosity compensates for the effect caused by PP degradation. Differential scanning calorimetry results show that the crystallization starts earlier for grafted samples. The percentage of the crystallinity of grafted PP is higher than that of the pure polymer. The incorporated silane does not have a strong effect on the mobility of the PP chains, as revealed by dynamic mechanical analysis. In comparison with ungrafted composites, the silane-crosslinkable products show higher tensile stress and modulus.

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Influence of chalk and its surface treatment on crystallization of filled polypropylene

Cited by 87 publications

References 11 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

Crystallization and morphology of reactor-made blends of isotactic polypropylene and ethylene-propylene rubber

Crosslinkable polypropylene composites made by the introduction of silane moieties

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