Thermal and morphological evaluation of very low density polyethylene/high density polyethylene blends

Arnal, María L.; Cañizales, Edgar; Müller, Alejandro J.

doi:10.1002/pen.11096

Cited by 26 publications

(32 citation statements)

References 34 publications

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“…The only difference existed in the lower T m and T c values in comparison with those of set A, which are clearly displayed in Table I. Such phenomena were discovered and explained clearly for similar systems in earlier reports 5,[41][42][43][44][45] and were predominantly due to the different increased contents of HBPE in the mixtures. Figure 7 presents the relationship between the weight content of HBPE in the blends (W tHBPE ) and X C .…”

Section: Microstructural Characterizationsupporting

confidence: 53%

Influence of branching on the thermal and crystallization behavior of bimodal polyethylenes synthesized with binary late‐transition‐metal catalyst combinations

Long

Liu

Cui

et al. 2009

J of Applied Polymer Sci

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Two reactor blends of linear and branched polyethylene resins with bimodal molecular weight distributions were synthesized in a one-reactor polymerization process through the combination of 2,6-bis[1-(2,6-dimethyphenylimino)pyridyl]cobalt dichloride (1) and 2,3-bis(2,6-diisopropylphenyl)butanediimine nickel dibromide (2) or 1,2-bis(2,6-diisopropylphenyl)cyclohexene diimine nickel dibromide (3) in the presence of modified methylaluminoxane. The linear correlation between the catalyst activity and concentration of the nickel compounds suggested that the catalysts performed independently of one another. The molecular weights, molecular weight distributions, and crystalline and phase structures of the blends were investigated with a combination of high-temperature gel permeation chromatography, differential scanning calorimetry, wideangle X-ray diffraction, and small-angle X-ray scattering techniques. The branching degree of the polyethylene produced with 3 was much higher than the branching degree of the sample produced with 2, although their molecular weights were relatively close. In addition, the crystallization rate, melting temperature, degree of crystallinity, and crystallization temperature of more highly branched blends produced with 1/3 were lower. The long periods and thickness of the crystalline region were greatly influenced by the addition of highly branched polyethylene.

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Section: Microstructural Characterizationsupporting

confidence: 53%

Influence of branching on the thermal and crystallization behavior of bimodal polyethylenes synthesized with binary late‐transition‐metal catalyst combinations

Long

Liu

Cui

et al. 2009

J of Applied Polymer Sci

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“…This probably indicates that most linear chain fractions within PEB are co-crystallizing in the blends with some PEH chain fractions. [22][23][24] The presence of fractions with similar SCB contents is demonstrated in Figure 1b and explained above. For compositions with PEB contents of 40% or less, the PEB rich phase was very difficult to detect and therefore no values of T cII are reported in Table 1.…”

Section: Standard Dsc Scansmentioning

confidence: 87%

“…In this case, co-crystallization between chains of similar SCB contents can occur as previously reported in similar blends. [23][24][25] The crystallization kinetics results demonstrate that there is a strong competition between phase segregation and crystallization which is temperature dependent. Upon cooling from a one phase melt, phase segregation precedes crystallization if the crystallization temperature (T c ) is high.…”

Section: Discussionmentioning

confidence: 99%

“…This corroborates the results obtained in Figure 4a and Table 1 which indicate the possible co-crystallization of PEB and PEH fractions. [22][23][24] In order to explore the possible effects of phase segregation in the melt with minimum interference from segregation during crystallization, the samples were quickly quenched from an initial melt temperature (either ''treatment A'' or ''treatment B'') into acetone at À5 8C. Following this treatment, the DSC heating scans presented in Figure 5 were recorded at 10 8C Á min À1 .…”

Section: Standard Dsc Scansmentioning

confidence: 99%

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Morphology and Crystallization Kinetics of Melt Miscible Polyolefin Blends

Müller

Arnal

Spinelli

et al. 2003

Macro Chemistry & Physics

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Blends of copolymers of ethylene/hexene (9 CH3/1 000 C) and ethylene/butene (77 CH3/1 000 C) synthesized with metallocene catalysts were prepared by co‐precipitation from solution. A phase diagram for this blend had been obtained in a preceding work, where the blends were found to be miscible in the melt with a characteristic upper critical solution temperature (UCST). In this work, the successive self‐nucleation and annealing (SSA) thermal fractionation method revealed that both pure copolymers, even though they had been prepared by metallocene catalysis, displayed a very broad distribution of short chain branching. The thermal behavior of the pure copolymers and their blends revealed that co‐crystallization effects were present within each phase and that molecular fractionation during crystallization can prevail when the materials are slow cooled from the melt. A crystallization kinetics study was performed by differential scanning calorimetry (DSC) and it revealed a strong competition between crystallization and phase segregation. Upon cooling from a one phase melt, phase segregation precedes crystallization if the crystallization temperature (Tc) is high. On the other hand when low crystallization temperatures are employed, the amount of phase segregation that can be achieved before crystallization is limited. Transmission electron microscopy (TEM) allowed the observation of the lamellar morphology and their aggregation state. In specially prepared samples, the relative lamellar frequency of isothermally crystallized material was employed to ascertain whether the blend under consideration was within the one or the two phase region of the blends phase diagram.Crystallization half‐time for isothermally crystallized PEB/PEH blends quenched to the crystallization temperature from 170 °C.magnified imageCrystallization half‐time for isothermally crystallized PEB/PEH blends quenched to the crystallization temperature from 170 °C.

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“…[4][5][6] It should be expected that the properties of blends of high density polyethylene (HDPE) and ethylene copolymers, with not very high content of the comonomer, will mostly depend on crystallinity, morphology and degree of dispersion, but on the contrary the properties seem to be considerably affected by the polymer miscibility in the molten state. [4,[7][8][9][10] Therefore the investigations on the kinetics of polymer crystallization are significant in both…”

Section: Introductionmentioning

confidence: 99%

Study on the Phase Behavior of High Density Polyethylene – Ethylene Octene Copolymer Blends

Mileva

Radusch

Betchev

2007

Macro Materials & Eng

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The processes of melting and crystallization of blends based on HDPE and EOC were investigated. DSC thermograms showed that a separate crystallization and co‐crystallization occurred in the blends studied. Avrami approach was used to analyze the kinetics of crystallization in the blends. It is shown that the Avrami exponent depends on the EOC concentration of the samples studied. The difference in the Avrami parameters for HDPE, EOC and the blends indicated that the nucleation mechanism and dimension of the spherulite growth of the blends were different from that of HDPE to some extent. The crystal growth was examined in the context of the Lauritzen‐Hoffman theory. DSC traces obtained at different cooling rates were used for analyzing the non‐isothermal crystallization. It was found that the Ozawa model was rather inapplicable for the materials studied. In contrast, the Avrami equation modified by Jeziorny can be used more efficiently to describe the non‐isothermal crystallization behavior of HDPE‐EOC blends.magnified image

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Thermal and morphological evaluation of very low density polyethylene/high density polyethylene blends

Cited by 26 publications

References 34 publications

Influence of branching on the thermal and crystallization behavior of bimodal polyethylenes synthesized with binary late‐transition‐metal catalyst combinations

Influence of branching on the thermal and crystallization behavior of bimodal polyethylenes synthesized with binary late‐transition‐metal catalyst combinations

Morphology and Crystallization Kinetics of Melt Miscible Polyolefin Blends

Study on the Phase Behavior of High Density Polyethylene – Ethylene Octene Copolymer Blends

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