Molecular Weight Distribution of Ethylene/1‐Olefin Copolymers: Generalized Bimodality Criterion

Vichitlimaporn, Charut; Anantawaraskul, Siripon; Soares, João B. P.

doi:10.1002/mats.201600060

Cited by 4 publications

(3 citation statements)

References 27 publications

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“…The general kinetic scheme proposed by G. Natta [39] for the propylene polymerization over Ziegler-Natta catalysts (Scheme 1) is usually used for the kinetic analysis of catalytic polymerization of olefins. This scheme has been discussed in many papers [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53].…”

Section: Resultsmentioning

confidence: 99%

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts

Matsko,

Zakharov

2023

Polymers

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In this review, we summarize and discuss our experimental data published in a number of papers on the transfer reactions of polymer chains in the polymerization of ethylene, propylene, and hexene-1, and the copolymerization of ethylene with α-olefins over multisite supported titanium–magnesium catalysts (TMC). Three groups of transfer reactions are discussed in the review: (1) transfer reactions with AlEt3 cocatalyst, (2) transfer reactions with hydrogen, and (3) transfer reactions with participation of α-olefins in the case of ethylene copolymerization with α-olefins. We have found polymerization conditions where it is possible to observe heterogeneity of active sites of TMC for all three groups of the indicated reactions. It is shown that (1) the transfer reaction with AlEt3 proceeds with higher reactivity on the active sites that produce polymers with low molecular weight; (2) the transfer reaction with hydrogen, in the case of α-olefin polymerization and copolymerization of ethylene with α-olefins, proceeds with higher reactivity on the active sites which produce polymers with high molecular weight; (3) the transfer reaction with α-olefins proceed with higher reactivity on the active sites that produce high molecular weight polymers.

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Section: Resultsmentioning

confidence: 99%

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts

Matsko,

Zakharov

2023

Polymers

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“…Highly specialized tests are much more accurate than the more general ones; however, they should only be used for the specific distributions they are specialized for. For example, Vichitlimaporn et al [15] present highly specialized bimodality criterions for the molecular weight distributions in copolymers. Hassanian-Moghaddam et al [16] present a similar criterion for the bivariate distribution of chain length and chemical composition of copolymers.…”

Section: Introductionmentioning

confidence: 99%

On Generalizing Sarle’s Bimodality Coefficient as a Path towards a Newly Composite Bimodality Coefficient

2022

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Determining whether a distribution is bimodal is of great interest for many applications. Several tests have been developed, but the only ones that can be run extremely fast, in constant time on any variable-size signal window, are based on Sarle’s bimodality coefficient. We propose in this paper a generalization of this coefficient, to prove its validity, and show how each coefficient can be computed in a fast manner, in constant time, for random regions pertaining to a large dataset. We present some of the caveats of these coefficients and potential ways to circumvent them. We also propose a composite bimodality coefficient obtained as a product of the weighted generalized coefficients. We determine the potential best set of weights to associate with our composite coefficient when using up to three generalized coefficients. Finally, we prove that the composite coefficient outperforms any individual generalized coefficient.

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“…Microstructural distributions of polyethylene can be tailor‐made by selection of polymerization system, operating conditions, and catalyst types. [ 1–10 ] Molecular weight distribution (MWD) and chemical composition distribution (CCD) are two of the critical microstructural distributions influencing final properties. [ 11–14 ] These distributions of polyethylene produced by metallocene catalyst (i.e., single‐site type catalyst) are relatively narrow compared to those produced by Ziegler–Natta catalyst (i.e., multiple‐site type catalyst), which is commonly used in industry.…”

Section: Introductionmentioning

confidence: 99%

Cocrystallization of Polyethylene Blends during TREF–GPC Cross‐Fractionation Characterization

Piriyakulkit

Kanoknukulchai

Potisatityuenyong

et al. 2022

Macro Chemistry & Physics

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Cross-fractionation characterization (CFC) between temperature rising elution fractionation (TREF) and gel permeation chromatography (GPC) isa technique developed to determine the bivariate molecular weight and chemical composition distribution (MWDxCCD), a unique and detailed microstructural fingerprint of polyolefin. Like other crystallization-based characterization techniques, CFC may suffer from cocrystallization effects during analysis, which can mislead the interpretation of polymer microstructures. However, cocrystallization phenomena during CFC analysis are not investigated, especially for industrial polymers. In this study, the cocrystallization effect during CFC analysis is systematically investigated using two series of binary blends based on four individual polyethylene samples. These individual samples have distinct microstructural characteristics, representing polyethylene produced using different polymerization processes and catalytic systems. The effects of microstructural characteristics and blending ratio on cocrystallization level are examined. When the CFC profiles of individual components do not overlap, a high level of cocrystallization can be observed. Furthermore, the behavior of how the blending ratio affects cocrystallization depends on the characteristics of CFC profiles of individual component and their interactions. The level of cocrystallization in binary blends increases with the weight fraction of the component having microstructures eluted in the cocrystallization temperature range.

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Molecular Weight Distribution of Ethylene/1‐Olefin Copolymers: Generalized Bimodality Criterion

Cited by 4 publications

References 27 publications

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts

On Generalizing Sarle’s Bimodality Coefficient as a Path towards a Newly Composite Bimodality Coefficient

Cocrystallization of Polyethylene Blends during TREF–GPC Cross‐Fractionation Characterization

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