Long‐Chain Branches in Syndiotactic Polypropene Induced by Vinyl Chloride

Stadler, Florian J.; Arikan, Burçak; Kaschta, Joachim; Kaminsky, Werner

doi:10.1002/macp.200900688

Cited by 14 publications

(13 citation statements)

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“…The thermorheological complexity of long-chain branched metallocene PE leads to an increase of the activation energy towards longer relaxation times/lower relaxation strengths [29][30][31]. A similar effect was also found for long-chain branched polypropylenes (PP) and flouropolymers [27,28,32,33]. The base of these methods is to determine the activation energy locally, i.e.…”

Section: Introductionmentioning

confidence: 75%

“…The physical origin of this behavior is totally illusive at the moment, but different from LCB-mPE, because, unlike for LCBmPE, the shape of #(") is not temperature dependent for LDPE [27,28]. Only recently, viable analysis schemes for thermorheological complexity have become available [26,27,[29][30][31][32]. The thermorheological complexity of long-chain branched metallocene PE leads to an increase of the activation energy towards longer relaxation times/lower relaxation strengths [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

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Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Stadler¹

2011

Express Polym. Lett.

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Abstract. Intramolecular phase separation is usually associated with block-copolymers, but the same phenomenon is also obtainable by random-copolymers. In this article, evidence of intramolecular phase separation is reported for a linear octadecene-ethene copolymer, which shows an evolving 'yield point' at a long time and low frequency. This is attributed to a partial phase separation of the long short-chain branches. In creep recovery, this behavior is evident as increasing elastic steady-state creep recovery compliance J e 0 . In contrast to 'normal' block-copolymers, this special polymer has an increase in phase separation with temperature, which is caused by the chemical composition and the short chain segments in the side chain domain, leading to a high surface fraction. Vol.5, No.4 (2011) 327-341 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2011 * Corresponding author, e-mail: fjstadler@jbnu.ac.kr © BME-PT length in their paper, as it cannot be determined due to the synthesis method. Such block-copolymers are usually thermorheologically complex [9,14,15]. The group of Bates [9,10], for example, found that below the order-disorder transition temperature, i.e., in the ordered state, the sample behaves like a gel and thermorheologically simple, while in the disordered state, a clear thermorheological complexity is found. The higher the temperature, the less pronounced the long-term relaxation process and, thus, the more similar is the data to a single-phase polymer melt. Recently, it was also proven that pure ethylene-/!-olefin copolymers with very long comonomers (C26) can be phase separating in the solid state, if their comonomer content is sufficiently high [16]. This effect is different from the previous cases, because it only involves one type of chain and, furthermore, occurs on random copolymers. Hence, it is an effect that occurs only on a short length scale, as shown by the fact that the length of the comonomers used were 18 and 26 carbons. Thus, the second phase has to encompass only the maximum of 24 terminal carbons; realistically, 16-20 carbons. This effect had a small trace in X-ray diffraction, which points to a weak side chain crystallization [17,18]. However, it was shown that the samples showing this phase behavior in the solid state [16] did not show it in the melt state, as the samples behaved like normal linear low density polyethylenes (LLDPEs), being only special because of their higher flow activation energy E a , which is the consequence of the side-chain content s c of the comonomer [19,20]. Phase separation in the melt is usually visible by traces of the interfacial tension [21] and different temperature dependencies of the individual blend components and the interfacial processes [22,23]. Hence, if other techniques don't show any trace, e.g., because of too low differences in the electron density in X-ray scattering, rheological behavior can provide a valuable aid to the characterization of phase separation. Recently, molecular dynamics studies revea...

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Section: Introductionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Stadler¹

2011

Express Polym. Lett.

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“…An example is the study by Stadler and his coworkers. [ 87 ] Trace amounts of VCM were added to the polymerization of propylene catalyzed by [Ph 2 C(2,7-di-tert.BuFlu)(Cp)] ZrCl 2 /MAO to promote the formation of LCBs. The concentration of VCM dramatically decreased the polymer MW, while PDI, crystallinity and syndiotacticity remained the same.…”

Section: Chain Transfer Agentmentioning

confidence: 99%

“…These polymers further serve as macromonomers in the polymerization to form polymers with an enhanced LCB. An example is the study by Stadler and his coworkers . Trace amounts of VCM were added to the polymerization of propylene catalyzed by [Ph 2 C(2,7‐di‐tert.BuFlu)(Cp)]ZrCl 2 /MAO to promote the formation of LCBs.…”

Section: Metallocene Catalystsmentioning

confidence: 99%

A Comprehensive Review on Controlled Synthesis of Long-Chain Branched Polyolefins: Part 1, Single Catalyst Systems

Liu

Wang

et al. 2016

Macromol. React. Eng.

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Polyolefins (POs) are the largest polymer product in the world. The innovation in converting commodity olefin monomers to highly value added high‐performance POs has been and will continue to be a major theme in both academic research and industry practice. The excellent properties of POs can be achieved through precise engineering of their chain architectures, which largely involves control of the chain branching structures. Long‐chain branching is one of the most important parameters in the aspect of various chain branching structures. A huge amount of literatures have been reported to achieve better control of long‐chain branched structures over the last two decades. Recently, good effort has been made in reviewing all the major literatures and summarizing the catalytic systems and synthetic strategies for the controlled synthesis of long‐chain branched POs. This paper represents the first of the series, that is, controlled synthesis of long‐chain branched POs via single catalyst systems.

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“…angular frequency ω varies, which leads to a non-constant Ea and, thus, to thermorheological complexity, as the shape of the rheological functions varies due to the temperature dependence of the shape of the relaxation (or retardation) spectrum [22]. Thermorheological complexity was previously found for long-chain branched polyethylene (discussed below), polypropylene [23][24][25][26], hydrogenated polybutadiene [18,21], fluoro-polymers [27], and polylactides [28]. The authors are not aware of any reliable publications, where long-chain branching in Arrhenius-type materials does not lead to an increase in Ea and to thermorheological complexity.…”

Section: Introductionmentioning

confidence: 99%

Rheological Behavior of Blends of Metallocene Catalyzed Long-Chain Branched Polyethylenes. Part I: Shear Rheological and Thermorheological Behavior

Chen¹,

Shekh²,

Cui³

et al. 2021

Preprint

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Long-chain branched metallocene-catalyzed high-density polyethylenes (LCB-mHDPE) were solution blended to obtain blends with varying degrees of branching. A high molecular LCB-mHDPE was mixed with low molecular LCB-mHDPE are varying concentrations, whose rheological behavior is similar but whose molar mass and molar mass distribution is significantly different. Those blends were characterized rheologically to study the effects of concentration, molar mass distribution, and long-chain branching level of the low molecular LCB-mHDPE. Owing to the ultra-long relaxation times of the high molecular LCB-mHDPE, the blends started behaving clearly more long-chain branched than the base materials. The thermorheological complexity showed an apparent increase in the activation energies Ea determined from G’, G”, and especially δ. Ea(δ), which for LCB-mHDPE is a peak function, turned out to produce even more pronounced peaks than observed for regular LCB-mPE and also LCB-mPE with broader molar mass distribution. Thus, it is possible to estimate the molar mass distribution from the details of the thermorheological complexity.

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Long‐Chain Branches in Syndiotactic Polypropene Induced by Vinyl Chloride

Cited by 14 publications

References 80 publications

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

A Comprehensive Review on Controlled Synthesis of Long-Chain Branched Polyolefins: Part 1, Single Catalyst Systems

Rheological Behavior of Blends of Metallocene Catalyzed Long-Chain Branched Polyethylenes. Part I: Shear Rheological and Thermorheological Behavior

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