Detection of Low Levels of Long-Chain Branching in Polyolefins

Karjala, Thomas W.; Sammler, Robert L.; Mangnus, Marc; Hazlitt, Lonnie G.; Johnson, M. D.; Hagen, Charles M.; Huang, J. W. L.; Reichek, K. N.

doi:10.1063/1.2964685

Cited by 7 publications

(7 citation statements)

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“…Loss angle ( δ ) for LCB polymers is significantly different from the linear chains because polymers with LCB exhibit the gel‐like rheological behaviour and the δ values are independent upon the sweep frequency in a limited frequency range. In addition, the plateau region of δ becomes more apparent and the δ value decreases with the LCB level increasing.…”

Section: Resultsmentioning

confidence: 99%

Influence of polypropylene topological structure evolution during melt branching reactive processing on its melt performances

Yang

Jiang

Gong

et al. 2018

Polymers for Advanced Techs

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Gel-free long-chain-branched polypropylene (LCBPP) was prepared by the melt radical branching reaction in the presence of peroxide initiator 2,5-dimethyl-2,5-di(tertbutylperoxy) hexane peroxide, zinc dimethyldithiocarbamate, and trimethylolpropane triacrylate in a torque rheometer. It could be inferred that recombination between PP chains via radical coupled reaction took place and trimethylolpropane triacrylate was grafted onto PP backbone by the torque curves and Fourier transformed infrared spectroscopy results. The presence of long chain branches (LCB) for modified PP was verified by the gel permeation chromatography measurements and vGP plots. On the other hand, it was found that the topological structure of PP chains transformed from linear form to a long star-like shape during the reaction progress, and the topological structure was directly determined by the radical reaction time. The topological structure of PP would further impact its melt behaviour. After complete melting of raw PP, "sparse and long" LCBPP firstly generated which possessed high melt strength owing to the increasing entanglement of long branching chains. And at the time corresponding to the summit of reaction peak on the torque curve, the modified LCBPP possess the highest melt strength owing to its long star topological structure. While as reaction time was prolonged, severe degradation of the LCBPPs would take place under too long mixing time and "dense and short" branches generated due to the residual radicals, with a sharp decline in melt strength. KEYWORDS long chain branched (LCB), melt performance, polypropylene (PP), rheology, topological structure 1 | INTRODUCTION Isotactic polypropylene is one of the most widely used resins owing to its desirable and beneficial advantages such as low density, high melting point, wide sources, superior mechanical properties, and chemical stability. 1,2 However, ordinary commercial polypropylene, prepared by Ziegler-Natta or metallocene catalyst, cannot be applied into some processes where entanglement properties and melt strength are dominant, such as thermoforming, extrusion foaming, and blow molding, due to its linear structure and poor melt strength. Therefore, it is essential to improve the melt strength of PP. It was reported that fraction of long-chain-branched (LCB) or crosslinked structures in PP were able to enhance the melt strength remarkably owing to the augment of the entanglements among the macromolecule chains. 3 When LCB exists, PP can obviously exhibit strain hardening behaviour in the melt state. 4,5As a simple and effective way, melt radical addition is mostly applied to fabricate long-chain-branched polypropylene (LCBPP) recently. [5][6][7] Compared with in situ polymerization in a reactor and high-energy electron irradiation method, melt radical reaction has some unique advantages such as solvent-free process, short reactive time, and low cost. Nonetheless, the preparation technology and

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Section: Resultsmentioning

confidence: 99%

Influence of polypropylene topological structure evolution during melt branching reactive processing on its melt performances

Yang

Jiang

Gong

et al. 2018

Polymers for Advanced Techs

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“…20 In this part, the relationships between rheology LCBi and the LCB measurement from 3D-GPC, that is, gpcBR, LCBf (IV), and LCBf (LS) were illustrated. 20 In this part, the relationships between rheology LCBi and the LCB measurement from 3D-GPC, that is, gpcBR, LCBf (IV), and LCBf (LS) were illustrated.…”

Section: 65mentioning

confidence: 99%

“…. 20 In this part, the relationships between rheology LCBi and the LCB measurement from 3D-GPC, that is, gpcBR, LCBf (IV), and LCBf (LS) were illustrated. This test was done on the same set of LDPE samples used in "Polymer structure property relationship-relationship of LCB and processing properties" below for the coating neck-in test.…”

Section: 65mentioning

confidence: 99%

Methods of long chain branching detection in PE by triple‐detector gel permeation chromatography

Pathaweeisariyakul

Narkchamnan

Thitisuk

et al. 2015

J of Applied Polymer Sci

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Long chain branching (LCB) in polyethylene is one of the key microstructures that controls processing and final properties. Gel permeation chromatography (GPC) with viscometer (IV) and/or light scattering (LS) has been intensely used to quantify LCB. The widespread method to quantify LCB from GPC with IV or LS is the method of LCB frequency (LCBf) based on the Zimm-Stockmayer (ZS) random branching model. In this work, the conventional approach was compared with the recently developed method, called gpcBR. The comparison of the sensitivity of both methods is made on highly branched polymer, that is, various grades of commercial LDPE and also on polymer with very low level of LCB, that is, a commercial HDPE with no LCB, converted into several branched test samples of gradually increasing LCB by multiple extrusion. Finally, the linkages of LCB quantities from both methods to the rheological data and processing properties are illustrated. The new gpcBR index can access lower LCB level and shows obviously better relationship with both rheological data and processing properties than LCBf from the conventional ZS model.

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“…Additionally, and out of the scope of this article, we find that conventional GPC data are also preferred, relative to LALLS data, 31 to interpret low LCB levels in ethylene a-olefin copolymers. 37 The advantage of the conventional GPC method is that it is dominated by the ''backbone'' molecular weight of the homopolymer linear and branched chains. 38,39 Extensive sets of model materials were prepared to examine the effect of the breadth of the molecular-weight-distribution on the ability to detect low levels of LCB in polyethylene materials.…”

Section: Introductionmentioning

confidence: 99%

“…38,39 Extensive sets of model materials were prepared to examine the effect of the breadth of the molecular-weight-distribution on the ability to detect low levels of LCB in polyethylene materials. 37,40 All materials are based on innovative metallocene catalysts, 2,3,41,42 which are known for their ability to produce polyethylene chains with well-defined structures and reduced polydispersities. Such materials, of course, were not available for many of the studies previously discussed in the literature.…”

Section: Introductionmentioning

confidence: 99%

Detection of low levels of long‐chain branching in polydisperse polyethylene materials

Karjala

Sammler

Mangnus

et al. 2010

J of Applied Polymer Sci

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ABSTRACT:Creep experiments have been applied to probe the zero-shear viscosity, g 0 , of polyethylene chains directly and precisely in a constant-stress rheometer at 190 C. Such experiments, when combined with precise measurements of the weight-average molecular weight, M w , calibrated relative to linear chains of high-density polyethylene, are shown to provide a very sensitive approach to detect low levels (0.005 branches per 1000 carbons) of long-chain branching (LCB). This detection limit is shown to be insensitive to whether the molecular weight distribution (MWD) breadth, M w /M n , rises from about two to ten.

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Detection of Low Levels of Long-Chain Branching in Polyolefins

Cited by 7 publications

References 0 publications

Influence of polypropylene topological structure evolution during melt branching reactive processing on its melt performances

Influence of polypropylene topological structure evolution during melt branching reactive processing on its melt performances

Methods of long chain branching detection in PE by triple‐detector gel permeation chromatography

Detection of low levels of long‐chain branching in polydisperse polyethylene materials

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