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

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

doi:10.1002/app.32720

Cited by 11 publications

(4 citation statements)

References 43 publications

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“…Detailed information is listed in Table . The molecular weight measurement was performed according to the ref , . The molecular weight of iPP was reported using a factor of 0.67 to convert polystyrene equivalent molecular weight to propylene equivalent molecular weight M w .…”

Section: Methodsmentioning

confidence: 99%

Fabrication of Graphene-Coated Silica Particles for Polymer Chromatography to Quantify Chemical Composition Distribution of Polyolefin Materials

Cong¹,

Cheatham²,

Hollis³

et al. 2021

Macromolecules

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As the most consumed synthetic polymers globally, polyolefins provide tunable performance at a low production cost. This tunability is achieved by modifying polymer molecular weight or branching characteristics, the latter of which can be quantified by chemical composition distribution (CCD). CCD can be measured using interaction-based techniques relying on graphite-based material as the stationary phase. Interaction-based techniques are classified as solvent gradient or thermal gradient according to the type of gradient that is used to enable the separation of polyolefins. High-temperature thermal gradient interactive chromatography (HT-TGIC) has been the preferred technique as it overcomes the detector shortcomings of solvent gradient interactive chromatography. This work focuses on the HT-TGIC technique and strives to improve the separation resolution by adopting improvements in the stationary-phase packing material. Resolution is greatest with a substrate consisting of nonporous and homogeneous, spherical particles. However, the synthesis of such material with naturally occurring graphite has been a challenge. Here, an innovative yet simple approach to make such particles is described. A core–shell particle with nonporous silica as the core and graphene nanopowder (GNP) as the shell provides this solution. This novel method does not require chemical modification of graphene or silica particles, which has been explored previously as a potential avenue. These core–shell particles were packed into columns and showed an increase in chromatographic performance and separation resolution versus the best HT-TGIC columns currently available.

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Section: Methodsmentioning

confidence: 99%

Fabrication of Graphene-Coated Silica Particles for Polymer Chromatography to Quantify Chemical Composition Distribution of Polyolefin Materials

Cong¹,

Cheatham²,

Hollis³

et al. 2021

Macromolecules

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“…Polyolefin thermoplastic elastomers (TPE-Os) , are high-end polyolefins that can be widely used in automobiles, medical apparatus, photovoltaic cells, etc. Owing to the saturated hydrocarbon composition and unique chain structure, TPE-Os have good corrosion resistance, weatherability, thermostability, and mechanical performance. − Specifically, they are usually copolymers of ethylene/propylene or ethylene/α-olefins consisting of hard and soft chain segments. The former are crystalline polyethylene (PE) or polypropylene (PP) that can form physical cross-linking at room temperature providing rigidity.…”

Section: Introductionmentioning

confidence: 99%

Rheological and Mechanical Study of Comb-Branched Polyolefin Elastomers Containing Macromer Residues

Xiao

Wang

et al. 2023

Macromolecules

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Comb-polyolefin elastomers (CPOEs) with crystalline long-chain branches (LCBes) demonstrate superior mechanical properties and processability. However, fully understanding the effect of LCBes on their material performance remains a huge challenge due to the residue of unreacted polyethylene macromers (PE-Ms). Here, we report a method of blending CPOEs with PE-Ms to study the structure–activity relationship of CPOEs via extrapolation. CPOE samples with different numbers of LCBes (q) between 0.0 and 9.9 and PE-Ms with an M w value similar to the LCBes were prepared and studied. Blending CPOEs with 20–40 wt % of PE-Ms increased the melt fluidity and reduced the zero-shear viscosity (η0) value from 4590 Pa·s to 980 Pa·s without causing phase separation. These CPOEs exhibit dynamic responses with a similar temperature dependence where the time shift factors could be fitted by the same Williams–Landel–Ferry parameters with C1 at 4.88 and C2 at 443 K. For CPOEs with LCBes, as q increased from 1.1 to 9.9, the number of entanglements between the graft points (Z g) decreased from 11.78 to 0.93, and the chain conformation changed from sparse comb (SC) to dense comb (DC), respectively. The maximum η0 value of CPOEs occurs at the turning point of SC and DC, where Zg is equal to the entanglement number of the branched chain −Z bc of 4.72. Our study distinguished the different effects between the grafted and free PE-Ms on the CPOEs, enabling an in-depth understanding of macromolecular engineering in polymer and facilitating the future development of higher-performance CPOEs or other grafted polymers.

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“…On the other hand, long branches (long chain branching, LCB) and branches of various lengths as well as branches on branches are present in high pressure polymerized low density PE (LDPE) and in some LLDPE. A 13 C‐NMR experiment enables the determination of the number of branches longer than a hexyl branch and this value is most often referred to as LCB . LCB is usually present in small concentrations in LLDPEs, and often LCB is very difficult to characterize, but it is known that LCB, even in very small concentration (for example, in the range of 0.01 – 0.1 LCB/1000 carbons), can drastically influence the rheological properties of polymer materials .…”

Section: Introductionmentioning

confidence: 99%

“…A 13 C‐NMR experiment enables the determination of the number of branches longer than a hexyl branch and this value is most often referred to as LCB . LCB is usually present in small concentrations in LLDPEs, and often LCB is very difficult to characterize, but it is known that LCB, even in very small concentration (for example, in the range of 0.01 – 0.1 LCB/1000 carbons), can drastically influence the rheological properties of polymer materials . Identification of LCB in LLDPEs often relies on their rheological behavior, as it compares with linear counterparts.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Solvent Gradient Liquid Chromatography of Model Long Chain Branched Polyethylenes

Macko

Brüll

Santonja-Blasco

et al. 2015

Macromolecular Symposia

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Summary:The high-temperature solvent gradient liquid chromatography system 1-decanol/1,2,4-trichlorobenzene/porous graphite Hypercarb TM has been applied to the separation of well-defined model long chain branched (LCB) polyethylenes with different architectures (star, H-type, super H-type, pompom, comb). The model LCB polyethylenes have been prepared by anionic polymerization of butadiene followed by click chemistry. After hydrogenation of the polybutadienes, the LCB samples contain $ 2 mol % ethyl branches randomly distributed along the backbone and the LCB, as is typical for linear low density polyethylene (LLDPE). The results indicate that the LCB does not influence the chromatographic separation substantially. The adsorption characteristics of the LCB copolymers are dominated by the SCB content. The presence of LCB increases the molar mass of the samples; however, the increase in molar mass from 100 kg/mol to 200 kg/mol does not influence chromatographic separations in the applied system of porous carbon and 1-decanol/ 1,2,4-trichlorobenzene.

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

Cited by 11 publications

References 43 publications

Fabrication of Graphene-Coated Silica Particles for Polymer Chromatography to Quantify Chemical Composition Distribution of Polyolefin Materials

Fabrication of Graphene-Coated Silica Particles for Polymer Chromatography to Quantify Chemical Composition Distribution of Polyolefin Materials

Rheological and Mechanical Study of Comb-Branched Polyolefin Elastomers Containing Macromer Residues

High‐Temperature Solvent Gradient Liquid Chromatography of Model Long Chain Branched Polyethylenes

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