Analysis of Chain Branch of Polyolefins by a New Proton NMR Approach

Jung, Min-Hwan; Lee, Yura; Kwak, Sooyoung; Park, Heeyong; Kim, Byoungsoo; Kim, Sulhee; Lee, Kwang Hwan; Cho, Hye Sung; Hwang, Kwang Yeon

doi:10.1021/acs.analchem.5b04357

Cited by 21 publications

(23 citation statements)

References 38 publications

(60 reference statements)

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“…The polymer chain mobility increases with increasing free volume . LDPE contains both LCBs (at least 1–2 per 1000 carbons) and SCBs (10–50 per 1000 carbons) . This level of branching in LDPE leads to remarkably strong shear thinning and a low melt viscosity during extrusion, which results in good processability, e.g., in the case of extruded HVDC‐cable insulation materials.…”

Section: Polyethylene Nanocomposites For High Voltage Insulationmentioning

confidence: 99%

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

2017

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Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite.

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Section: Polyethylene Nanocomposites For High Voltage Insulationmentioning

confidence: 99%

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

2017

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“…Melting point and crystallinity values obtained from second heating of DSC thermograms are listed in Tables and . The crystallinity of polyethylene, which significantly affects the properties of the polymer, is quite sensitive to the concentration of its branches . The polymers produced using the nickel‐based catalyst have low melting point due to much more branches and weaker intermolecular forces that was confirmed using NMR spectroscopy.…”

Section: Resultsmentioning

confidence: 78%

Single and binary catalyst systems based on nickel and palladium in polymerization of ethylene

Kimiaghalam

Nasr‐Isfahani

Zohuri

et al. 2017

Applied Organom Chemis

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The catalyst (N,N‐bis(2,6‐dibenzhydryl‐4‐ethoxyphenyl)butane‐2,3‐diimine)nickel dibromide, a late transition metal catalyst, was prepared and used in ethylene polymerization. The effects of reaction parameters such as polymerization temperature, co‐catalyst to catalyst molar ratio and monomer pressure on the polymerization were investigated. The α‐diimine nickel‐based catalyst was demonstrated to be thermally robust at a temperature as high as 90 °C. The highest activity of the catalyst (494 kg polyethylene (mol cat)−1 h−1) was obtained at [Al]/[Ni] = 600:1, temperature of 90 °C and pressure of 5 bar. In addition, the performance of a binary catalyst using nickel‐ and palladium‐based complexes was compared with that of the corresponding individual catalytic systems in ethylene polymerization. In a study of the catalyst systems, the average molecular weight and molecular weight distribution for the binary polymerization were between those for the individual catalytic polymerizations; however, the binary catalyst activity was lower than that of the two individual ones. The obtained polyethylenes had high molecular weights in the region of 105 g mol−1. Gel permeation chromatography analysis showed a narrow molecular weight distribution of 1.44 for the nickel‐based catalyst and 1.61 for the binary catalyst system. The branching density of the polyethylenes generated using the binary catalytic system (30 branches/1000 C) was lower than that generated using the nickel‐based catalyst (51/1000 C). X‐ray diffraction study of the polymer chains showed higher crystallinity with lower branching of the polymer obtained. Also Fourier transform infrared spectra confirmed that all obtained polymers were low‐density polyethylene.

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“…We then turned to a pulse sequence which decouples a single frequency (Bruker zghd.2). 20 Finding the optimal decoupling frequency for M protons with Jung's approach 20 can be time-consuming, as the frequency may depend on several factors, such as solvent and temperature. Our approach is to start by surveying homonuclear couplings with a few minutes of a short COSY experiment, resulting in an easier and reliable way to find the correct decoupling frequency for M protons.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…20 1 H NMR approach can be very effective for NMR analyses when only a limited amount of sample material is available, such as when analyzing polyolefin film layer compositions or fractions of an analytical chromatographic separation. In this paper, we describe an improved 1 H NMR approach which was originally proposed by Jung et al 20 An improved technique for finding optimal decoupling frequency is discussed and a new 1 H NMR pulse sequence with homodecoupling is proposed. We offer suggestions regarding simple method to calculate SCB/1000C (and potentially SCBD) along with the proper use of heteronuclear single quantum coherence (HSQC) for SCB analyses.…”

mentioning

confidence: 99%

Analyses of Short Chain Branches in Polyolefins with Improved ¹H NMR Spectroscopy

Zhou¹,

Paradkar²,

Cong³

et al. 2020

Anal. Chem.

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Polyolefin microstructures, for example, short chain branching (SCB) and short chain branch distribution (SCBD), have a direct impact on properties and thus ultimately influence end-use applications. The 1 H NMR approach to analyze SCB and SCBD is particularly useful when only a limited amount of sample is available, for example, polyolefin film layers or the fractions from polyolefin separation techniques, such as gel permeation chromatography (GPC), crystallization elution fractionation (CEF), high temperature liquid chromatography (HTLC), and thermal gradient interaction chromatography (TGIC). In this paper, we discuss the best approach to find a good decoupling frequency and propose an improved 1 H pulse sequence with homonuclear decoupling for better measuring SCB. With this new pulse it is possible to reach a S/N of 10 (level of quantification) for the methyl signal from SCB in an ethylene−hexene copolymer (EH, 3.6 mol % H) in 3.5 min with 0.5 μg of sample. We also show an easy method to calculate SCB/1000C and demonstrate the proper use of heteronuclear single quantum coherence (HSQC) to measure SCB in a complicated system. A very quick approach to examine the presence of a small amount of LDPE in a polyolefin sample is also suggested, which can reduce NMR acquisition time from a couple of days to a few minutes.

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Analysis of Chain Branch of Polyolefins by a New Proton NMR Approach

Cited by 21 publications

References 38 publications

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

Single and binary catalyst systems based on nickel and palladium in polymerization of ethylene

Analyses of Short Chain Branches in Polyolefins with Improved ¹H NMR Spectroscopy

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Analysis of Chain Branch of Polyolefins by a New Proton NMR Approach

Cited by 21 publications

References 38 publications

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

The Role of Interfaces in Polyethylene/Metal‐Oxide Nanocomposites for Ultrahigh‐Voltage Insulating Materials

Single and binary catalyst systems based on nickel and palladium in polymerization of ethylene

Analyses of Short Chain Branches in Polyolefins with Improved 1H NMR Spectroscopy

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Analyses of Short Chain Branches in Polyolefins with Improved ¹H NMR Spectroscopy