A light‐scattering study of low pressure polyethylene fractions

Tung, L. H.

doi:10.1002/pol.1959.1203613023

Cited by 63 publications

(7 citation statements)

References 12 publications

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“…A less complicated and widely used indirect method is the measurement of the limiting viscosity number (L VN) known also as the intrinsic viscosity [1]]. This yields a viscosity average molecular weight, which is usually close in value to the weight average molecular weight.…”

Section: Introductionmentioning

confidence: 99%

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The Mark–Houwink–Sakurada Equation for the Viscosity of Linear Polyethylene

Wagner¹

1985

Journal of Physical and Chemical Reference Data

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In this review, the parameters K and a found in the literature for the Mark-Houwink-Sakurada equation relating viscosity to molecular weight have been critically evaluated. for linear polyethylene, and values have been recommended for six commonly used sol-· vents. These are decalin, 1,2,4-tricholorobenzene, l-chloronaphthalene, tetralin, o-dichlorobenzene, and p-xylene. In addition, the literature values of K for several different theta solvents are presented.

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Section: Introductionmentioning

confidence: 99%

“…The molecular weight range of the fractions is only from 20 000 to 188 000. Their values for the Mark-Houwink constants result in the equation[1]] =50.6X 10-3 MO. 7 mLlg at 138°e.…”

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confidence: 99%

The Mark–Houwink–Sakurada Equation for the Viscosity of Linear Polyethylene

Wagner¹

1985

Journal of Physical and Chemical Reference Data

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“…In principle, lowpressure processes (chromium-based and Ziegler-Natta type catalysts, developed in the 1950s and 1970s, respectively) yield linear species. However, the possible existence of LCB in high molecular weight fractions of this type of polymer was first suspected by Tung [60]. Many investigators found evidence of LCB in supposedly linear HDPEs [61][62][63].…”

Section: Conventional Polymersmentioning

confidence: 99%

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

et al. 2002

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Abstract:The aim of this review is to provide evidence that rheological testing is a potent tool for characterising polymers in the melt. An effort has been made in order to gather results in conventional and model polyolefins, and correlating them with phenomena occurring at the molecular level. We have focused our interest on long chain branching (LCB). In the case of materials containing long side-chain branches, strong effects on viscosity, elastic character and activation energy of flow are general features. Literature results mostly indicate that the effect of polydispersity on these parameters could be very similar to that expected due to the presence of LCB -notwithstanding that the effects of LCB seem to be stronger than those due to polydispersity for a given molecular weight. Different relaxation processes appear as a consequence of the presence of LCB: slower terminal relaxation behaviour than of linear counterparts, and faster additional branch relaxation at higher frequencies, clearly distinguishable from polydispersity effects. To measure the amount of LCB from limited viscoelastic data and molecular properties seems to be a suitable instrument to explain the rheological features of the different polymers, but it fails when the results are compared with measured values of LCB density in model polymers. The actual framework leads us to say that the number of branches is less important than the topology itself. Therefore, the position and architecture of the branches along the polymer main chain are the main factors that control the rheology of the material.

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“…In a comparison with the extraction of polystyrene on a column of uniform temperature it was shown that the sample was redistributed and the resolution somewhat improved with the thermal gradient.% On the other hand, there are reports where the fractionation is no better or even worse with a thermal gradient. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In part, these comparisons reflect the unexpected resolution that can be achieved by direct extraction but they also suggest that a proper balance of conditions may be needed to gain an advantage using the thermal gradient. On the basis of a simple analysis Hulme8s has concluded that a steep thermal gradient would accumulate polymer in the cooler zones and thereby offset the advantage gained by refractionation.…”

Section: Precipitation Chromatographymentioning

confidence: 99%

Review of solution methods and certain other methods of polymer fractionation

Schneider

1965

J. polym. sci., C Polym. symp.

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Discrimination in terms of solubility differences forms the basis of the most widely applicable methods of polymer fractional ion. These include fractional precipitation and extraction on a batch scale; the rapid column methods, namely, the elution method and precipitation chromatography; and turbidimetric titration, which is strictly an analytical procedure. The principles of solution fractionation are reviewed as applied to batch fractionation and to the column methods, and certain essential differences are pointed out between these two approaches. The importance of proper solvent selection in the several methods is considered, and examples are presented of fractionation on the basis of chemical and structural differences as well as in terms of molecular weight. A brief summary is also presented on the present status of certain other methods, including thermal diffusion, none refining, and adsorption chromatography, which utilize different physical principles as the basis of separation.

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A light‐scattering study of low pressure polyethylene fractions

Cited by 63 publications

References 12 publications

The Mark–Houwink–Sakurada Equation for the Viscosity of Linear Polyethylene

The Mark–Houwink–Sakurada Equation for the Viscosity of Linear Polyethylene

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

Review of solution methods and certain other methods of polymer fractionation

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