Fractionation of polyethylene

Abstract

The relatively rapid Desreux technique for polymer fractionation has been modified and applied to both linear and highly branched polyethylenes. The polymer is precipitated from p‐xylene solution onto a sand column by cooling from 127° to room temperature. After removal of solvent, the column temperature is again raised to 127° and fractions are eluted, using p‐xylene‐ethylene glycol monoethyl ether mixtures of increasing solvent power. Approximately 15 fractions are obtained and polymer recovery is essentially quantitative. The reproducibility of the integral distribution curves is within ±2% for a cumulative weight‐% of 85 or higher. In certain cases difficulty has been encountered in resolving the less soluble portion of the sample. The selective nature of the system is indicated by the fact that the reduced specific viscosities of the highest and lowest molecular weight fractions are generally in the ratio of 50 or higher.

Molecular Weight Dependence on the Morphological Properties of Polyethylene Gels

“…The specific viscosity IJsp is defined by IJsp=IJ/'lo-1, in which 11 and 'lo are the viscosities of solution and solvent, respectively. The viscosity-average molecular weight Mv in Table I 6.77x 10-4 and a=0.67, 21 in which [17] is defined by lim'1sp/c (c, concentration). In the concentration range below 10 gjlOOml, '1sp/c of the specimen G201 shows a gradual linear increase while these of other specimens 6009, 4551 H, and 5551 H show a remarkably increasing curve and the degree of the increase becomes considerable with increase in molecular weight of the specimens.…”

High efficiency synthesis of isotactic polypropylene and linear polyethylene using a new C2-symmetric carbon-bridged zirconocene catalyst

“…The precipitated polymer was collected by filtration and washed with ethanol for several times and then dried in vacuum at 60 °C to a constant weight. [4] and that of PE according to the equation [5] [η] = 6.67× 10 -4 M v 0.67 , respectively. The weight-average molecular weight (M w 's) and the molecular weight distribution of some polymers were determined by the gel-permeation chromatography method on a Waters 150ALC/GPC system in a 1,2,4-trichlorobenzene solution at 135 ℃, using polystyrene columns as a standard.…”

Zirconium complexes with versatile β-diketiminate ligands: Synthesis, structure, and ethylene polymerization

“…The intrinsic viscosities of polyethylenes (PE) were measured with an Ubbelohde viscometer in decahydronaphthalene at 135°C. The viscosity average molecular weights of PEs were calculated according to the equation: [g] (dL/g) = 6.77 Â 10 À4 M g 0.67 [57]. The gel permeation chromatography (GPC) performed on a Waters 150 ALC/GPC system in a 1,2-dichlorobenzene solution at 135°C was used to determine the weight-average molecular weights (M w ) and the molecular weight distributions (M w /M n ) of the polymers.…”