The flow behavior of molten polyethylene resins has been studied with rotationa14J3 and parallel plate viscometers6 and piston-or gas-driven capillary rheometers. 1,2,9v12,19r21122 Results obtained from different types of instruments are often in Three commercial resins were studied, two of low disagreement. During these measurements, the density and one of high density. Their characterissame resin sample is subjected to long heating times viscosities were measured as a function of shear and temperature.
Articles you may be interested inThe effect of an axial electric field on the stability of a rotating dielectric cylindrical liquid bridge When a portion of a liquid dielectric was sUbjected to an electric dc field of hi~h intensity, the level r?se locally. The maximum rise attained by different liquids above the liquid level outside the field mcreased with their dielectric constant and polarizability. , The following observations indicate that electrostriction rather than e:ectr~pho~e~ls was the cause of t~e observed rise in liquid level. (a) Molten polymers, which have such high VISco~ltles that ~Iec~ro~horettc motion of ions or charged particles is virtually suppressed, rose to the same helght~ as flUid hqUids. (b) Neither inverting the direction of the field nor (c) adding 0.05% finely disper~ed alummum.or ~,15% ultramarine powder to molten polyethylene affected the rise in the dc fie~d q~alitatt.vely or quantttattvely, Repulsion occurred in very high fields, producing a slight depreSSIOn In the hqUid level.
The melt extrusion of a commercial polypropylene resin was studied with a screw extruder and a series of capillary dies of length:radius ratios varying from 0 to 65. Three temperatures and the range of shear rates encountered in industrial processing were covered. The temperature dependence of the apparent melt viscosity of polypropylene was intermediate between linear and branched polyethylene. Extrapolated zero shear activation energy for viscous flow was 9 ± 1 Kcal/mole. Shear dependence of the apparent viscosity of polypropylene melt was greater than for branched polyethylene in turn, greater for linear.
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