No abstract

No abstract

The flow curves for two samples of molten polyethylene and one of plasticized polyvinylbutyral were measured in a large range of rates of shear and shearing stresses. Two conicylindrical viscometers of greatly different dimensions were used to obtain the wide ranges; the data from these viscometers coincided in the region of overlapping. The behavior of the molten plastics is essentially parallel to the one for solutions of high polymers. Absolute values of the initial viscosity of these polyethylenes at different temperatures were close to those obtained by Dexter on other polyethylenes. The apparent activation energy for viscous flow calculated from these experiments was very similar to the ones reported in the literature.

A kinetic theory for polymer melts. V. Experimental comparisons for shearflow rheological properties rather than n itself for Jarge n. This is because the energy required to vaporize a large molecule can be thought of as a surface energy.28,29 The heats of vapori~ zation reported by Mazee lo tend to support this view since they are approximately proportional to n l over the range C21-C43• They are, however, inconsistent with 28 The correlation of normal stress with the shear stress and flow birefringence of flowing solutions has been extended to include the recoverable shear strain s which can be measured directly by a rotational viscometer in "recoil." This has been shown experimentally with solutions of a high-viscosity nitro-cellulose in n-butyl acetate and a viscous polyisobutylene. These results show that the principal axes of the tensors of stress, strain, and optical anistropy coincide, even when no constant shear modulus (shear compliance) exists.

No abstract