Showing papers by "Guy C. Berry published in 1989"
TL;DR: In this paper, an eddy-current torque transducer and an air-bearing suspension are coupled with a computer-based data acquisition system and permits studies of shear deformation for several strain or stress histories.
Abstract: A rheometer utilizing an eddy-current torque transducer and an air-bearing suspension is described. The rheometer is coupled with a computer-based data acquisition system and permits studies of shear deformation for several strain or stress histories. A sinusoidal stress history is used to determine the shear storage and loss compliances J′(ω) and J″(ω), respectively. Step stress histories are used to determine the shear creep compliance J(t) and the recoverable complaince R(t) or more complicated linear and nonlinear rheological responses related to these. Deformation at constant strain rate is used to determine the stress growth function or the steady-state viscosity. The rheometer may be used over the temperature range – 10–180°C, with torque from 1 to 106 dyn cm, and is adaptabel to use with a variety of sample geometrical shapes (e.g., cone and plate, parallel plate, etc.). Examples of measurements on on viscoelastic fluids and on gels below their yield strain are given.
7 citations
TL;DR: In this paper, the tensile creep and recovery behavior of the rod-like poly(1,4-phenylene-2,6-benzobisthiazole), PBT, in polyphosphoric acid, PPA, have been studied to reveal a solid-like behavior with a substantial Young's modulus.
3 citations
3 citations
TL;DR: In this article, isotropic solutions of rod-like poly(p-phenylene benzbisoxazoles), PBO, flexible chain poly(2,5-benzoxazole), ABPBO, and their miscible blends in solution are described.
Abstract: Rheological properties of isotropic solutions of rodlike poly(p-phenylene benzbisoxazole), PBO, flexible chain poly(2,5-benzoxazole), ABPBO, and their miscible blends in solution are described. Measurements include steady state properties (the viscosity and recoverable compliance as functions of shear rate), transient properties (the recoverable compliance), and dynamic mechanical properties (the loss and storage compliances as functions of frequency). The relaxation spectrum of the blends is broader than that for the rodlike chain, and tends to occur at longer times, reflecting a viscosity enhancement that occurs with the blends. The measured zero shear viscosities for rod and blend solutions are compared with predictions based on the model of Doi and Edwards.