Recoverable Creep Compliance Research Articles

Rheological properties of rodlike polymers in solution. IV. Rheology of blends of nylon and a rodlike chain

Rheological and rheo‐optical properties are studied for homogeneous blends of the rodlike poly(1,4‐phenylene‐2,6‐benzobisthiazole), PBT, and poly(hexamethylene adipamide), nylon‐66. The linear recoverable creep compliance shows that the distribution of retardation times is similar for all the blends studied, though shifted on the time scale by large variation in the viscosity among the blends. A single‐integral (BKZ‐type) constitutive equation is found adequate to represent the dependence on shear rate of the nonlinear steady‐state viscosity, the recoverable compliance, and the flow birefringence (save for certain anomalous behavior at low shear rate in the latter case). Effects on the viscosity are discussed in terms of a simplified model for behavior when a characteristic rheological time constant is longer for the rodlike (PBT) than for the flexible chain (nylon‐66) component.

Viscoelastic behavior of polystyrene‐tricresyl phosphate solutions

AbstractThe viscoelastic behavior of solutions of a narrow molecular weight distribution polystyrene in tri‐m‐toly 1 phosphate has been determined from the glassy to the terminal zones of response. The polymer concentration was varied from one to 100% thereby providing for the first time a complete picture of the influence of a solvent on the time‐dependent response of a polymer.A computer analysis, governed by human judgment, has been used to extract retardation spectra which can be used to regenerate the reduced recoverable creep compliance curves within the scatter bands of the data. With the resulting retardation spectra, dynamic compliance and moduli curves have been calculated.

Magnetic bearing torsional creep apparatus

AbstractA torsional creep and recovery apparatus has been designed and constructed to measure extremely wide ranges of recoverable creep compliance (10−10 to 10−2 cm.2/dyne) and viscosity (10−1 to 1016 poises) within the temperature range −60 to 220°C. Friction is avoided by supporting the moving element, the rotor, in a magnetic field, inducing the required torque with a drag cup motor, and monitoring the angular displacement with a light lever and a light following recorder. Measurements of recoverable compliance can be made further into the region of time scale which is dominated by viscous deformation than has been heretofore possible. In situ sample manipulation of viscoelastic liquids is utilized. Measurement is made on liquid cylinders between circular stainless steel platens. Results which have been obtained on a 1.22 × 105 molecular weight polystyrene are presented to illustrate the range of possible measurements and to indicate the value of such results covering up to six logarithmic decades of time scale.