Volume 29, Issue 1, February 1985
Index of content:
Measurement of Fast Transient and Steady‐State Responses of Viscoelastic Fluids with a Sliding Cylinder Rheometer Executing Coaxial Displacements29(1985); http://dx.doi.org/10.1122/1.549783View Description Hide Description
A sliding cylinder rheometer (SCR) has been constructed for use with an existing materials test system (MTS) for the measurement of fast transient and steady‐state responses of viscoelastic fluids in simple shear. This MTS‐SCR combination capitalizes on the versatility and capability of the MTS programmable drive system, while the design of the SCR ensures the ideal simple shearing configuration. Experience with this new system indicates that SCR is not only less expensive to construct but also easier to use than the parallel‐plate rheometer (PPR). Instrumental compliance, material inertia, and mechanical lag in both the input and output components of the system are minimal. Reproducible shear stress data on a polyisobutylene‐in‐decalin solution have been obtained for various complicated flow programs.
29(1985); http://dx.doi.org/10.1122/1.549784View Description Hide Description
A parallel‐disk viscometer capable of measuring the viscosity rise isothermally for fast polymerizing systems has been designed and characterized. Criteria for isothermal operation are given. The viscometer has been specifically designed for polyurethane chemical systems used in reactioninjection molding (RIM) and is adaptable enough to be coupled directly to various commercial RIM machines. Some minor modifications may be needed for other reactive systems. The viscometer in its present design is not highly precise, but is rugged and inexpensive.
29(1985); http://dx.doi.org/10.1122/1.549785View Description Hide Description
The flow of a creeping polar fluid between two eccentric rotating cylinders is analyzed. A perturbation series is applied to solve the system of partial differential equations. The dependence of the velocity components and the spin on the coupling number N and the length ratio L is discussed.
29(1985); http://dx.doi.org/10.1122/1.549786View Description Hide Description
The article presents a method for modeling the response of a class of thermorheologically complex viscoelastic materials. For the type of materials considered, all temperature effects can be correlated through horizontal and vertical shift factors. In addition, the proper evaluation of transient temperature response requires the vertical shift to be represented as a product of two temperature‐dependent functions. It is shown that, in order to obtain complete information, it is necessary to conduct sharp temperature‐drop tests in addition to isothermal creep and recovery experiments. The method and its use are demonstrated for the specific case of Hercules 3502 epoxy resin.
29(1985); http://dx.doi.org/10.1122/1.549811View Description Hide Description
The flow behavior of aqueous and organic polymer solutions in laminar flow was studied experimentally in small‐diameter tubes. The tube diameters ranged from 0.0190 to 0.1097 cm and the (length/diameter) ratios were 20–2700. The experimental flow rates were abnormally higher than the predictions based on viscometric cone‐and‐plate data. This abnormal flow enhancement is termed here apparent slip and it was quantified by an effective slip velocity. The effective slip velocity was found to increase with the wall shear stress. The contribution of slip, however, to the total flow rate for a given tube diameter decreased with increasing wall stress due to shear thinning. Additionally, for a given wall stress, the contribution of slip increased with decreasing tube diameter. Qualitatively, the apparent slip phenomenon is expected to occur for the flow of elastic high‐molecular‐weight, nondilute polymer solutions in inhomogeneous stress fields.
29(1985); http://dx.doi.org/10.1122/1.549838View Description Hide Description