Viscosity, as a function of temperature

Melt Viscosity. The study of the viscosity of polymer melts (43—55) is important for the manufacturer who must supply suitable materials and for the fabrication engineer who must select polymers and fabrication methods. Thus melt viscosity as a function of temperature, pressure, rate of flow, and polymer molecular weight and stmcture is of considerable practical importance. Polymer melts exhibit elastic as well as viscous properties. This is evident in the swell of the polymer melt upon emergence from an extmsion die, a behavior that results from the recovery of stored elastic energy plus normal stress effects. 

Correlation Methods This section briefly discusses methods for correlating viscosities as a function of temperature and presents the most common accurate methods for prediction of vapor and hqiiid viscosity. 

Viscosities of the siloxanes were predicted over a temperature range of 298-348 K. The semi-log plot of viscosity as a function of temperature was linear for the ring compounds. However, for the chain compounds, the viscosity increased rapidly with an increase in the chain length of the molecule. A simple 2-4-1 neural network architecture was used for the viscosity predictions. The molecular configuration was not considered here because of the direct positive effect of addition of both M and D groups on viscosity. The two input variables, therefore, were the siloxane type and the temperature level. Only one hidden layer with four nodes was used. The predicted variable was the viscosity of the siloxane. 

Figure 8 CTPB viscosity as a function of temperature and plasticizer content.

FIGURE 7.7 Plots of viscosity as a function of temperature from left to right, (a) General plot showing the desired temperature range where viscosity is approximately constant as temperature is varied, (b) plot for a high T material, and (c) plot for a low T material where RT = room temperature. 

Models of the intimate contact process that have appeared in the literature are commonly composed of three parts or submodels. The first submodel is used to describe the variation in the tow heights (surface waviness or roughness) across the width of the prepreg or towpreg. The second submodel, which is used to predict the elimination of spatial gaps and the establishment of intimate contact at the ply interfaces, relates the consolidation pressure to the rate of deformation of the resin impregnated fiber tow and resin flow at ply surface. Finally, the third submodel is the constitutive relationship for the resin or resin-saturated tow, which gives the shear viscosity as a function of temperature and shear rate. 

Rule 1. Fit experimentally measured viscosities as a function of temperature for the pure species to Eq. 12.100 (presented later), using e and a as the adjustable parameters. Measured viscosities are generally more reliable than thermal conductivities for extracting these parameters. 

Attempts to give a quantitative analysis of plastisol extrusion were undertaken only in a few published papers. They were based on the analysis of plastisol viscosity as a function of temperature and time. If in the processing of thermosetting plastics their viscosity is assumed as practically independent of time (except of materials sensitive to structural and chemical transformation in temperature and stress fields which are accompanied by thermo-mechanical decomposition and cross-linking of macromolecular chains, the extent of the larter being influenced by the time of exposure to thermal and mechanical loads 18-21)), then at extrusion of plastisols, in view of their gelatination, the additional condition should be satisfield ... 

It was just stated that the viscosity of liquids and dispersions usually decreases as temperature increases. An exception is the case of gases whose viscosities usually increase slightly with temperature, with a temperature coefficient of about 0.3% per degree Kelvin [383]. The viscosities of liquids usually decrease with increasing temperature, and more strongly. A number of equations, of varying degrees of complexity, have been formulated to enable one to empirically predict liquid viscosities as a function of temperature [384—386]. A simple, often used, relation is the Andrade equation,... 

Figure 11. Dynamic shear viscosity as a function of temperature for poly-(styrene-b-butadiene-b-styrene) at various angular frequencies (77)...

Fig. 3.2. Molten sulfur viscosity as a function of temperature (Tuller, 1954). The viscosity minimum at 430 K and the enormous viscosity increase just above 430 K are notable.

Figure 3.49 Viscosity as a function of temperature for IM, 3M and SM aqueous di-methylsulfoxide (DMSO) solutions. Solid curves are curve fits to the data ba on the exponential expression tj = tj, exp [ACocf (IVT - INT )], where T is absolute temperature in Kelvin, R is the universal gas content, A o is the activation energy, Tp is the phase change temperature, and r)pi, is the viscosity of the solution at the phase-change temperature. The dashed curve is the exponential curve fit for water, and the dashed circles indicate the region of temperature where phase change occurred. (Reprinted with pennis-sion. See Ref. [72aJ. 1993 ASME International.)...

Figure 4. Reduced viscosity as a function of temperature for several values of the reduced pressure. (Reprinted mth permission from Ref. 12, Fig. 1.3-1, 1960, John Wiley and Sons.)...

Figure 11.5 Complex dynamic viscosity as a function of temperature for a main-chain polyether consisting of a methyl stilbene mesogen and a mixture of seven-and nine-carbon aliphatic spacers. The polymer has a molecular weight of 36,000. The diamonds and squares are for temperature ramp rates of 0.1 °C and 2.0°C/min, respectively the open and closed symbols are for heating and cooling, respectively. The dashed line marks the isotropic-nematic transition. (From Gillmor et al. 1994, with permission from the Journal of Rheology.)...

There is one other method of determining the activation energy for the second process. From the compliance curves due to the second meclmnism, one can calculate the viscosity as a function of temperature. A plot of the viso)sily as a function of temperature logj vs. 1/T) (not shown) yields a much higher activation energy than 50 Kcal. This is not surprising, however, because for a relaxation mechanism of the type encountered here,... 

A regression fit to the bulk viscosity as a function of temperature, provided AE = 34.7kJ/mol) and A5 , = 9.87J/mol-K. The flow-activation energy is close to that reported for bulk Zdol with a molecular weight of 3100 in Refs. . A positive value for the flow activation entropy of bulk Zdol means that the entropy of the flow unit increases on going into the flow-activated state. 

Formulas and Data Sheets, issued yearly, containing all newly established fundamental equations and numerical data on basic properties of polymers. These would include new equations to express viscosity as a function of temperature, concentration, or shear rate new relations between intrinsic viscosity and molecular weight new formulas on the kinetics of polymerization and copolymerization data on second-order transition points of new polymers or copolymers heat and entropy of solution, dilution, melting, and swelling of macromolecules and similar fundamental data as they are contained in the articles appearing during the reference year. They would be similar in purpose to the Technical Data Sheets and complement them in regard to fundamental information. 

Activation energy for self-diffusion in viscous flow may be calculated from Eq. (47) by measuring the kinematic viscosity as a function of temperature. The activation energy for the self-diffusion through NPOE membrane was 24 kj/mol [42]. 

Vmhi - the minimum viscosity (as a function of temperature) for injection or transfer moulding, and... 

Compared with the mineral-based fluids, these fluids exhibit reduced variation in viscosity as a function of temperature, which removes the requirement for a VI improver to be added. PAO-based hydraulic fluids also demonstrate outstanding reliability under mechanical stress and excellent chemical and thermal stability. The fluid developed was given the NATO designation H-537 and is controlled by the US military specification MIL-PRF-83282. In contrast to the mineral-based H-515 this fluid has a PMC flash point in the region of 215°C which is a considerable increase. 

The DIPPR project (5) was selected for viscosity of gas. Data for gas viscosity as a function of temperature were correlated using Equation (1-7). Results are in favorable agreement with data. Errors are about 1-10% or less in most cases. 

Results from the DIPPR project (5) were selected for viscosity of gas. Since the chemical structure of vinylidene chloride is between that of vinyl chloride and trichloroethylene, the values for vinylidene chloride were estimated from values for vinyl chloride and trichloroethylene. In the absence of data, this estimate should be considered a rough approximation. Data for gas viscosity as a function of temperature were correlated using Equation (1-7). Results are in favorable agreement with data. Errors are about 10% or less in most cases. 

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