Viscosity temperature-dependent

A kinetic study for the polymerization of styrene, initiated with n BuLi, was designed to explore the Trommsdorff effect on rate constants of initiation and propagation and polystyryl anion association. Initiator association, initiation rate and propagation rates are essentially independent of solution viscosity, Polystyryl anion association is dependent on media viscosity. Temperature dependency correlates as an Arrhenius relationship. Observations were restricted to viscosities less than 200 centipoise. Population density distribution analysis indicates that rate constants are also independent of degree of polymerization, which is consistent with Flory s principle of equal reactivity. 

When bounding walls exist, the particles confined within them not only collide with each other, but also collide with the walls. With the decrease of wall spacing, the frequency of particle-particle collisions will decrease, while the particle-wall collision frequency will increase. This can be demonstrated by calculation of collisions of particles in two parallel plates with the DSMC method. In Fig. 5 the result of such a simulation is shown. In the simulation [18], 2,000 representative nitrogen gas molecules with 50 cells were employed. Other parameters used here were viscosity /r= 1.656 X 10 Pa-s, molecular mass m =4.65 X 10 kg, and the ambient temperature 7 ref=273 K. Instead of the hard-sphere (HS) model, the variable hard-sphere (VHS) model was adopted in the simulation, which gives a better prediction of the viscosity-temperature dependence than the HS model. For the VHS model, the mean free path becomes ... 

Viscosity temperature dependence in ILs is more complicated than in most molecular solvents, because most of them do not follow the typical Arrhenius behavior. Most temperature studies fit the viscosity values into the Vogel-Tammarm-Fulcher (VTF) equation, which adds an additional adjustable parameter (glass transition temperature) to the exponential term. 

Nahme-Griffith Na aATBr a Viscosity temperature dependence... 

Physical or material quantities thermal conductivity k, density p, specific heat Cp, viscosity vo = v To), and viscosity temperature dependence a, from p =... 

The practical advantage of these relations is that, in MD simulations, single molecule properties like the self-diffusion coefficient and rotational relaxation times converge much faster than system properties due to additional averaging over the number of molecules in the ensemble. We applied eqs. 10 and 11 to our MD results using data at 800 K as a reference point in order to predict the viscosity over the entire temperature interval. In Fig. 7 we compare the predicted values with those obtained from simulation. It appears that in the temperature interval 600 K to 800 K predictions of Eq. (10) are more consistent with MD results than are the predictions of Eq. (11). This leads us to conclude that the viscosity temperature dependence in liquid HMX is more correlated... 

It is possible, however, to correct isothermal data to constant friction factor if the viscosity-temperature dependence is known at each ( )- Thus, Fig. 20b shows calculated from tjr according to Eq. (2.30) using the empirical dependence of and on (here Z is constant and 0.1 q) 1.0). Two regions can be clrarly discerned, one with slope 3.4, the other with slope 1.0. Moreover, the solid curve represents the empirical relation found for pure polymer as a function of X. Thus, the observation that the effect of diluent can be accounted for by the inclusion of q> in the definition for X given in Eq. (2.6) is verified. 

Silicate melts suitable for fiber production have to fulfill many requirements first a sufficient fiber drawing potential, which is dependent upon the ratio of surface tension to viscosity. Fixing of the molten filament in the form of a fiber is a consequence of the increase in vi.scosity with decreasing temperature. Got)d fiber formation requires a viscosity-temperature dependence which is relatively flat. The glass must also not exhibit a tendency to crystallization. 

Figure 3.15 Test of the mode coupling theory power law predictions for viscosity temperature dependence for a variety of molecular and ionic liquids. Tg is the glass transition temperature determined by thermal analysis at 10 K/min scanning (After Angell, 1998).

DEVELOPMENT OF A NOVEL METHOD FOR EVALUATION OF THE VISCOSITY-TEMPERATURE DEPENDENCY OF LIQUIDS USING THE UMSTAETTER EQUATION. 

LC Material Binary Mixture of N +Np, Selection of Nn Optical and DielectricaL Properties of LC Optical Properties of LC Viscosity Temperature Dependence of Vth... 

McCabe, C., Cummings, P. T., and Cui, S. T. 2001. Characterizing the viscosity-temperature dependence of lubricants by molecular simulation. Fluid Phase Equilibr. 183-184 363. 

The purpose of this peper Is to present a new method for incorporating thermal affects into the calculated performance of laminar lubricating films. There is enormous interest in the inclusion of such effects, as the recent reviews of Xhonsari (1,2) attest. The reason for this interest is well founded, since the viscosity-temperature dependence of typical lubricants is such that the viscosity can vary many fold across and along a bearing film, with attendant effects on load capacity. 

Long chain branching (LCB) has several benefits relating to the polymer processability because it affects melt viscosity, temperature dependence of viscosity, melt elasticity, shear thinning, and extension thickening. The effect of LCB on the melt-state properties of polyethylene depends on the number, length, and distribution of the branches, on molecular weight, and on MWD. 

Viscosity-temperature dependence of a typical soda-lime-silicate glass is shown in Fig. 5.21. Glass is melted at around 1450°C, delivered to a forming machine around 1000°C, placed on a conveyor belt as a formed product at temperatures lower than about 700°C, and annealed between 530°C and 480°C. 

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