Mixing, distributive

Distributive mixing does not exhibit yield point and involves the use of compatible fluids. It is also called extensive mixing. It relies on the extent of deformation or strain to which the polymer melt elements are exposed. The actual stresses involved in the process of compounding are important with respect to their effect on the materials and/or ingredients (additives) in terms of yield stress (Y). 

Barrel surta Dispersion - not good Dispersion - not good Flight, 3 300 

Another important variable to consider for good distributive mixing is the viscosity of the matrix. Low matrix viscosity is most efficient for distributing a minor component. If the minor component is a fluid, then close matching of the viscosities of the matrix and the minor component is optimal. 

7 = shear strain (product of shear rate and average residence time) 

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Motionless mixers continuously interchange fluid elements between the walls and the center of the conduit, thereby providing enhanced heat transfer and relatively uniform residence times. Distributive mixing is usually excellent however, dispersive mixing may be poor, especially when viscosity ratios are high,... 

Flow regimes, operability Residence time distribution Mixing Transport processes Screening Optimization Validation... 

Figure 7.27. Twisted-blade type of static mixer operating in the laminar flow regime (a) Distributive mixing mechanism showing, in principle, the reduction in striation thickness produced (f>) Radial mixing contribution...

Remill batch and final batch rotors should be designed in order to favor distributive mixing and, hence, optimized cooling effect. 

FIGURE 35.19 High distributive mixing (HDM) rotor design (tangential) of Pomini SpA. 

It appears from formula (6) that the prior-prejudice distribution mix) is a fundamental quantity in the calculation of the MaxEnt distribution of electrons, in that the latter is obtained by modulation of m(x). In all those regions where the modulating factor required to fit the observations is unity, the final picture is therefore always going to coincide with the prior expectation itself. For this reason, it is of the greatest importance that some of the prior information available about the system under study be conveyed into the calculation by means of a sensible choice for the prior-prejudice distribution. 

The phenomenon can be illustrated by considering a model density q(x), from which diffraction data can be computed at arbitrarily high resolution. The (normalised) exponential factor needed to reconstruct q(x) by MaxEnt modulation of a chosen prior-prejudice distribution mix) can be written as... 

Figure 1 shows the average strength of the Fourier coefficients of log( (x)/m(x)), with q(x) a multipolar synthetic density for L-alanine at 23 K, and two different prior-prejudice distributions mix). It is apparent that the exponential needed to modulate the uniform prior still has Fourier coefficients larger than 0.01 past the experimental resolution limit of 0.463 A. Any attempt at fitting the corresponding experimental structure factor amplitudes by modulation of the uniform prior-prejudice distribution will therefore create series termination ripples in the resulting MaxEnt distribution. 

Explain the differences between dispersive and distributive m being. Why does dispersive mixing rely on shearing processes, while distributive mixing relies on iteratively folding the polymer melt back on itself ... 

The cavity transfer mixer (CTM) is a distributive mixing device used as an add-on unit to extruders the barrel and screw have hemispheres cut out of their surfaces to give an overlap of half a pitch. 

Figure 8.1 Distributive mixing mechanism for the baker s fold process a) stretch and fold method, and b) stretch, cut, and stack method...

Other entropy types have been developed to determine the mixing level in systems, including Shannon entropy and Renyi entropy. Shannon entropy has been used to show distributive mixing levels in color mixing experiments [18,19], while Renyi entropy has been used to show a more rigorous analysis of distributive mixing [20, 21]. The reader is referred to the references as these types of entropies are beyond the scope of this chapter. 

Wang, W., Manas-Zloczower, I., and Kaufman, M., Characterization of Distributive Mixing in Polymer Processing Equipment using Renyi Entropies, Int. Polym. Process., 16, 315 (2001)... 

Furches, B. and Bozzelli, ]., Screw Design Efficiency in Color Distributive Mixing with ABS Resins, SPE ANTEC Tech. Papers, 33, 6 (1987)... 

Although the full history of this screw is unknown, the mixing pins appeared to have been added to the screw after the screw failed to mix and homogenize the extrudate. Pin mixers have been retrofitted to screws for many years as a way to improve the distributive mixing for an extruder. Here the pin mixers would distribute the solid polymer fragments evenly in the extrudate, hut the mixers lacked the ability to trap and disperse them. Pin mixers were clearly the wrong type of mixer to use for this application. Instead, a dispersive mixer such as a Maddock-style mixer would be preferred see Section 8.5.1. 

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