Viscosity reduction factor

What is common in Figures 13.5-13.8 is that the viscosity of a neat polymer, LDPE or PS, is decreased considerably by the solubilization of an FC blowing agent. It would be of practical interest to determine the extent of viscosity reduction of a molten polymer by a solubilized gaseous component. For this, let us define a viscosity reduction factor by (Han and Ma 1983a, 1983b)... 

Table 13.1 Summary of the viscosity reduction factor Op for mixtures of Rexene 143 and EC blowing agent...

Table 13.3 Average value of viscosity reduction factor Ouf for mixtures of Rexene 143 or Styron 678 with FC blowing agent.

Assume the PS and mixture PS+R22 can be modeled as an inelastic, non-Newtonian fluid. Rate-controlled viscosity measurements have been conducted by Han [2] on numerous systems of polymers and blowing agents. He chose to translate the degree of plasticization observed into a viscosity reduction factor (VRF) defined as follows ... 

Select Ihe next larger orifice size, or an M" orifice with 360 sq in. orifice area. (This should be about 20% greater than the calculated area to allow lor reduction of capacity due to Ihe viscosity correction factor "Ku")... 

The free-volume concept was applied most widely in the theory of viscoelastic properties of polymers developed by Williams, Landel and Ferry (WLF theory), presented in detail in12. According to WLF theory, the changes in liquid viscosity with frequency and temperature from glass temperature T% to T may be plotted on a single master curve by using the reduction factor... 

Figure I 1.7. Variation of viscoelastic scaling factors with gas content for PS-C02 and PDMS-C02 systems. Lower scaling factor values for PS-C02 system, compared with PDMS-C02 system, are due to the closer proximity of the experimental temperatures to Tg of the pure polymer. The top curve displaying results for iso-free volume dilution of high-Mw polystyrene by low-Af polystyrene represents the effect on viscosity of volumetric dilution of high-Mw chains. Viscosity reductions for polymer-gas systems are significantly lower than the iso-free volume dilution curve, indicating that viscosity reduction is primarily due to free volume contributed by dissolved gas.

A modified version of the free-volume theory is used to calculate the viscoelastic scaling factor or the Newtonian viscosity reduction where the fractional free volumes of pure polymer and polymer-SCF mixtures are determined from thermodynamic data and equation-of-state models. The significance of the combined EOS and free-volume theory is that the viscoelastic scaling factor can be predicted accurately without requiring any mixture rheological data. 

Crosslinked polymer-like bulk gel used in water shut-off has very poor flowability the viscosity is very high (>10,000 mPa s). Uncrosslinked polymer is used to increase water viscosity. A movable gel is used in between it has the intermediate viscosity, and more importantly, it can flow under some pressure gradient. Colloidal dispersion gel (CDG) is a typical gel used in these situations. The mechanisms of a movable gel are (1) it has high viscosity to improve mobility ratio like an uncrosslinked polymer solution (2) it has a high resistance factor and high residual permeability reduction factor and (3) it has viscoelasticity so that the remaining oil in the rocks can be further reduced. 

Resistance is related to mobility, which includes the effects of both permeability reduction and viscosity increase. Obviously, the viscosity effect is not included in the residual resistance factor defined in Eq. 5.41 because water viscosity is used before and after polymer flow. Such a name convention is confusing. Therefore, we suggest the terms permeability reduction factor and residual permeability reduction factor be used. If the process were considered reversible, there would be no need for the term of residual permeability reduction factor. To include both permeability reduction and viscosity increase, we define another parameter, resistance factor (F,) ... 

In UTCHEM, the viscosity of the aqueous phase that contains the polymer is multiplied by the value of the polymer permeability reduction factor, F r, to account for the mobility reduction. In other words, water relative permeability, km, is reduced, whereas oil relative permeability, k , is sometimes considered almost unchanged. The reason is that polymer is not soluble in oU, so it will not reduce effective oil permeability. The mechanism of disproportionate permeability reduction is widely used in gel treatment for water shut-off. Many polymers and gels can reduce permeability to water more than to oil or gas. 

In ASP flooding, alkaline, surfactant, and polymer have different effects on relative permeabilities. Table 13.2 shows our attempt to summarize these effects compared with waterflood. From Table 13.2, we can see that the effect of alkaline flood in terms of emulsification is similar to the polymer effect, whereas its effect in terms of IFT is similar to the surfactant effect. Less rigorously, we may say that only polymer reduces k, and only surfactant reduces IFT. In ASP flooding, the viscosity of the aqueous phase that contains the polymer is multiplied by the polymer permeability reduction factor in polymer flooding and the residual permeability reduction factor in postpolymer water-flooding to consider the polymer-reduced k effect. Then we can use the k curves (water, oil, and microemulsion) from surfactant flooding or alkaline-surfactant flooding experiments without polymer. 

Ye and Peng (1995) measured ASP solution/oil relative permeabilities based on the preceding principle. They first conducted a core flood test using an ASP solution and calculated the Darcy viscosity for the solution, which included the polymer permeability reduction factor. Then they conducted ASP/... 

Equation (2.17) allows us to make a number of conclusions. So, at the conditions mentioned previously, conservation increase, that is, initial nanoparticles aggregation intensification, results to nanocomposite melt viscosity reduction, whereas enhancement, i.e., increasing the nanoparticles degree of surface roughness, raises the melt viscosity. At = 2.0, i.e., the nanofiller particles have a smooth surface, the melt viscosity for the matrix polymer and the nanocomposite will be equal. It is interesting that the extrapolation of the MFl dependence, obtained experimentally, and for the one calculated using Eq. (2.19), values give the value of MFl = 0.602 g/10 min at d = 2.0, that is practically equal to the experimental value of MFI = 0.622 g/10 min. The indicated factors, critical ones for nanocomposites, are not taken into consideration in continuous treatment of melt viscosity for polymer composites (Eq. (2.8)). 

Thus, the fractal analysis methods were used above for treatment of comb-like poly(sodiumoxi) methylsylseskvioxanes behavior in solution. It has been shown that the intrinsic viscosity reduction at transition from a linear analog to a branched one is due to the sole factor, namely, to a macromolecule connectivity degree enhancement, characterized by spectral dimension. This conclusion is confirmed by a good correspondence of the experimental and calculated according to Mark-Kuhn-Houwink equation fiactal variant intrinsic viscosity values. It has been shown that qualitative transition of the stmcture of branched polymer macromolecular coil from a good solvent to 0-solvent can be reached by a solvent change. 

The Eq. (57) allows making the following conclusion. The increase of both /j, and (if the value is used) results in melt viscosity reduction. The indicated factors, critical for oiganoclay, are not taken into account again in continuous melt viscosity treatment for polymer composites (the Eq. (42)). 

Table 18.7 lists viscosity reductions measured due to the presence of an SCF in the polymer. Because few researchers have reported the zero shear rate viscosity for both the pure polymer melt and the SCF-swollen melt, an experimental shift factor cannot usually be estimated from the data. Instead, Table 18.7 lists the ratio of viscosity measured in the presence of SCF diluent (rjoii) to the viscosity measured in the absence of diluent (rj), at some reference conditions. Unless otherwise specified, the reference state has no SCF, and has the same temperature as the experimental state. The pressure for the reference state, and dynamic characterization conditions (e.g., constant stress, cr, or constant y) are also specified in Table 18.7. 

Pseudomonas - mo-n9s [NL, fr. pseud- -h monad-, monos monad] (1903) n. A generic class of aerobic, mesophilic bacterium capable of releasing a variety of enzymes, including ceUulose-decomposing cellulose enzymes these enzymes are a factor in viscosity reduction of latex paints modified with ceUulosic thickener, and may... 

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