Polymer viscosity reduction

Zitha, P.L.J. 2001. Prediction of Polymer Viscosity Reduction in Pores Using an Exact Depletion Profile. Paper SPE 68981 presented at the SPE European Formation Damage Conference, The Hague, 21-22 May. DPI 10.2118/68981-MS. 

Among the techniques employed to estimate the average molecular weight distribution of polymers are end-group analysis, dilute solution viscosity, reduction in vapor pressure, ebuUiometry, cryoscopy, vapor pressure osmometry, fractionation, hplc, phase distribution chromatography, field flow fractionation, and gel-permeation chromatography (gpc). For routine analysis of SBR polymers, gpc is widely accepted. Table 1 lists a number of physical properties of SBR (random) compared to natural mbber, solution polybutadiene, and SB block copolymer. 

One of the most attractive features of TLCPs is their ability to alter the rheology of bulk thermoplastic polymers. Most reports in the academic literature are concerned with viscosity reduction. For example, Siegmann et al. [1] observed a steep viscosity drop when a TLCP... 

They may also act as reactive super plasticisers to increase rubber flow while increasing the mechanical properties of the rubber. Viscosity reduction or polymer solvation and higher filler loading can be accomplished with less plasticiser. Flow is achieved through molecular rearrangement and not average molecular weight reduction of the rubber. 

It is well known that addition of neutral salts to polymer solutions reduces the overall dimensions of polymer chains (the salting-out effect) [43, 44]. In general, the reduction in chain dimensions is reflected in the polymer viscosity. An example of salt effects on water soluble polymer with non-ionic characters has been reported in the literature where the precipitation temperature and the viscosity of polyethylene oxide (PEO) were measured to interpret the unusual... 

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.

An important difference between the PS-gas systems (Kwag et al., 1999) and the PDMS-C02 system (Gerhardt et al., 1997) is that the viscosity measurements of the PS-gas systems are conducted at temperatures within 75 °C of T of PS, whereas the PDMS-C02 measurements were performed nearly 200 °C above Tg of PDMS. The difference between these two thermal regimes leads to several differences in the observed rheological behavior. The viscosity reductions relative to the pure polymer are much greater for PS-gas systems than for PDMS-C02 systems at similar dissolved gas compositions, and the dependence of ac on temperature is much more pronounced for the PS-gas systems. These trends are consistent with the observations of Gerhardt et al. (1997, 1998) that the effect of dissolved gas on polymer melt viscosity occurs primarily through a free-volume mechanism. 

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. 

Dispersing agent Improved dispersion of pigments or fillers, viscosity reduction, increase of filler content, better end properties Pretreatment of fillers or pigments or as a polymer additive... 

Solvents in paint or a coating serve multiple purposes. These include solubilization of resins and other ingredients, wetting, viscosity reduction, adhesion promotion, and gloss enhancement. Initially, the resin or polymer is dissolved in the solvent to form a continuous phase. 

Fig. 7 shows the CO2 induced viscosity reductions of PP and PS polymers. The viscosities of the polymer/CO2 mixtures were measured by a capillary rheometer equipped with a foaming extruder. As can be seen in Fig. 7, the viscosity of PS was reduced by 40% by dissolving CO2 3.5 wt%o and that of PP was reduced by 25 /o. The solid lines in Fig. 7 represent the estimates of the aforementioned models. 

Here, the constants, K (mPa s ) and n (dimensionless), are the consistency index and the exponent, respectively Up is the Darcy velocity (m/s) of the polymer-containing water phase k is the average permeability in m is the water phase relative permeability S is water satnration (fraction) is porosity (fraction) is the viscosity at infinite shear rate and C is an empirical constant. Note that Eq. 5.23 is made more general by including the nonunit water saturation, Sw, and the water relative permeability, k,w, as was done previously by Hirasaki and Pope (1974). To consider the polymer permeability reduction fector Ffa explicitly (to be discussed later), we should divide the permeability k by Ekr, and n, is substitnted for Up. Then Eq. 5.23 becomes... 

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. 

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