Apparent polymer

Figure B8.2.1 shows the fluorescence spectra of DIPHANT in a polybutadiene matrix. The h/lu ratios turned out to be significantly lower than in solution, which means that the internal rotation of the probe is restricted in such a relatively rigid polymer matrix. The fluorescence intensity of the monomer is approximately constant at temperatures ranging from —100 to —20 °C, which indicates that the probe motions are hindered, and then decreases with a concomitant increase in the excimer fluorescence. The onset of probe mobility, detected by the start of the decrease in the monomer intensity and lifetime occurs at about —20 °C, i.e. well above the low-frequency static reference temperature Tg (glass transition temperature) of the polybutadiene sample, which is —91 °C (measured at 1 Hz). This temperature shift shows the strong dependence of the apparent polymer flexibility on the characteristic frequency of the experimental technique. This frequency is the reciprocal of the monomer excited-state...

Well-defined crystalline compounds MnX2- L for n = 2, 1 and < 1 also are described.227,230,232,237 Most are apparently polymers of types (8) and (13), although tetrahedral [MnX2L2] species may eventually be identified. A different polymer, with cis unidentate ethylacetates, at 2.17 and 2.24 A, has been identified238 in [Mn(P02Cl2)2(ethylacetate)2]. 

No reaction is observed between the benzyl or allyl halides and the stannylenes, even in warm benzene in which these derivatives are apparently polymers. However, these ethers can be prepared in good yields in refluxing benzene in the presence of catalytic quantities of tetraalkylammonium halides and this is... 

Apparently, polymer conformation plays an important role in flocculation caused predominantly by bridging. This effect of polymer conformation on the dispersion properties has been confirmed by many observations where significantly different dispersion behavior is obtained with identical adsorption density and electrostatic property. There have been substantial efforts both theoretically and experimentally to develop relationships between the stability and the polymer conformation... 

Table VII data show that Polymer 9 was an unusual polymer. This is seen in its very high modulus, low extensibility at break, high T value, and insolubility even in DMF. Apparently Polymer 9 is an unusually high molecular weight polymer which we feel resulted from the use of (intermediate) acid numer PTAd.

Anyway, bridging by adsorbed polymers will often depend on the history of the system. Consider a dispersion of small solid particles that tend to aggregate. To stabilize the suspension, an adsorbing polymer is added that can give a maximum surface excess Tpiateau of 6 mg m-2. If the specific particle surface area A is lm2 per ml and 3 mg of a suitable surfactant polymer is added per ml, a r value of at most 3 mg per m2 can result. This value is on the low side, but the particles are nevertheless stabilized apparently, polymer chains stick out far enough into the solvent to cause steric repulsion. Assume now that to 1 ml of the suspension 6 mg of polymer is added and that subsequently 1 ml of suspension without polymer is added. 

The liquid crystals, in fact, meet the above requirements large molecular length, linear molecular configuration and with polar terminals. Unfortunately, low molecular mass liquid crystals have difficulty in maintaining the non-center symmetry after electrical polarization. Moreover, it is difficult to process the low molecular mass liquid crystal materials. Apparently, polymers are good candidates in these respects. 

The initial values of the dynamic strength of the coated samples are seen (Fig. 3.43) to be higher than those without the coatings. Apparently, polymer coatings hamper access of hostile media to the metal and contribute to... 

Selective flocculation. Suppose X23 is positive but now the dispersion medium is adjusted to be a worse than 0-solvent for, say, polymer 2 (Xi2>2 but Xi3 < 2)- Homoflocculation of the particles coated by polymer 2 will ensue. Provided that xii is not excessively large, heteroflocculation would be expected to be absent. This implies that it should be possible under such conditions to flocculate selectively one species of sterically stabilized particles in a mixed dispersion. Apparently polymer coated particles are able to discriminate between self and not-selF when undergoing Brownian collisions in such dispersion media, coagulation only occurring between particles of the same type. Of course, if the dispersion medium were made a worse than 0-solvent for both polymers (xi2. Xi3>tX both 2-2 and 3-3 homoflocculation would occur. Heteroflocculation would only be possible if... 

B, Immersed in water after casting from the polymer solution and keeping in air at 20°C for 20 min (apparent polymer concentration before immersion, 8.6%). 

This parameter is also called the apparent polymer-polymer interaction parameter [43]. 

Although excluded-volume effects are well-accepted in polymer chromatography, the preceding arguments are not without controversy in the petroleum literature because of the way that the apparent polymer viscosity in porous media was determined. In our work, we simply report the resistance factor (i.e., the brine mobility before polymer injection divided by the polymer-solution mobility). This is a well-defined parameter that derives directly from the Darcy equation and measurements of pressure drops and flow rates. Advocates of the depletion-layer effects use a different method to determine apparent polymer viscosity in porous media. Specifically, they flush water through the core after polymer injection to determine the permeability reduction or residual resistance factor. The resistance factor during polymer injection is then divided by the residual resistance factor to determine the apparent polymer viscosity in porous media. Unfortunately, several experimental factors can lead to incorrect measurement of high residual resistance factors, which, in turn, lead to calculation of unexpectedly low apparent polymer viscosities in porous media. 

For the 750 ppm solution, the simulator used a resistance factor of 28.63 to yield a 22.0 cp apparent polymer viscosity for the prediction of the flood performance. This concentration yielded a favorable mobility ratio of 0.26 at residual oil saturation. The simulator predicted that the polymer flood would recover 3,042 MBO or 8.0 percent... 

Leung, J., Srinivasan, S., and Huh, C. 2010. Accounting for Heterogeneity In Scale-Up of Apparent Polymer Viscosity for Field Scale Application. Paper SPE 129798 presented at the SPE Improved Pil Recovery Symposium, Tulsa, 24-28 April. DPI 10.2118/129798-MS. 

The previous swelling equations are valid for molecularly homogeneous systems. However, some polymer gels contain pores or voids which contribute to the volume of the system. Such is the case with many porous ion-exchange resins or porous superabsorbent particles. Therefore, the measured polymer volume fraction in the swollen gel, )2,app> s larger than the actual polymer volume fraction in the swollen polymer, U2 s. The apparent polymer volume fraction in a porous system may be... 

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