Polymers, periodic conclusions

Unfortunately, the pump-back test after the well shut-in period showed severe polymer loss (Fig. 17). The cause of the low viscosities in the pump-back samples was attributed primarily to bacterial degradation of the polymer. This conclusion was supported by the high levels of bacteria (10 to 10 bacteria/cm ) in the produced samples. Polymer adsorption on the reservoir rock was not a likely cause of the polymer loss because 230,600 bbl [36.66 x 10 m ] of polymer solution had passed through the fracture, and all adsorption sites should have been satisfied. Iron levels were still high (25 to 100 ppm) despite use of a stainless steel rod pump and... 

To evaluate the effectiveness of H2S as a biocide in the Tensleep reservoir, 11,200 bbl [1.78X 10 m3] of polymer solution was injected into Well 74. Measurable but not serious plugging was observed on the fracture face. Every precaution was taken to eliminate oxygen from the injection plant facilities (oxygen levels just upstream of the wellhead were always < 10 ppb). Because tritium was used as a tracer in the second test, cobalt-57 was used as the tracer in this test. After the 2-week well shut-in period, polymer levels in the produced fluids were only about one-half of what was expected from the tracer results (Fig. 18). All of the available evidence led to the conclusion that the H2S in FIB did not prevent bacterial degradation of the polymer. This conclusion was supported by the fact that high levels of aerobic, general facultative-aerobic, and sulfate-reducing bacteria were found in the produced solutions. It was not apparent why bacterial control was successful in the laboratory and not in the field. 

Bubbles are formed instantaneously. This conclusion made in [33] is based on estimates taken from earlier works [37]. As seen from the above cited works by S. E. Sosin et al., this is not always true viscoelastic liquids under triaxial stretching stress are not destroyed instantly. The existence of an induction period may produce a considerable effect on foam growth kinetics upon free foaming, when pressure is lowered instantaneously from P > Pcr to P < Pcr in a melt with dissolved gas. However, it would appear that microfaults in polymer melts, which are caused by factors... 

The chains of some polymer molecules are not fully extended the identity-periods leave no doubt of that. By rotation round the single bonds the chains are crumpled and shortened. The magnitude of the identity-period may by itself indicate the geometry of the chain, but more probably it will not be possible to draw unambiguous conclusions without the aid of further stereochemical considerations. Examples... 

D-xylose on hydrolysis with dilute nitric acid. Percival and Chanda7 isolated a xylan from the same plant. They found that the methylated xylan produced on hydrolysis 2-methyl-D-xylose, 2,3-dimethyl-D-xylose, 2,4-dimethyl-D-xylose and 2,3,4-trimethyl-D-xylose. From this and from the results of periodate oxidation, Percival and Chanda considered that the polysaccharide contains 1 — 3 and 1 —> 4 linkages with a non-reducing endgroup (yielding the 2,3,4-trimethyl-D-xylose) for every 20-21 D-xylose units. They considered that this xylan was not a mixture of 1 —> 3 and 1 —> 4 linked polysaccharides because careful fractionation of its diacetate and dimethyl ether failed to establish any polymer heterogeneity. Barry, Dillon, Hawkins and O Colla74 confirmed the conclusion of Percival and Chanda. 

Yamashita [128] reports that the kinetics of polymerization of 1,3-dioxolane initiated by BF3. Et2 O are quite complex and that initiation is not a simple reaction. In 1973 Rozenberg et al. [130] reported a kinetic study of such a polymerization in CHjClj solution. They e ain found an induction period, but this time stated that the acceleration is the result of the autocatalytic action of the macromolecules formed. Their conclusions are based (i) on the relationship of the rate coefficients of BF3. Et2 0 reactions with cyclic monomer or with polymer chain and (ii) on the decrease of the induction period on addition of polymer or methylal to a polymerizing mixture. The mechanism of initiation suggested is... 

Conspicuously, different from all other polymers is the antifreeze, which at all freezing rates partitioned equally between ice and the imfrozen solution i.e., it appears to be equally "soluble" in ice and water. This result confirms that the molecule can interact with the ice phase over a kinetically long period of time. It is not known from these results whether the mechanism is a permanent adsorption this would require supporting evidence from other physical measurement techniques. All the other solutes show a rate-dependent mechanism of partitioning, presumably dominated by the diffusion rates of the molecules. LEG and FVA may exhibit some nonkinetic partitioning properties, but this has not been conclusively proven. 

Similar conclusions have been reached on the basis of studies with TiClj and amines (69). These catalysts polymerize propylene at a slow rate to highly isotactic polymers. The active site was long lived because polypropylene molecular weight increased with polymerization time over a long period. Mechanism studies (70) with the TiClj-Et N and Ziegler catalysts indicate a close resemblance and support the view that both catalyst types operate by propagation at a transition metal-carbon bond. 

A number of polymers studied by Dulmage and Contois in then-pioneering paper have not been included in Table 2, owing to lack of space. Their results support the foregoing conclusions, since they showed that a low modulus was invariably associated with a contracted fibre identity period. 

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