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Copolymer solution viscosity

Solutions of starch-acrylamide, graft copolymers, were prepared by J. J. Meister and the solution viscosity was researched with the goal to prepare highly viscous solutions He was able to prove, that graft copolymers also age. However, the data have another feature not found in the viscosities of the PAAm-solutions. That is, that graft-copolymer solution viscosity increases between 24 and 48 hours. After this a typical viscosity decrease can be observed as was mentioned earlier. [Pg.170]

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. [Pg.493]

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. [Pg.70]

Membrane stmcture is a function of the materials used (polymer composition, molecular weight distribution, solvent system, etc) and the mode of preparation (solution viscosity, evaporation time, humidity, etc). Commonly used polymers include cellulose acetates, polyamides, polysulfones, dynels (vinyl chloride-acrylonitrile copolymers) and poly(vinyhdene fluoride). [Pg.294]

The presence of flexible PEO and PPO blocks increases the viscosities of block copolymer solutions, this tendency is manifesting itself the stronger the greater is the PEO and PPO content in block copolymers. [Pg.132]

Viscosimetric studies of organotin copolymer solutions allow the changes in the shape of the macromolecules to be followed as a function of the electrostatic charge. From the plot of the intrinsic viscosity of copolymers in DMFA solution against the degree of dilution it is seen that increasing dilution results in a rise of viscosity, probably due to an extension of macromolecular chains accompanied by conformational transformations. Naturally, this rise in viscosity with dilution cannot proceed infinitely since a coiled chain cannot be extended more than a completely extended chain conformation, due to intramolecular repulsion. [Pg.124]

Predictions of the Evolution with Time of the Viscosity of Acrylamine—Acrylic Acid Copolymer Solutions... [Pg.116]

Comparison of the limiting viscosity numbers determined in deionized water with those determined in 1 molar sodium nitrate shows a 20 per cent decrease in copolymer intrinsic viscosity in the saline solution. These results are consistent with previous studies using aqueous saline solutions as theta solvents for 2-propenamide polymers(47) Degree of hydrolysis controls the value of limiting viscosity number for the hydrolyzed copolymers in distilled water. [Pg.187]

Solutions containing 0.15 g/dL polymer and between 0 and 0.342 molar sodium chloride or between 0 and 2.49 x 10 molar calcium chloride show declines in viscosity as salt content increases. Solution viscosity of nonionic copolymers declines, at most,... [Pg.187]

Solutions of hydrolyzed copolymer lose viscosity exponentially as electrolyte concentration in the solution increases. [Pg.187]

Figure 7. Effect of sodium chloride concentration on the viscosity of hydrolyzed poly(starch g-(2 propenamide)) copolymer solutions. Figure 7. Effect of sodium chloride concentration on the viscosity of hydrolyzed poly(starch g-(2 propenamide)) copolymer solutions.
Effective viscosity as a function of shear rate for 0.15 g/dL of copolymer 5 in distilled water is given in Figure 15 The Ostwald-DeWaele exponent for copolymer solutions is greater than that of matching hydrolyzed copolymer solutions at a given concentration. Thus, copolymer molecules are less compactable in solution than are their hydrolyzed derivatives, and pseudoplasticity of polymer solutions increases upon hydrolysis. [Pg.192]

Viscosity of copolymer solutions decreases by, at most, 3 percent when electrolyte concentration changes from 0 to 0.342 M sodium chloride or 2.45 x 10 M calcium chloride. Viscosity of hydrolyzed polymer solutions decreases exponentially with increasing electrolyte concentration in water. [Pg.204]

The comparison of the 2D plot of a graft copolymer with the 2D plot of the precursor PEO shows clearly that the graft copolymer sample does not contain any free PEO. This result was also confirmed by MALDI-TOF mass spectrometry. Next to the requirement of being PEO free, the PEO-g-PVA copolymers showed a good combination of film-forming properties, a fast dissolution, and a low solution viscosity in water. The phase separated morphology, as demonstrated by TEM, DSC, DMTA, and WAXS experiments, provided the PEO-g-PVA copolymers with relatively constant mechanical properties. [Pg.403]

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. [Pg.105]

Here kH is the Huggins coefficient. The intrinsic viscosity decreases and the Huggins coefficient increases, as micelles become smaller. On micellization, ijsp/c has been observed to increase for some systems but to decrease for others, and unfortunately there are no firm rules governing which case will prevail for a given block copolymer solution. The viscosities of polymer solutions are measured in capillary flow viscometers, which are described in detail by Macosko (1994). [Pg.17]

Redistribution and Polymer Structure. The structure of DMP-DPP copolymers is probably determined by the relative rates of the polymerization reaction and the monomer-polymer redistribution reaction. In the DMP-DPP system, structure may be predicted simply by observing the effect on solution viscosity of the addition of one of the monomers to the growing polymer derived from the other monomer. When DPP is added to a DMP reaction mixture, the solution viscosity drops immediately almost to the level of the solvent, as redistribution converts the polymer already formed to a mixture of low oligomers ... [Pg.249]

Continued oxidation of this mixture should yield a random copolymer, which was the result when method b was used. When DMP was added to growing DPP polymer, the solution viscosity did not drop but continued to increase at a faster rate than before the reactive DMP monomer was added. If redistribution between DMP and DPP homopolymer occurred, the rate was small compared with the rate of polymer growth. This at least allows the possibility of producing block copolymers, the result obtained when procedure c was followed. The effect of varia-... [Pg.249]

Procedure 3 Addition of MPP to Polymerizing DMP. Procedure 1 was followed with only the DMP initially present. After two hours, the MPP was added, causing a prolonged decrease in solution viscosity oxidation was continued for three hours after MPP addition. The copolymer was obtained in 92% yield, with an intrinsic viscosity of 0.58 dl/g. [Pg.251]

The catalyst was prepared as in the previous examples, 9.9 grams of DPP was added, and oxidation continued at 60° C the volume was maintained about constant by periodic addition of benzene. After four hours, 7.3 grams of DMP was added, causing a sharp decrease in solution viscosity. Oxidation was continued for four hours after addition of the DMP. The copolymer, obtained in 8135 yield, had an intrinsic viscosity of 0.37 dl/g. [Pg.262]

Procedure 5 Addition of DPP to Growing MPP at 60° C. The method of procedure 4 was followed with only the MPP initially present. The DPP was added after four hours. No decrease in solution viscosity was observed. Oxidation was continued for three hours, and the copolymer was obtained in 88% yield it had an intrinsic viscosity of 0.35 dl/ g. [Pg.262]

Sequential Oxidation of DMP and DPP. The usual approach to formation of block copolymers is by the sequential polymerization of two or more monomers or by linking together preformed homopolymer blocks. In view of the importance of the redistribution process in the oxidative coupling of phenols there can be no assurance that successive polymerization of two phenols will yield block copolymers under any conditions. It is certain, however, that block copolymers can be formed only if the conditions are such that polymerization of the second monomer is much faster than redistribution of the added monomer with the polymer previously formed from the first. The extent of redistribution is followed conveniently by noting the effect of added monomer on solution viscosity, as indicated by the efflux time from a calibrated pipet. [Pg.448]

Intrinsic viscosity serves as a measure ofthe hydrodynamic volume of a single particle in the solution under study. Viscosity of micellar solutions can be measured using an Ubbelohde viscometer at a given temperature (AstaLeva et al., 1993 Pandya et al., 1993 Zhou and Chu, 1994). The temperature ofthe thermostatted bath is usually controlled within 0(D2o obtain an accurate measurement. Aftera desired temperature is set, each solution should be temperature-equilibrated for at least 20 min before viscosity measurement. An average low time is taken for several consecutive measurements on the same copolymer solution to calculate the viscosity value. [Pg.344]

Solubilization oftropicamide, a poorly water-soluble mydriatic/cycloplegicdrug, by poloxamers or Pluronics was studied (Saettone et al., 1988). The polymers evaluated as solubilizers for the drug included L-64, P-65, F-68, P-75, F-77, P-84, P-85, F-87, F-88, and F-127. The authors measured a range of physicochemical properties, such as solubility oftropicamide in polymer solutions, partition coefLcient of the drug between isopropyl myristate and copolymer solutions, critical micelle concentration of the copolymers, and viscosity of the copolymeric solutions containing tropicamide. [Pg.353]

Next, we present experimental evidence for the electric-field-induced decrease of Todt in a block copolymer. Because of the high melt viscosities, temperatures close to the decomposition temperature and extremely high electric field strengths are required to achieve a measurable effect. In recent studies, we have demonstrated that concentrated block copolymer solutions in a neutral solvent act like a melt, thereby effectively circumventing the above-mentioned limitations [31, 57, 70],... [Pg.24]

The first report is available from Shen et al. who studied the preparation of BR/IR block copolymers by sequential polymerization of BD and IP [92]. Shen et al. found that the polymerization of the second monomer batch resulted in an increase of solution viscosity by 100%. The viscosity increase was considered as strong evidence in favor of block copolymer formation. Further evidence came from stress strain measurements in which the respective BD/IP block copolymers were compared with blends of BR and IR (at the same molar masses). It was found that the block copolymer exhibited higher elongation at break and higher tensile strength. Unfortunately, Mn data were not provided. Therefore, these results are not fully relevant regarding requirement No. 5 for a living polymerization. [Pg.122]

This finds some support in a comparison of solution viscosities with polymerization time of a few isolated cases of Diels-Alder polymerization reactions. In the polymerization of 2,5-dimethylene-3,4-diphenylcyclo-pentadieneone with N.N -hexamethylene-fo s-maleimide, the reduced viscosity of the polymer increases from 0.97 after 1 hr to 1.20 after six hours (7). It is necessary to assume that the rate controlling step in this reaction is neither the formation of the initial adduct nor the loss of carbon monoxide. The inherent viscosity of the l,6-6is-(cyclopenta-dienyl)hexane-quinone copolymer increases from 0.10 after sixteen hours to 0.12 after twenty four hours reaction time in refluxing benzene (14). [Pg.56]

Solution Viscosity. The intrinsic viscosities [77] of the copolymers were measured for solutions in dry toluene at 25 °C. by dilution in an Ubbelohde suspended-level viscometer. Conventional plots of rj/c (18) and log (1 + r )/c (29) were found to be nonlinear for all copolymers where 77 is the specific viscosity. To get accurate values of the intrinsic viscosities and of the Huggins constants h and k2, triple plots were drawn as recommended by Heller (16). These gave the intercept 1/[iy], and fci and were determined directly from the initial slopes of the plots... [Pg.524]

For a specific polymer, critical concentrations and temperatures depend on the solvent. In Fig. 15.42b the concentration condition has already been illustrated on the basis of solution viscosity. Much work has been reported on PpPTA in sulphuric acid and of PpPBA in dimethylacetamide/lithium chloride. Besides, Boerstoel (1998), Boerstoel et al. (2001) and Northolt et al. (2001) studied liquid crystalline solutions of cellulose in phosphoric acid. In Fig. 16.27 a simple example of the phase behaviour of PpPTA in sulphuric acid (see also Chap. 19) is shown (Dobb, 1985). In this figure it is indicated that a direct transition from mesophase to isotropic liquid may exist. This is not necessarily true, however, as it has been found that in some solutions the nematic mesophase and isotropic phase coexist in equilibrium (Collyer, 1996). Such behaviour was found by Aharoni (1980) for a 50/50 copolymer of //-hexyl and n-propylisocyanate in toluene and shown in Fig. 16.28. Clearing temperatures for PpPTA (Twaron or Kevlar , PIPD (or M5), PABI and cellulose in their respective solvents are illustrated in Fig. 16.29. The rigidity of the polymer chains increases in the order of cellulose, PpPTA, PIPD. The very rigid PIPD has a LC phase already at very low concentrations. Even cellulose, which, in principle, is able to freely rotate around the ether bond, forms a LC phase at relatively low concentrations. [Pg.635]


See other pages where Copolymer solution viscosity is mentioned: [Pg.192]    [Pg.103]    [Pg.116]    [Pg.129]    [Pg.192]    [Pg.36]    [Pg.627]    [Pg.22]    [Pg.69]    [Pg.70]    [Pg.72]    [Pg.333]    [Pg.419]    [Pg.6]    [Pg.185]    [Pg.263]    [Pg.250]    [Pg.267]   
See also in sourсe #XX -- [ Pg.103 ]

See also in sourсe #XX -- [ Pg.103 ]




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