Intrinsic viscosity measuring

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

When viscometric measurements of ECH homopolymer fractions were obtained in benzene, the nonperturbed dimensions and the steric hindrance parameter were calculated (24). Erom experimental data collected on polymer solubiUty in 39 solvents and intrinsic viscosity measurements in 19 solvents, Hansen (30) model parameters, 5 and 5 could be deterrnined (24). The notation 5 symbolizes the dispersion forces or nonpolar interactions 5 a representation of the sum of 8 (polar interactions) and 8 (hydrogen bonding interactions). The homopolymer is soluble in solvents that have solubility parameters 6 > 7.9, 6 > 5.5, and 0.2 < <5.0 (31). SolubiUty was also determined using a method (32) in which 8 represents the solubiUty parameter... 

Intrinsic viscosity measurements revealed a conformational transition upon heating from 26 to 40 °C, while the UV absorbance of the solution was insensitive to the change. The entropy parameters for PA were also discussed in light of the Flory-Krigbaum correlation between the second virial coefficient and theta temper-... 

Membrane osmometry, vapor pressure osmometry, gel permeation chromatography, light scattering, and intrinsic viscosity measurements have been used to... 

Intrinsic Viscosity Measurements were made by standard techniques in dimethyl formamide (DMF) at 30 C. Weight average molecular weights were calculated from the following relationship ... 

Hydrodynamic Properties of Gelatin -Studies from Intrinsic Viscosity Measurements... 

Due to the lack of data on the uniformity of intrinsic viscosity measurements in the gelatin/water system, clearly shows a decrease in "a" with temperature, and this Mw is 333,000g/ mol. 

Perturbed and unperturbed polymer dimensions deduced from intrinsic viscosity measurements, according to procedures which will be discussed later, are given in Table XXXIX of Chapter XIV. The... 

The results of intrinsic viscosity measurements for four polymer-solvent systems made at the -temperature of each are shown in Fig. 141. The four systems and their -temperatures are polyisobutylene in benzene at 24°C, polystyrene in cyclohexane at 34°C, poly-(di-methylsiloxane) in methyl ethyl ketone at 20°C, and cellulose tricapry-late in 7-phenylpropyl alcohol at 48°C. In each case a series of poly-... 

The demonstration of proportionality of the intrinsic viscosity measured at the 0-point to over wide ranges in molecular weight offers solid support for the basic premise of the simple interpretation presented in the preceding section, namely, that the intrinsic viscosity is proportional to the cube of a linear dimension such as This conclusion rests, of course, on the premise that at the 0-point... 

In order to achieve a quantitative separation of the factors responsible for the temperature coefficient of the intrinsic viscosity, K should first be established as a function of temperature by carrying out measurements in -solvents having s covering the temperature range of interest. The expansion factor may then be obtained from the intrinsic viscosity measured at the temperature T in the given solvent. If Cm occurring in Eq. (10) were independent of the temperature, — should then plot linearly with 1/T, However,... 

Figure 12 were superimposable on those for detector 2. Therefore, when the plot shown in Figure 14 is linear over the range of compositions involved in the sample, then (according to equations (1-4) ) the composition of the sample is the same at each retention volume. If the variation with retention volume is negligible the copolymer can then possibly be treated as is a homopolymer in GPC interpretation. In particular, intrinsic viscosity measurements could then lead to estimates of molecular weight via the universal calibration curve. 

Intrinsic viscosity measurements were done with a large number of solvents varying in pH, ionic strength, etc., using Cannon-Ubbelohde semimicro dilution viscometers. This was done to provide information on the effect of mobile phase composition on the size of a polymer molecule in solution and thus to facilitate the interpretation of GPC behavior. 

Dilute Solution Viscometry - The hydrogenated and hydroformyl ated (10%) PBD were completely soluble in toluene. Intrinsic viscosity measurements were carried out in toluene at 30°C using a Cannon-Ubbelohde viscometer. 

All copolymers were prepared by solution polymerization, under adiabatic conditions, giving at least 99.9% conversions. The polymer gels were granulated and then dried at 90 °C to a residual water content of 10 to 12%. The active polymer content of each sample was calculated from the initial weight of the comonomers and the weight of the dried gel. Hydrolysis of the polymers was determined by conductometric titration to be less than 0.2% of the acrylamide charge. The molecular weight of the polymers was 8-10 million as determined by intrinsic viscosity measurements. 

Intrinsic-viscosity measurement leads to the viscosity-average Molecular weight, which may be defined as under ... 

Figure 13.20 The rate of thermal degradation of PET as a function of the intrinsic viscosity measured at different temperatures 1, 280 °C 2, 290°C 3, 300°C 4, 310°C [29b, 29c, 39], From Thermal degradation of PET. A kinetic analysis of gravimetric data, Covney, J. D., Day, M. and Wiles, D. M., J. Appl. Polym. Sci., 28, 2887 (1983), copyright (1983 John Wiley Sons, Inc.). Reprinted by permission of John Wiley Sons, Inc.

Much easier, and with higher precision, on-line intrinsic viscosity measurements are possible. Unfortunately, new problems arise from the insufficiently well known interdependence between g and g. The relationship between the intrinsic viscosity and the radius of gyration is fairly well settled for linear chains [3,71] and is satisfactorily described by the Fox-Flory equation (Eq. 21), but for the branched chains the 0-factor for branched chains may be different. In general one has [49]... 

This study addresses two questions 1) Is polymer aggregation in solutions directly related to solvent quality 2) If not, does solvent quality exert an effect on the viscosity of semidilute solutions separate from the effect of aggregation The copolymer poly(vinylbutyral) (PVB) was chosen for this investigation. PVB is known to aggregate in several solvents (IS). Light scattering and intrinsic viscosity measurements were used to assess solvent quality. Viscosities were measured at one concentration in three solvents and temperatures from 25 to 55 C. 

Intrinsic Viscosity. Due to the complicating effects of aggregation and selective adsorption on the A2 values determined by light scattering, another means was sought to characterize the quality of solvents for PVB. The alternate means chosen was intrinsic viscosity measurements. Theory relates the intrinsic viscosity to the polymer chain dimensions through the expression (24)... 

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