Suspension molecular weight measurements

A highly reactive form of titanocene could be obtained when a suspension of the gray-green hydride 14 was stirred in ethyl ether for 2 hours at room temperature. The solid gradually disappeared concurrent with the evolution of 0.5 equivalent of H2 per equivalent of Ti. Molecular weight measurements showed this metastable form of titanocene (15) to be dimeric. Treatment of a cold ethereal solution of (Cp2Ti)2 (15) with CO resulted in a quantitative yield of Cp2Ti(CO)2 (1) (24,36). 

Enzymatic degradation is mainly evaluated by means of (1) weight loss of polymeric materials, (2) optical density of polymer suspensions, (3) titration of water-soluble materials, (4) molecular weight measurement, (5) physical property... 

This unit describes a method for measuring the viscosity (r ) of Newtonian fluids. For a Newtonian fluid, viscosity is a constant at a given temperature and pressure, as defined in unit hi. i common liquids under ordinary circumstances behave in this way. Examples include pure fluids and solutions. Liquids which have suspended matter of sufficient size and concentration may deviate from Newtonian behavior. Examples of liquids exhibiting non-Newtonian behavior (unit hi. i) include polymer suspensions, emulsions, and fruit juices. Glass capillary viscometers are useful for the measurement of fluids, with the appropriate choice of capillary dimensions, for Newtonian fluids of viscosity up to 10 Pascals (Newtons m/sec 2) or 100 Poise (dynes cm/sec 2). Traditionally, these viscometers have been used in the oil industry. However, they have been adapted for use in the food industry and are commonly used for molecular weight prediction of food polymers in very dilute solutions (Daubert and Foegeding, 1998). There are three common types of capillary viscometers including Ubelohde, Ostwald, and Cannon-Fenske. These viscometers are often referred to as U-tube viscometers because they resemble the letter U (see Fig. HI.3.1). 

Figure 1. Effects of the concentration of dextrans with various molecular weights on three indices of BBC aggregation (16). MAI indicates the average number of RBCs in each aggregation unit counted under the microscope. ESR is the maximum rate of sedimentation of erythrocytes in a calibrated tube, with corrections made for changes in viscosity and density of the suspending medium following the addition of dextrans. The relative viscosity (t)r) is the ratio of the viscosity of RBC suspension to that of the suspending medium at a shear rate fo 0.1 sec 1. The RBC concentration of the suspension was 1% for MAI and 45% for ESR and r)r measurements. The vertical bars represent SEM. (A), Dx 40 (O), Dx 80 (M), Dx 150 (A), Dx 500 ( ), Dx 2000.

Fig. 9. Shear viscosity ratio of PDMS suspensions of silane-treated glass spheres (ca. 10 mm in diameter) to that of identical bare glass spheres at the same volume fraction ( )=0.28> measured at T=25 °C in steady state for three PDMS molecular weights, reproduced from [48]...

The rate of polymerization was determined from the amount of polymer obtained per unit of time. The productivity of the metallocene catalyst was calculated from the quantity of polymer and the catalyst metal fed into the reactor. The resulting polymers were investigated by gel permeation chromatography (GPC) to determine the molecular weight distribution together with the average molecular weights. The density was measured on pressed films by means of the suspension method in a mixture of water and isopropanol. 13C-NMR-spectroscopy was applied to analyze the composition of copolymers and to evaluate their structure. 

Once the optical constant was known, the turbidity of the flocculated suspension calculated from Equation 11, using the known particle size distribution, could be compared with the experimentally measured turbidity. Correlations were made between particle size distributions and turbidity readings as the PEI molecular weight and dose were varied. The velocity gradient in the stirrer-reactor was held constant at G = 20 sec Other experiments indicate that the influence of varying the velocity gradient in the range G = 20 to 60 sec" on either turbidity or particle size distribution was minor. 

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