Viscosity of high molecular weight

A 1 Alexander, P., and K. A. Stacy The light-scattering and non-Newtonian viscosity of high molecular weight polymethacrylic acid. Trans. Faraday Soc. 51, 299 (1955). 

The non-newtonian viscosity of high molecular weight PEO samples is very different in water and water-isopropanol mixture. 

In mechanical degradation, chain scission does not occur from individual attack on a specific atom of the macromolecular chain, but from the application of a critical stress. The extensional viscosities of high-molecular-weight, synthetic polymers have been studied for the past two decades, in attempts to relate the values with drag reduction behavior. To date the dynamic uniaxial extensional viscosities of aqueous carbohydrate solutions have not been reported. 

Cowan, M.E., Garner, C., Hester R.D. and McCormick, C.L. (2001) Experimentally determined drag reduction efficiency and extensional viscosity of high molecular weight polymers in dilute aqueous solution. J. App. Poly. Sei., 82, 1222-1231. 

The viscosity of a liquid increases with pressure. This behavior is relatively small for liquids of high molecular weight and low compressibility the effect can be estimated by Kouzel s method (1965) ... 

Viscosity additives are aliphatic polymers of high molecular weight whose main chain is flexible. It is known that in a poor solvent, interactions between the elements making up the polymer chain are stronger than interactions between the solvent and the chain (Quivoron, 1978), to the point that the polymer chain adopts a ball of yarn configuration. The macromolecules in this configuration occupy a small volume. The viscosity of a solution being related to the volume occupied by the solute, the effect of polymers on the viscosity in a poor solvent will be small. 

The preparation of high molecular weight PPT in HMPA/NMP shows a strong dependence of inherent viscosity on reactant concentrations. In 2 1 (by volume) HMPA/NMP, the highest inherent viscosity polymer is obtained when each reactant is present in concentrations of ca 0.25 M higher and lower concentrations result in the formation of polymer of lower inherent viscosities. A typical procedure is as foUows 1,4-phenylenediamine, HMPA, and NMP are added to an oven-dried resin ketde equipped with a stirrer and stirred for ca 15 min with cooling to — 15°C, foUowed by the addition of powdered terephthaloyl chloride to the rapidly stirred solution. The reaction mixture changes to a thick, opalescent, paste-like gel in ca 5 min. 

Fluid or Pour-Tjpe Resins. Fluid or pour-type resins are modified acryHc systems that can be cured chemically. A fine-particle-size polymer powder consisting mostly of high molecular weight material is preferred to prevent a rapid increase in viscosity during mixing and pouring. Polymerization occurs in flexible... 

Addition cure silicones can be delivered from solvent, waterborne emulsions, or 100% solids systems. The solvent free versions employ base polymers of intermediate molecular weight to achieve processable viscosity. These base polymers can have reactive moieties in terminal and/or pendant positions. These lower molecular weight, more functional systems result in a tighter crosslink network which feels rubbery to the hand. Low amounts of high molecular weight additives are included in some formulations to provide a more slippery feel [51,52]. 

The dissolution of high molecular weight analytes increases the viscosity of the samples. Samples with a high viscosity can exhibit viscous fingering on the column top. Because this phenomenon can impair resolution, it is recommended to keep the sample concentration below certain limits. These limits are shown in Table 11.5. 

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