Viscosity hydroxypropylcellulose

HPC isotropic film, where E is the Young s modulus, and are yield and tensile stress, respectively. Similar results were obtained by Zimmermann et al. from isotropic aqueous solutions of low viscosity hydroxypropylcellulose (HPC, 5 wt%) with microfri-brilated cellulose (1,5,10 and 20 wt%) [55]. 

The viscosity of an emulsion can be of crucial importance for its stability, especially the viscosity of the external phase. A high viscosity reduces creaming and also lessens the tendency of particles to coalescence and produce phase separation. Examples of the widely used viscosity-imparting agents are alginates, bentonite, carboxymethylcellulose, polyvinyl pyrrolidone, hydroxypropylcellulose, and carbomer. 

A popular approach to improve ocular drag bioavailability is to incorporate soluble polymers into an aqueous solution to extend the drug residence time in the cul-de-sac. It is reasoned that the solution viscosity would be increased and hence solution drainage would be reduced. The more commonly used viscolyzing agents include PVA and derivatives of cellulose. Cellulosic polymers, such as methylcellulose, hydroxyethylcellulose (HEC), hydroxypropyl-methylcellulose (HPMC) and hydroxypropylcellulose (HPC), are widely used as viscolyzers showing Newtonian properties. They have common properties ... 

Chemical modification of hydroxyethylcellulose or hydroxypropylcellulose with long-chain hydrocarbon alkylating reagents, such as C8-C24 epoxides or halides, has been reported to yield novel water-soluble compositions exhibiting enhanced low-shear-rate solution viscosities and polymeric surfactant properties [ 104,105]. Patents have also been issued for water-soluble phosphonomethylcellulose and phosphonomethylhydroxyethylcellulose [106,107]. 

Figure 11.7 Viscosity versus shear-rate curve for 60% hydroxypropylcellulose (HPC) in water, made from two different batches of of Klucel E. The power-law slopes at low shear rate are —0.51 for Lot 8195 and —0.56 for Lot 7590. (From Walker and Wagner 1994, with permission from the Journal...

Other non-ionic cellulose ethers which have been stndied in the formulation of hydrophilic matrices include high viscosity grades of hydroxypropylcellulose (HPC) and hydroxyethylcellulose (HEC) [24]. The ionic cellulose ether, sodium carboxymethylcellulose (Na CMC), with low or medium viscosity grades has... 

FIGURE 1.12 Viscosity of hydroxypropylcellulose (nominal molecular weight M=10 g/mol) in water and fits to stretched exponential and power-law concentration dependence. (From Phillies and Quinlan [1995], with permission. Copyright 1995 American Chemical Society.)... 

Aluminum starch octenyl succinate viscosity control agent, foam rubber Lauramine oxide viscosity control agent, food Hydrogenated palm kernel oil Hydroxypropylcellulose Karaya (Sterculia urens) gum PEG-4 dilaurate PEG-150 distearate... 

Celluloses are described by the type of substituent carried by the cellulose backbone and the viscosity. They can separate DNAs at low concentrations (<2%). Hydroxyethylcellulose (HEC) is a linear derivative with bulky ethylene oxide side chains terminating in hydroxyl groups. In aqueous solutions, it has a stiff, extended conformation. It has relatively high viscosities at the entanglement concentration. A mixture of HEC of different sizes offers a wide range of DNA separation from 100 bp to 23 kbp. Hydroxypropylcellulose (HPC) solution provides similar separation ability, and it has 2-3 times lower viscosity than HEC solution. 

CMC is compatible with most water-soluble nonionic gums over a wide range of concentrations. When a solution of CMC is blended with a solution of a nonionic polymer such as hydroxyethylcellulose or hydroxypropylcellulose, a synergistic effect on viscosity is usually observed. Such blends produce solution viscosities considerably higher than would ordinarily be expected. This effect is reduced if other electrolytes are present in the system. 

Hydroxypropylcellulose [molar ratio of propylene oxide to cellulose = 105 305 viscosity (2% aqueous solution) less than 50Cpl (0.1) Methy hydroxypropylcellulose (0.34)... 

This paper treats an extensive study (1,2,17,18) of i obe diffusion in aqueous solutions of the high-molecular-weight polymer hydroxypropylcellulose (HPC), which is rodlike, semiflexible, and uncharged. Several factors motivated our choice of this system 1) Earlier studies (19.20,21) of i obe diffusion in HPC revealed the bimodality of probe spectra. However, the physical properties and detailed parameterization of the lineshapes for the two modes were non-trivial and incompletely characterized. An objective of our wturk was to provide a more thorough study of ohservahle lineshape parameters. 2) The viscosity q of aqueous HPC solutions shows, at elevated concentration, an apparent change in the functional form of its concentration dependence. An objective of this paper is to resolve between possible interpretations of this change. 

Bu and Russo used FRAP to measure the diffusion of fluorescein and nine larger probes through hydroxypropylcellulose solutions(22). Nominal matrix molecular weights were 60,300, and 1000 kDa. Detailed results were presented for the 300 kDa matrix polymer, as seen in Figure 9.13. Fluorescein diffusion was nearly unimpeded by the matrix polymer. Probe particles diffuse more rapidly than expected from the macroscopic solution viscosity. Note that increased toward rj with increasing R, and Dp(c) for each probe fits well to a simple exponential, except perhaps for the largest probe. Comparison was made by Bu and Russo with the Langevin-Rondelez equation, which describes these data well(23). 

Studies of hydroxypropylcellulose water solutions were motivated by viscosity measurements indicating the presence of a transition in the functional form of t c) at a well-defined molecular-weight-dependent concentration c+. Probe diffusion studies confirmed the physical reality of the transition, i.e., the transition is not a mathematical fitting artifact without exception, the parameters characterizing g q, t) have qualitative changes in their concentration dependences at the same concentration c+. 

As part of a study of probe diffusion, Yang and Jamieson report the shear viscosity T] (Figure 12.6c) of hydroxypropylcellulose solutions(29). The z-average molecular weights were 110,140,450, and 850 kDa solution viscosities r]/rjQ were as large as 45. The 7 (c) for each molecular weight is described well by a stretched exponential. 

Hydroxypropylcellulose is noteworthy in having a pseudotheta transition near 40 C. Solutions are water-white at lower temperatures but become cloudy near and above this temperature. The viscosities of aqueous solutions of 139,146,415,... 

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