Alginate viscosity

Algin Viscosity stabilizer for starch-dextrin and latex-type adhesives ... 

FDA testing and previous studies have verified that 150-250 cP is an ideal range for decreased sodium alginate injection resistance in many standard over-the-wire microcatheter systems and increased calcium alginate stability in gel form (Becker et al, 2005 2007). As for newer flow-directed microcatheter systems, an injectable biomaterial requires a lower alginate viscosity range (1-150 cP) to accommodate the microcather s minimal inner diameter. 

The viscosity of algiaate solutioas is iadepeadeat of pH ia the range 5—10, but below pH 4.5, the viscosity iacreases uatil the pH reaches 3 whea iasoluble alginic acid precipitates. Propyleae glycol algiaate is soluble and stable at pH 2—3 but not above 6.5. 

The flow properties of sodium alginate solutions depend on concentration. A 2.5% medium viscosity sodium alginate solution is pseudoplastic, especially at the higher shear rates in the range of 10—10,000/s. 

Thickeners. Thickeners increase the viscosity of the polychloroprene latex adhesives. Amounts up to 1% of polyacrylates, methyl cellulose, alginates and polyurethane thickeners can be used. Particular attention should be paid to fluctuations in pH when thickener is added in the formulations. For low-pH (7-10) formulations, fumed silica or some silicates can be used. 

Dextrans are particularly useful and are employed as a plasma substitute. A concentration of about 6% dextran (50,000-100,000 relative molecular weight) has equivalent viscosity and colloid-osmotic properties to blood plasma. Dextran can also be used as non-irritant absorbent wound dressings, an application also suited to alginate gels. 

Flavor emulsions are similarly stabilized by the viscosity produced upon addition of a vegetable gum, such as tragacanth, Irish moss extract, arabic, a cellulose gum, or one of the alginates, to the aqueous phase. Here the oil phase, in the form of the flavor, is in small proportion to the water. In the absence of the acetic acid, contained in the vinegar of the French dressing. 

Sodium alginate (algin) is one of the most widely used hydrocolloids for ice cream. It is supplied in several viscosity types. The lower viscosity material is recommended in order to prevent thick mixes. It is used at a level of 0.15 to 0.25%. It is added to mix at higher temperatures in order to minimize precipitation by calcium salts present in milk products. Sodium alginate is sensitive to high acidities often developed in some mixes and causes thickening. 

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 substance used in latex compounding to increase the viscosity of the mix. Examples are alginates, casein, certain clays and methyl cellulose. 

Agarose/ Alginate Dextran/Calcium Chloride Agarose is the thermally gelled precast polmer Dextran adjusts the viscosity. 10... 

Figure 1.30. Evolution of the water phase viscosity rjc as a function of the shear rate and alginate concentration (filled symbols). For the sake of comparison, the viscosity rja of the inverted emulsion at 0, = 75 wt% is reported in the same graph (open symbols). (Adapted from [162].)...

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