Hydroxypropyl cellulose stability

Paine et al. [85] extensively studied the effect of solvent in the dispersion polymerization of styrene in the polar media. In their study, the dispersion polymerization of styrene was carried out by changing the dispersion medium. They used hydroxypropyl cellulose (HPC) as the stabilizer and its concentration was fixed to 1.5% within a series of -alcohols tried as the dispersion media. The particle size increased from only 2.0 /itm in methanol to about 8.3 /itm in pentanol, and then decreased back to 1 ixm in octadecanol. The particle size values plotted against the Hansen solubility parameters... 

Dispersion polymerization involves an initially homogeneous system of monomer, organic solvent, initiator, and particle stabilizer (usually uncharged polymers such as poly(A-vinyl-pyrrolidinone) and hydroxypropyl cellulose). The system becomes heterogeneous on polymerization because the polymer is insoluble in the solvent. Polymer particles are stabilized by adsorption of the particle stabilizer [Yasuda et al., 2001], Polymerization proceeds in the polymer particles as they absorb monomer from the continuous phase. Dispersion polymerization usually yields polymer particles with sizes in between those obtained by emulsion and suspension polymerizations—about 1-10 pm in diameter. For the larger particle sizes, the reaction characteristics are the same as in suspension polymerization. For the smallest particle sizes, suspension polymerization may exhibit the compartmentalized kinetics of emulsion polymerization. 

For (a), hydroxypropyl cellulose (HPC) (6-8), poly(vinyl pyrrolidone) (PVP) (9,10), poly(acrylic acid) (PAA) (9), and poly(dimethyl siloxane) (PDMS) (11) are usually employed. Ober et al. reported that the copolymers of isobutylene/isoprene and various methacrylates, which have weak polarity, are appropriate stabilizers for... 

Polymeric steric stabilizer such as poly(vinylpyrrolidone) (PVPo),poly(acrylic acid), poly(hydroxypropyl)cellulose, etc., are used to prepare monodisperse polymer in dispersion polymerization of monomers such as alkyl acrylates and methacrylates, and styrene in polar media. AB and ABA block copolymers are a second type of steric stabilizer which can be used in dispersion polymerization. For example, the poly(styrene-h-ethylene oxide) was recently used by Winnik et al. [6] in the dispersion polymerization of styrene in methanol. 

During dispersion polymerization polymer particles are formed from an initially homogeneous reaction mixture by polymerization in the presence of a polymeric steric stabilizer. The process is applicable to monomers which yield polymers that are insoluble in a solvent for the monomer. Styrene has been polymerized in alcohols, with steric stabilizers such as poly(A -vinylpyrrolidone) (see Fig. 1-4 for monomer structure) or hydroxypropyl cellulose. Hydrocarbon... 

Hydroxypropyl cellulose is also used in cosmetics and in food products as an emulsifier and stabilizer. 

Viscosity (dynamic) a wide range of viscosity types are commercially available see Table V. Solutions should be prepared by gradually adding the hydroxypropyl cellulose to a vigorously stirred solvent. Increasing concentration produces solutions of increased viscosity. See also Section 11 for information on solution stability. 

Aqueous hydroxypropyl cellulose solutions have optimum stability when the pH is maintained at 6.0-8.0, and also when the solution is protected from light, heat, and the action of microorganisms. 

It is also used in hot-melt extruded films for topical use. When it is produced with chlorpheniramine maleate, the matrix is stabilized, allowing film processing at lower temperatures. Mucoadhesive hydroxypropyl cellulose microspheres have been prepared for powder inhalation preparations. A specification for hydroxypropyl cellulose is included in the Food Ghemicals Godex (EGG). 

Prodduturi, S., Manek, R.V., Rolling, W.M., Stodghill, S.P., Repka, M.A. Water vapor sorption of hot-melt extruded hydroxypropyl cellulose films Effect on physico-mechanical properties, release characteristics, and stability. J. Pharm. Sci. 2004, 93(12), 3047-3056. 

Conversions of alkali cellulose with ethylene oxide or propylene oxide, on the other hand, proceed without alkali consumption. The newly formed hydroxyl groups can also add on ethylene oxide or propylene oxide molecules. Commercially produced hydroxypropyl cellulose, with DR = 4, dissolves in water below 38 C. It can be thermoplastically processed and so is used to manufacture water-soluble packaging film, as an adjuvenant in pharmaceutics and confectionery, as a whipped cream stabilizer, as a binder for ceramics, as a suspending agent in emulsion polymerization, etc. 

Hydroxypropyl cellulose (HPC) is used for the preparation of artificial tears, treat medical conditions characterized by insufficient tear production such as kerotoconjunctivitis sicca, recurrent corneal erosions, decreased corneal sensitivity, exposure, and neuroparalytic keratitis. It is also used as a disintegrant and a binder in tablets, sieving matrix for DNA separations by capillary and microchip electrophoresis and lubricant for artificial eyes, food additive, thickener, and as an emulsion stabilizer [111, 112]. 

In a typical experiment 1.0 mL pyrrole (vacuum-distilled from KOH and stored in the dark at —30°C under argon prior to use) is added to a stirred solution of 5.47 g FeCls and 0.3-1.Og stabilizer (hydroxypropyl cellulose, poly(vinylalcohol), poly(vinylpyridine), poly(ethyleneoxide) or their copolymers) in 100 mL of deionized water at 25 °C. The reaction mixture is stirred for at least 24 h and then centrifuged until a clear yellow-green supernatant is obtained (the centrifugation time and speed vary according to the particle size of individual samples). The resulting sediments are washed several times with 2-3 mL water and allowed to dry under ambient conditions for several days. 

Two types of stabilizers are used, one of which is basically the type of water-soluble polymers (often in the presence of an electrolyte or a buffer) and the other is a type of water-insoluble inorganic compounds. The former type includes polyvinyl alcohol (PVA), hydroxypropyl cellulose, sodium poly(styrene sulfonate), and sodium salt of acrylic acid-acrylate ester copolymer. The latter type includes magnesium silicate hydroxide (TALC), hydroxyapatite, barium sulfate, kaolin, magnesium carbonate and hydroxide. 

Maji S, Kundu S, Pinto LFV, Godinho MH, Khan AH, Acharya S (2013) Improved mechanical stability of acetoxypropyl cellulose upon blending with ultranarrow PbS nanowires in Langmuir monolayer matrix. Langmuir 29(49) 15231-15239 Mays JW (1988) Solution properties and chain stiffness of cyanoethyl hydroxypropyl cellulose. Macromolecules 21(11) 3179-3183... 

Spherical silica particles containing retinol have been fabricated using O/ W/O multiple emulsion and the sol-gel method (Lee et al., 2001). O/W/O multiple emulsions were stabilized with hydroxypropyl cellulose (HPC) and surfactants such as Tween 20 and Span 80. In addition a polymeric stabilizer present in the intermediate aqueous phase was shown to improve the encapsulation efficiency. In the presence of polyvinyl alcohol the yield of encapsulation efficiency of retinol was 7%. With Pluronic P123 (a block copolymer of ethylene oxide propylene oxide) a yield of encapsulation of 31% could be reached. Figure 7.24 shows the retinol released profile from silica particles prepared in the O/W/O multiple emulsions and stabilized with different surfactant and different polymeric stabilizers in the intermediate aqueous phase. 

Good leveling, no sagging and storage stability are influenced by addition of thickeners, such as - xanthane gum, -+methylcellulose, carboxy-methyl cellulose or - ethyl hydroxypropyl cellulose in emulsion paints. Other additives in this respect are hydrogenated - castor oil, stand oils (- drying oils), fatty acid amides and - metallic soaps, which are used in solvent-based or solvent fi ee formulations. 

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