Hydroxyethyl cellulose stability

Melhylenebls (6-l-bulyl-4-melhylphenol) Slearyl citrate stabilizer, org. pigments Zephrym PD3315 stabilizer, org. solvent systems Ethyl hydroxyethyl cellulose stabilizer, org. substrates Hexamethylenebis (3.5-di-t-butyl-4-hy oxycinnamate/, Irganox 259 ... 

Barium dinonyinaphthalene sulfonate Ethyl hydroxyethyl cellulose stabilizer, PS... 

Hydroxyethyl cellulose (HEC), a nonionic thickening agent, is prepared from alkali cellulose and ethylene oxide in the presence of isopropyl alcohol (46). HEC is used in drilling muds, but more commonly in completion fluids where its acid-degradable nature is advantageous. Magnesium oxide stabilizes the viscosity-building action of HEC in salt brines up to 135°C (47). HEC concentrations are ca 0.6—6 kg/m (0.2—21b/bbl). 

Poly(vinyl acetate) emulsions can be made with a surfactant alone or with a protective coUoid alone, but the usual practice is to use a combination of the two. Normally, up to 3 wt % stabilizers may be included in the recipe, but when water sensitivity or tack of the wet film is desired, as in some adhesives, more may be included. The most commonly used surfactants are the anionic sulfates and sulfonates, but cationic emulsifiers and nonionics are also suitable. Indeed, some emulsion compounding formulas require the use of cationic or nonionic surfactants for stable formulations. The most commonly used protective coUoids are poly(vinyl alcohol) and hydroxyethyl cellulose, but there are many others, natural and synthetic, which are usable if not preferable for a given appHcation. 

Fluidized aqueous suspensions of 15% by weight or more of hydroxyethyl-cellulose, hydrophobically modified cellulose ether, hydrophobically modified hydroxyethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and polyethylene oxide are prepared by adding the polymer to a concentrated sodium formate solution containing xanthan gum as a stabilizer [278]. The xanthan gum is dissolved in water before sodium formate is added. Then the polymer is added to the solution to form a fluid suspension of the polymers. The polymer suspension can serve as an aqueous concentrate for further use. 

A new class of amphiphilic, surface-active graft copolymers, hydrophobically modified hydroxyethyl celluloses (HM-HEC s), are comprised of a cellulose backbone with short polyethylene oxide (PEO) and grafted alkyl side chains. They are excellent steric stabilizers of 0/W emulsions. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

The stabilizing of aqueous latexes succeeded by using emulsifiers (anionic, nonionic) and/or their mixture, steric stabilizators (polyvinyl alcohol (PVOH), hydroxyethyl cellulose, polyethylene glycol, new protective colloids etc.), and polymerizable surfaces active agents, in general. Vinyl acetate (VAc) emulsion homopolymers and copolymers (latexes) are widely used as binders in water-based interior and exterior architectural paints, coatings, and adhesives, since they have higher mechanical and water resistance properties than the homopolymers of both monomers [2, 4, 7]. 

Typical suspension stabilizers for the production of EPS are water-soluble, surface-active macromolecules, such as poly (vinyl alcohol) (PVA), hydroxyethyl-cellulose (HEC) and polyvinylpyrrolidone (PVP), or natural products, such as gelatin [36-40], and insoluble inorganic powders, such as tricalcium phosphate (TCP), also called picketing stabilizer , mostly in combination with surfactants called extenders [33-35,44], or a combination of these [129]. The differences and specialties of these stabilizing mechanism are described briefly below ... 

In this section, we discuss about the screen printed electrode (SPE) based AChE sensors for the selective determination of OP and CA pesticides. In the past decades, several attempts were made by the researchers to develop SPE based pesticide sensors, where the enzyme AChE was immobilized either directly onto the electrode or above other matrices incorporated SPE surfaces. Both approaches resulted in the good, rapid detection of OP and CA pesticides. Earlier, Hart et al. employed AChE/SPE to detect OP and CA pesticides [21], They measured the enzyme activity from the rate of hydrolysis of acetylthiocholine iodide. Three polymers such as hydroxyethyl cellulose, dimethylaminoethyl methacrylate, and polyethyleneimine were used as enzyme immobilization matrices. Initially, electrodes were exposed to drops of water or pesticide solution, dried and their activity was screened after 24 h. They found that, when the enzyme matrix was hydroxyethyl cellulose, electrode activity inhibited both by water as well as by pesticides. While with co-polymer matrix, a significant response towards pesticides alone was observed. Further, the long-term storage stability of electrodes was highest when the enzyme matrix consisted of the co-polymer. The electrodes retained their activity for nearly one year. In contrast, the electrodes made of hydroxyethyl cellulose or polyethyleneimine possess less stability. 

FIG. 11 Pseudophase diagram for 30 wt% cyclohexane in water stabilized by PAA (Carbopol 980). The c values are shown as the curve drawn in the bottom left-hand corner of the diagram. (Reprinted from Colloids and Surfaces A Physicochem Eng Aspects, 88, Lockhead RY, Rulinson CJ, An investigation of the mechanism by which hydrophobically modified hydrophilic polymers act as primary emulsifiers for oil in water emulsions. 1. Poly(acrylic acids) and hydroxyethyl celluloses. 27-32, Copyright (1994), with permission from Elsevier Science.)... 

Aicoramnosan. [Vevy] Hydroxyethyl-cellulose thicl er, suspending tgent stabilizer for vinyl polymerization binder in ceramic glazes used in paper and textile sizing. 

The types of surface moieties stabilizing the latex also are important. The binders used in waterborne coatings are not the hard-sphere, model polymer colloids used in adsorption studies. They are soft (low glass transition temperature), deformable moieties that are stabilized by grafted polymer fragments [e.g., (hydroxyethyl)cellulose (16) or poly(vinyl alcohol)] or by terpolymerized acid monomers extended from the surface of the colloid (IT). Such stabilizers produce a far less hydrophobic surface than is generally depicted in colloid texts. This situation is particularly true if the composition of the latex is predominately methacrylate or vinyl acetate, as they are in most U.S. commercial products. 

Depletion layer effects occur in associative thickener formulations when the latex is larger in size ( 500 nm) and not highly stabilized with surface (hydroxyethyl)cellulose fragments. Syneresis is also observed in simple aqueous solutions and in latex dispersions when the hydrophobicity of the associative thickener is high. 

Sperry et al. found that the addition of either the anionic surfactant sodium dodecyl sulphate or the nonionic surfactant Triton X-405 completely desorbed any hydroxyethyl cellulose from the surface of the latex particles. This meant that, even in the presence of free hydroxyethyl cellulose in the continuous phase, none of the flocculating polymer was attached to the surface. The latex particles in the presence of the sodium dodecyl sulphate (0-5%) were thus electrostatically stabilized whereas the nonionic Triton surfactant conferred steric stabilization. 

Equation (16.16) suggests that Vj should depend approximately upon the molecular weight of the free polymer with an inverse power of ca 0-4-0-5. This is significantly less than the exponent of -0-7 measured experimentally (Sperry et al, 1981) for the flocculation of aqueous latices, sterically stabilized by poly(oxyethylene), using hydroxyethyl cellulose. The latter, however, are extremely stiff chains. 

Although the actual diameter of a polymeric particle can be measured by microscopic or other methods, the effective diameter for hydrodynamic puiposes, and hence the effective volume fraction, may be considerably larger. Surface layers can significantly increase the effective volume of latex particles. Such layers may be due to adsrxbed surfactants, adsrabed or reacted polymeric stabilizers such as poly(vinyl alcohol), hydroxyethyl cellulose or poly(ethylene oxide), and surface charges on the polymer particle. The smaller the particle size, the greater will be the contribution a surface layer (rf given thickness to the effective volume of flie particle. 

Dehnition Polymeric quaternary ammonium salt of hydroxyethyl cellulose reacted with a lauryl dimethyl ammonium substituted epoxide Uses Stabilizer for emulsions thickener for surfactant systems antistat, film-former in cosmetics substantive conditioner for hair and skin care prods. 

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