Hydroxyethylcellulose weight

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. 

Figure 4.40 shows the shear-thinning behavior of an aqueous solution of ethyl hydroxyethylcellulose as a function of the concentration. The pseudoplastic behavior is observed at lower polymer concentrations as the molecular weight of the polymer increases. An aqueous solution of ethyl hydroxyethylcellulose becomes pseudoplastic at concentrations of less than 1%. Above the critical value of the shear stress the flow behavior is non-Newtonian, and viscosity decreases with the increasing shear stress. The critical stress is in the range of 0.1 N/m2 for the solution. 

The case of uncharged hydroxyethylcellulose (HEC), the parent molecule of JR polymers, deserves special mention. (The specimen chosen had a molecular weight of —400,000, about the same as Polymer JR 400.) First, although the uptake is small, it is finite. Second, the isotherm is flat, typical of true adsorption but atypical of a process involving bulk diffusion. Using the BET surface area of hair, viz., 0.1 m /g (7), and con-... 

The in situ process is simpler because it requires less material handling (37) however, this process has been used only for resole resins. When phenol is used, the reaction system is initially one-phase alkylated phenols and bisphenol A present special problems. As the reaction with formaldehyde progresses at 80-100°C, the resin becomes water-insoluble and phase separation takes place. Catalysts such as hexa produce an early phase separation, whereas NaOH-based resins retain water solubility to a higher molecular weight. If the reaction medium contains a protective colloid at phase separation, a resin-in-water dispersion forms. Alternatively, the protective colloid can be added later in the reaction sequence, in which case the reaction mass may temporarily be a water-in-resin dispersion. The protective colloid serves to assist particle formation and stabilizes the final particles against coalescence. Some examples of protective colloids are poly(vinyl alcohol), gum arabic, and hydroxyethylcellulose. 

Figure 3.7 Effect of matrix molecular weight on the electrophoretic mobility, using as probes restriction fragments of size (a) 72, (b) 603, and (c) 23 130 base pairs. Matrix polymers and their were hydroxypropylcellulose ( 100 kDa, 0 300 kDa), polyacrylamide (A 0.7-1.0 MDa, + 1.14 MDa), and hydroxyethylcellulose (O 1 32 MDa). Original measurements were by Barron, et al.(5,6).

Cellulosic adhesives - Cellulose is a naturally occurring water insoluble polymer which is a major component of plants - wood is 60% cellulose. It is a polysaccharide very similar to starch except that the saccharide imits of the macromolecules are eonnected by beta-linkages in contrast to the alpha linkage for starch. Cellulose ean be reacted with various acids to produce water soluble adhesives such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, or organic solvent soluble polymers such as hydroxypropylcellulose and cellulose acetate. The polymers have molecular weights of about 25,000 and are used for adhesives in paper, textile, plastic, and leather shoes. 

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