Dispersities substitution

Deposition on fibers or fabrics Vapor phase deposition Deposition in nanoscale matrices Photochemically initiated polymerization Enzyme-catalyzed polymerization Polymerization using electron acceptors Miscellaneous polymerization methods Routes to more processible polyanilines Emulsion polymerization Colloidal polyaniline dispersions Substituted polyanilines... 

The average reduction of the reinforcement ratio in the boundary zone is obtained upon averaging over all possible values of t. A value of 0.58 is found for a 3-D UR fibre dispersion. Substitution in eq (13) for values of m between roughly 0.2 and 0.4 demonstrates the reinforcement ratio of a partially planar fibre composite to decrease in the boundary layer to 70 to 80% of its bulk value ... 

Because of the high melt viscosity of polyolefins, normal spinning melt temperatures are 240—310°C, which is 80—150°C above the crystalline melting point. Because of the high melt temperatures used for polyolefin fiber spinning, thermal stabilizers such as substituted hindered phenols are added. In the presence of pigments, the melt temperature must be carefully controlled to prevent color degradation and to obtain uniform color dispersion. 

Larch arabinogalactan is approved in 21 CFR 172.610 as a food additive for use as an emulsifier, stabilizer, binder or bodying agent for essential oils and noimutritive sweeteners, flavor bases, nonstandardized dressings, and pudding mixes. It has also been used in the preparation of cosmetic and pharmaceutical dispersions and as an emulsifier in oil—water emulsions (69). Industrially, the main use has been in Hthography as a gum arabic substitute. 

Aqueous dispersions are alternatives to solutions of Hquid and soHd resins. They are usuaUy offered in 50% soHds and may contain thickeners and cosolvents as stabilizers and to promote coalescence. Both heat-reactive (resole) and nonheat-reactive (novolak) systems exist that contain unsubstituted or substituted phenols or mixtures. A related technology produces large, stable particles that can be isolated as discrete particles (44). In aqueous dispersion, the resin stmcture is designed to produce a hydrophobic polymer, which is stabilized in water by an interfacial agent. 

Color intensity and permanence are improved by metal carboxylate salts, especially 2inc salts (83), which cataly2e the dye development and stabili2e the dye in its colored form. The substituted novolak resin, along with extender and binder, can be apphed to the receiving sheet as a solution or aqueous dispersion. Aqueous dispersions are probably the most widely used they are manufactured by the resin suppher or the user from the base resin. 

Substituted amides (not of the alkanolamide variety) are sold to diverse low volume markets. They have some utility ki polymers such as polyethylene, ethylene-vinyl acetate copolymers, acryUc polymers, PVC, polyamides, and polyesters. They have been found effective as pharmaceutical processkig aids, defoamers (qv), antimicrobials, pesticides, kisect repellents, dispersion stabilizers, and corrosion inhibitors. 

This is because the effect of the dispersed soHd, rather than the dispersing medium, is usually more significant. However, the latter should not be ignored. Many industrial problems involving unacceptably high viscosities in dispersed systems are solved by substituting solvents of lower viscosity. 

Dyestuffs. The use of thiophene-based dyestuffs has been largely the result of the access of 2-amino-3-substituted thiophenes via new cycHzation chemistry techniques (61). Intermediates of type (8) are available from development of this work. Such intermediates act as the azo-component and, when coupled with pyrazolones, aminopyrazoles, phenols, 2,6-dihydropyridines, etc, have produced numerous monoazo disperse dyes. These dyes impart yeUow—green, red—green, or violet—green colorations to synthetic fibers, with exceUent fastness to light as weU as to wet- and dry-heat treatments (62-64). 

Table 4. Disperse Red Dyes, 2-Substituted l-Amino-4-hydroxyanthraquinones...

Substituted Anthraquinones. Commercially important blue disperse dyes are derived from 1,4,5,8-substituted anthraquiaones. Among them, diaminodihydroxyanthraquiaone derivatives are most important in view of their shades and affinity. Representative examples are Cl Disperse Blue 56 [31810-89-6] (11) Cl 63285) (126), and Cl Disperse Blue 73 (113) (115). Introduction of a halogen atom ortho to the amino group improves affinity and lightfastness. 

A Substituted-l-Amino-4-hydroxyanthraquinones. These dyes show good affinity and hghtfastness and give violet to blue shades. However, the sublimation fastness is in general not satisfactory. An example is Cl Disperse Blue 72 [81-48-1] (117) (Cl 60725), prepared from leucoquinizarin and -toluidine. 

Dispersion The movement of aggregates of molecules under the influence of a gradient of concentration, temperature, and so on. The effect is represented hy Tick s law with a dispersion coefficient substituted for molecular diffusivity. Thus, rate of transfer = —Dj3C/3p). 

Dispersion model is based on Fick s diffusion law with an empirical dispersion coefficient substituted for the diffusion coefficient. The material balance is... 

Hazardous chemicals or mixtures may be replaceable by safer materials. These may be less toxic per se, or less easily dispersed (e.g. less volatile or dusty). Substitution is also applicable to synthesis routes to avoid the use of toxic reactants/solvents or the production, either intentionally or accidentally, of toxic intermediates, by-products or wastes. 

In general, the reaction between a phenol and an aldehyde is classified as an electrophilic aromatic substitution, though some researchers have classed it as a nucleophilic substitution (Sn2) on aldehyde [84]. These mechanisms are probably indistinguishable on the basis of kinetics, though the charge-dispersed sp carbon structure of phenate does not fit our normal concept of a good nucleophile. In phenol-formaldehyde resins, the observed hydroxymethylation kinetics are second-order, first-order in phenol and first-order in formaldehyde. 

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