Short-chain dispersants

Such short-chain dispersants cannot adopt a random coil configuration they will be more or less linear molecules no matter the ability of the polymer to solvate the chains. In fact, molecules like stearic acid on calcium carbonate pack together so tightly that there is no possibility for the polymer to penetrate between e chains and interact with them anyway. Thus, it is found that in reality, short-chain dispersants are often rather efficacious and need not be tuned to exactly match the polymer they are used in. The length of the chain can be tuned but in reality, stearate groups are so inexpensive that other types cannot compete in any but the most specialized applications. Similarly, in theory, the best dispersant tail is one with a polarity matched closely to that of the matrix polymer. However, in practice, hydrocarbon tail types predominate as they are available and at low cost. 

Short-Chain Organics. Adsorption of an organic dispersant can reduce polarizabiHty attraction between particles, ie, provide semisteric stabilization, if A < A.p < A or A < A.p < A (T = dispersant) and the adsorption layer is thick. Adsorption in aqueous systems generally does not foUow the simple Langmuir profile because the organic tails on adsorbed molecules at adjacent sites attract each other strongly. 

Sulfated Acids, Amides, and Esters. Reaction with sulfuric acid may be carried out on fatty acids, alkanolamides, and short-chain esters of fatty acids. The disodium salt of sulfated oleic acid is a textile additive and an effective lime soap dispersant. A typical sulfated alkanolamide stmcture is CiiH23C0NHCH2CH20S03Na. Others include the sulfates of mono and diethanolamides of fatty acids in the detergent range. The presence of... 

In Sec. 3 our presentation is focused on the most important results obtained by different authors in the framework of the rephca Ornstein-Zernike (ROZ) integral equations and by simulations of simple fluids in microporous matrices. For illustrative purposes, we discuss some original results obtained recently in our laboratory. Those allow us to show the application of the ROZ equations to the structure and thermodynamics of fluids adsorbed in disordered porous media. In particular, we present a solution of the ROZ equations for a hard sphere mixture that is highly asymmetric by size, adsorbed in a matrix of hard spheres. This example is relevant in describing the structure of colloidal dispersions in a disordered microporous medium. On the other hand, we present some of the results for the adsorption of a hard sphere fluid in a disordered medium of spherical permeable membranes. The theory developed for the description of this model agrees well with computer simulation data. Finally, in this section we demonstrate the applications of the ROZ theory and present simulation data for adsorption of a hard sphere fluid in a matrix of short chain molecules. This example serves to show the relevance of the theory of Wertheim to chemical association for a set of problems focused on adsorption of fluids and mixtures in disordered microporous matrices prepared by polymerization of species. 

Anionic pol5Tnerizations make the molecular weight standards that are used to calibrate size-exclusion chromatographs. Equation (13.38) predicts PD = 1.001 at In = 1000. Actual measurements give about 1.05. The difference is attributed to impurities in the feed that cause terminations and thus short chains. Also, the chromatograph has internal dispersion so that a truly monodisperse sample would show some spread. Even so, a PD of E05 is extremely narrow by pol5Tner standards. This does not mean it is narrow in an... 

The first situation applies for the short-chain alcohols, acetone, or ether. After their evaporation, the drug remains finely dispersed on or in the skin at 100% concentration. 

In the Figure 4 the values of the disoersion obtained from a computer experiment are compared with Poisson and linear dispersions. It can be seen from that figure that the true distribution is much wider than the Poisson distribution and that the width is increased with an increase in chain length. In the initial stage, the dispersion follows the linear approximation. For short chains at high degrees of cross-linkinc the distribution becomes narrower due to the accumulation of chains with many cross-linkages /close to the maximum value/7 and the dispersion tends to that of a Poisson. 

In fact, even in pure block copolymer (say, diblock copolymer) solutions the self-association behavior of blocks of each type leads to very useful microstructures (see Fig. 1.7), analogous to association colloids formed by short-chain surfactants. The optical, electrical, and mechanical properties of such composites can be significantly different from those of conventional polymer blends (usually simple spherical dispersions). Conventional blends are formed by quenching processes and result in coarse composites in contrast, the above materials result from equilibrium structures and reversible phase transitions and therefore could lead to smart materials capable of responding to suitable external stimuli. 

When surfactant molecules are dissolved in organic solvents, the head groups cluster together and the hydrocarbon chains point into the bulk phase, forming reverse micelles. If water is trapped in the area of the head groups, the system is termed a microemulsion. Sometimes, a short chain alcohol (e.g. hexanol) is added to aid dispersion. 

B ZDDP + polyisobutylene succinimide dispersant + calcium carbonate-phenate [Ca] = 890 ppm Composed of inorganic, low molecular weight amorphous short chain ortho-(P043 ) and pyro- (P2074 ) phosphates ( 20% of zinc was replaced by calcium in phosphate tribofilm)... 

The tribofilms formed from a ZDDP were composed of long chain phosphates with zinc as a cation but with a mixture of a ZDDP + detergent and ZDDP + dispersant, only short-chain phosphates with zinc and calcium as cations are formed in the presence of a sulfide (Barcroft and Park, 1986 Willermet et al., 1995a). 

The engine oil containing ZDDP and carbonate-detergents RMs formed orthophosphate and pyrophosphate tribofilms. In the presence of detergent and dispersant only short-chain phosphates were observed (Willermet et al., 1991, 1992 and 1997 Yin et al., 1997b). 

The classical thermodynamic and kinetic model is that of a rigid sphere impenetrable by water. A spherical geometry has been observed in many polysaccharide systems, notably hyaluronic acid-protein complexes (Ogston and Stainer, 1951), dispersed gum arabic (Whistler, 1993), and spray-dried ungelatinized starch granules (Zhao and Whistler, 1994). Spherulites of short-chain amylose were obtained by precipitation with 30% water-ethanol (Ring et al., 1987), and spherulites of synthetic polymers were obtained... 

Pigment and filters Poly substituted phenol ethoxylates Phosphate esters Short chain amine EO/PO co-polymers Lignin sulphonates Wetters and dispersants... 

Mlcroemulslons are related to micellesThe most common, the four component mlcroemulslons, are constructed from a hydrocarbon, a surfactant, a short chain alcohol (cosurfactant) and water. When the hydrocarbon component present is significantly larger than the water component the mlcroemulslon Is generally a water-ln-oll (w/o) mlcroemulslon. Figure Id. This designation arises by virtue of the fact that the water is present In the form of spheres. Invisible to the naked eye (250 to lOOoR In diameter), dispersed throughout the hydrocarbon continuum. The surfactant and cosurfactant stabilize these water-rich droplets and help render them thermodynamically stable. These systems are optically transparent and can contain up to 0.3Xn ... 

ANEDCO AC-163 is a versatile basic intermediate which can be further modified by reacting with dimer-trimer acids to obtain an excellent film persistent-corrosion inhibitor. Various surfactants may be added to obtain improved water dispersibility. ANEDCO AC-163 may be reacted with a short chain organic acid such as acetic acid, hydroxy acetic acid, etc. to form a water-soluble corrosion inhibitor. 

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