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Surfactant A “surface-active agent

Surfactant A surface-active agent a substance that has the abil-... [Pg.584]

Surfactant. A surface active agent that reduces the surface tension of water and aqueous solutions, reduces the interfacial tension between two liquids, or reduces the interfacial tension between a liquid and a solid. [Pg.658]

Surfactant. A surface active agent a chemical which reduces the surface tension of a liquid, and so improves the wetting of a surface. They are useful in dispersing powders, when surfactants adsorbed on particle surfaces produce repulsive forces between the particles when the adsorbed layers overlap (steric hindrance.)... [Pg.317]

Internal surfactant antistats ate physically mixed with the plastic resin prior to processing. When the resin is melted, the antistat distributes evenly in the polymer matrix. The antistat usually has some degree of solubiUty in the molten polymer. However, when the polymer is processed (extmded, molded, etc) into its final form and allowed to cool, the antistat migrates to the surface of the finished article due to its limited solubiUty in the solidified resin. The molecule of a surface-active agent is composed of a polar hydrophilic portion and a nonpolar hydrophobic portion. The hydrophilic portion of the surfactant at the surface attracts moisture from the atmosphere it is the moisture that has the static dissipative effect. [Pg.297]

The second type is a stable dispersion, or foam. Separation can be extremely difficult in some cases. A pure two-component system of gas and liquid cannot produce dispersions of the second type. Stable foams can oe produced only when an additional substance is adsorbed at the liquid-surface interface. The substance adsorbed may be in true solution but with a chemical tendency to concentrate in the interface such as that of a surface-active agent, or it may be a finely divided sohd which concentrates in the interface because it is only poorly wetted by the liquid. Surfactants and proteins are examples of soluble materials, while dust particles and extraneous dirt including traces of nonmisci-ble liquids can be examples of poorly wetted materials. [Pg.1441]

Modem commercial detergents are mixtures. Their most important component is a surfactant, or surface-active agent, which takes the place of the soap. Surfactant molecules are organic compounds with a structure and action similar to those of soap. A difference is that they typically contain sulfur atoms in their polar groups (4). [Pg.442]

A surfactant is a surface-active agent that is used to disperse a water-insoluble drug as a colloidal dispersion. Surfactants are used for wetting and to prevent crystal growth in a suspension. Surfactants are used quite extensively in parenteral suspensions for wetting powders and to provide acceptable syringability. They are also used in emulsions and for solubilizing steroids and fat-soluble vitamins. [Pg.394]

What is a surface-active agent (or a surfactant) Why is it often referred to as an amphipathic molecule ... [Pg.348]

This is a very important equation. It directly tells us that when a solute is enriched at the interface (T > 0), the surface tension decreases when the solution concentration is increased. Such solutes are said to be surface active and they are called surfactants or surface active agents. Often the term amphiphilic molecule or simply amphiphile is used. An amphiphilic molecule consist of two well-defined regions One which is oil-soluble (lyophilic or hydrophobic) and one which is water-soluble (hydrophilic). [Pg.37]

Enhancement of the aqueous solubility by surfactants occurs as a result of the dual nature of the surfactant molecule. The term surfactant is derived from the concept of a surface-active agent. Surfactants typically contain discrete hydrophobic and hydrophilic regions, which allow them to orient at polar-nonpolar interfaces, such as water/air interfaces. Once the interface is saturated, th surfactants self-associate to form micelles and other aggregates, whereby their hydrophobic region are minimized and shielded from aqueous contact by their hydrophilic regions. This creates a discrete hydrophobic environment suitable forsolubilization of many hydrophobic compounds (Attwood and Florence, 1983 Li et al., 1999 Zhao et al., 1999). [Pg.256]

All of the samples prepared by centrifugation and the float-sink method were demineralized and milled to three micron diameter. The separations were conducted in the presence of a surface active agent, polyoxyethylene(23) lauryl ether, in cesium chloride solutions (14). The macerals were washed thoroughly to reduce the quantity of surfactant in the maceral to less than 500 ppm and the quantity of chloride ion in the wash water to below the limit detectable by precipitation with silver ion (14). [Pg.160]

A lew experimental data are available in the literature, namely those of Hull and Kitchener,4 and Fitzpatrick and Spielman.14 Hull and Kitchener observed a non-uniform distribution of the collected particles, which becomes more uniform when a surface active agent is present. Surfactants alter the nature of both collector and... [Pg.81]

A wettable powder formulation of a biological insecticide requires a surface active agent (surfactant). This allows... [Pg.181]

Surfactants or surface-active agents make up a special class of chemicals used in practically all industries. Surfactants may be of petrochemical or natural oils origin. This chapter discusses only those of vegetable oil origin, specifically those from coconut oil. [Pg.3023]

Multi-walled nanotubes can also be ultrasonically dispersed in a liquid and made soluble with a surface active agent (surfactant) to inhibit coalescence. The resulting suspension is drawn through a filter to remove smaller particles and the remaining material consists of reasonably purified intact nanotubes. The surfactant is then washed off [119]. [Pg.416]

The secondary solvents used for this purpose are a surface-active agent or emulsifiers. Triton X-100 and Triton N-101 are nonionic surfactants commonly used in laboratory-prepared scintillation cocktails. Anionic surfactants give better sampleholding capacities than the nonionic surfactants for certain types of salt solutions. [Pg.190]

If a suspension is to be produced by a dispersion technique (as opposed to precipitation techniques), surfactants may be used in the formulation to aid dispersion of the solid particles in the liquid. This is particularly important if the powder is not readily wetted by the liquid vehicle. Surfactants can reduce the interfacial tension between the solid particles and the liquid vehicle. The advancing contact angle is reduced, and wetting of the solid particles promoted. Such a system is said to be deflocculated. The inclusion of a surface-active agent to improve powder wettability can often improve the bioavailability of the formulation. [Pg.3589]

Increasing surfactant concentrations in the aeration cell has been found to decrease bubble diameter, bubble velocity, axial diffusion coefficient, but increase bubble s surface-to-volume ratio, and total bubble surface area in the system. The effect of a surface-active agent on the total surface area of the bubbles is also a function of its operating conditions. The surfactant s effect is pronounced in the case of a coarse gas diffuser where the chances of coalescence are great and the effectiveness of a surface-active solute in preventing coalescence increases with the length of its carbon chain. [Pg.97]

A surface-active agent (or surfactant) is a substance that lowers the surface or interfacial tension of the medium in which it is dissolved. Surfactants have a characteristic molecular structure consisting of hydrophobic and hydrophilic groups. This is known as an amphipathic structure, and causes not only concentration of the surfactant at the surface and reduction of the surface tension of the solvent, but also orientation of the molecule at the surface with its hydrophilic group in the aqueous phase and its hydrophobic group oriented away... [Pg.145]


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