Surface finish Surfactants

Particulate soil is removed from fibres by a two-step process. First, a thin layer of wash liquid penetrates between the particle and the fibre surface, enabling surfactants to adsorb onto the particle surface (Fig. 7.1). Then, the particle becomes solvated and is transported away from the fibre and into the bulk of the wash liquid by mechanical action. Finishes that are hydrophilic (enhancing penetration of the fibre-soil interface) with low adhesion to soil under washing conditions should improve particulate soil release. Ablative or sacrificial finishes... 

The results indicate that some surfactants can definitely lead to better surface finish upon polish. Table 5 gives the average RMS (root mean square) values, Ra, of surface roughness obtained with the Dektak profilometer. The measurements are carried out on both the copper disks and 4 inch copper wafers. Dramatic improvements are noticed in polished surface uniformity when surfactants Brij 35 and SDS are employed in the slurry. The destabilizing... 

Styrenics/PA/PPE Styrenics/PBT Sulfonyl azide Surface finish Surface free energy Surface resistivity Surface tension Surfactant... 

Uses Antistat for PE, flexible PVC, plastisols softener for textile finishes emulsifier, flavoring agent, fonnulation aid, lubricant, release agent, softener, solvent, stabilizer, surfactant, surface-finishing agent. 

The final surface finish of leather goods is now commonly applied in the form of lacquerlike polymer coatings that can be apphed as emulsions and suspensions, using suitable surfactants, of course. Similar apphcations are found in the fur industry. 

Surfactant-type antistats find the widest use because of thek low cost and minimal effect on the mechanical properties of the plastic. Ease of use is another favorable aspect to surfactants. They can be mixed with the bulk of the plastic prior to processing or can be appHed to the surface of the finished plastic article as the need dictates. 

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. 

Alkanesulfonates are preferably used as an internal antistatic agent for plastics, but where incorporation into the polymer is not possible they can be applied to the surface of the finished article in the form of a 1 % aqueous solution of the surfactant by spraying or dipping [99]. 

Polyamide and polyester fibres are generally scoured using an alkyl poly(oxyethylene) sulphate and sodium carbonate. Some polyester qualities are subjected to a causticisation treatment with sodium hydroxide in the presence of a cationic surfactant to give a lighter fabric with a silkier handle [154,156]. This treatment involves etching (localised saponification) of the polyester surface and is broadly analogous to the S-finish used on triacetate fibres. The process has attracted considerable interest in recent years but its... 

The models of Fromherz and Dill allow the solubilization of hydrophobic solutes near the surface of the micelle and explain how these solutes (in addition to part of the hydrocarbon chains of the surfactants) can be in contact with the water when they are associated with the micelle. However, the debate concerning the structure of the clusters is not yet finished and research on the subject continues. 

Used industrially for the manufacture of phosphorus oxychloride, phosphorus pentachlor-ide, phosphites, organophosphorus pesticides, surfactants, gasoline additives, plasticizers, dyestuffs used as a chlorinating agent and catalyst. Used to prepare rubber surfaces for electrodeposition of metal. Used as an ingredient of textile finishing agents. 

In addition to studying the effect of the stabilizer molecular weight on the MMA dispersion polymerization, the effect of the stabilizer concentration was also analyzed. The concentration of poly(FOA) stabilizer was systematically varied while the amount of MMA was held constant at 21 w/v % in CO2 (Table 2). It was found that as little as 0.24 wt. % (based on monomer) is needed to stabilize the polymerization and give spherical particles. Additionally, excess surfactant could be washed from the finished particle surface with CO2, resulting in... 

Most non-polymeric antistatic finishes are also surfactants that can orient themselves in specific ways at fibre surfaces. The hydrophobic structure parts of the molecule act as lubricants to reduce charge buildup. This is particularly true with cationic antistatic surfactants that align with the hydrophobic group away from the fibre surface, similar to cationic softeners (see Chapter 3, Fig. 3.1). The main antistatic effect from anionic and non-ionic surfactants is increased conductivity from mobile ions and the hydration layer that surrounds the hydrophilic portion of the molecule since the surface orientation for these materials places the hydrated layer at the air interface. 

Although the formation of surface patterns via the Benard cell may occasionally be useful to form special finishes, usually it is desirable to eliminate the situation. Use of higher boiling solvents will retard evaporation rate and the cooling effect that changes surface tension and propels the vortex action. Increase in paint viscosity will inhibit the action, as will decrease in film thickness. Addition of a surfactant will provide a more uniform value of surface tension and also retard evaporation and thereby help to inhibit the vortex motion in cells. 

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