Oleophobic additive

Chem. Descrip. Alkyltrialkoxy silane with oleophobic additive Uses Water repellent tor concrete, brick, and nat. stone Features Resist, to automotive fluids, water intnision, chloride ion screening low VOC... 

For many organic compounds that accumulate in lipids, bio accumulation potential can be estimated from the Kow. Since perfluoroalkyl compounds are inherently oleophobic, and do not partition preferentially to lipid rich tissues [67], the K0w is not a useful predictor of bioaccumulation and direct evidence derived from the laboratory or field is required. Additionally, tissue concentrations of perfluoroalkyl substances should never be lipid normalized. The dietary accumulation, bioconcentration, and biomagnification potential of various perfluoroalkyl carboxylates and sulfonates have been assessed in the laboratory and in the Great Lakes food web (Table 4). 

Adsorbed films of ethykriethoxysilane and vinyltriethoxy-silane were formed on silica and alumina by retraction from hydrocarbon solution and their wettabilities and water-stabilities determined. The vinyltriethoxysilane films were generally more oleophobic, more hydrophobic and more resistant to contact with water than the films formed by the ethyl analog. Neither adsorbate formed stable films on a-alumina. The addition of low molecular weight organic acids or bases to the adsorbate solution resulted in both the ethyl and vinyl compound forming hydrophobic and water-stable films on silica and ot-alumina. Films of p-chloro-phenyl-ft-ethyltrichloro, -trimethoxy, and -triethoxysilane were also studied and found to be water-stable and to have wettabilities characteristic of a surface comprised of closely-spaced p-chlorophenyl groups. 

Timmons [20] carried out similar experiments with radioactive stearic acid on surfaces of chromium, nickel, 304 stainless steel and 416 stainless steel, in addition to iron. The films on nickel and chromium showed slightly less oleophobic behavior to a drop of methylene iodide and also had a slightly less compact packing (Table 10-6). The course of... 

In addition to patterned hydrophiUcity/hydro-phobicity, there have been reports of patterned phiUc/phobic surfaces for other liquids, such as oils [8]. Due to the geometry-dependent directionality of oleophobicity, patterned oleophiUc/ oleophobic surfaces tend to only work when the liquid is introduced from a certain direction, such... 

Owens et al. (2008) developed a method to produce highly hydrophobic and oleophobic rtylon-cotton materials. This method involves a microwave-induced attachment of perfluoroalkylsilanes on to suitable substrates. The authors noted that the substrates should have primary alcohol or primary/secondary -NH-moieties. The fluoroalkyl chains can be attached to the -OH or -NH- sites via siloxane or silazane linkages. Heat or microwave radiation is employed to speed up the attachment process. According to the authors, the addition of a base was found to have a similar effect on the attachment process. ... 

The reason for this behaviour is that the surfactant molecule contains two structurally distinct parts, one of which is hydrophilic while the other is hydrophobic. Oil-soluble surfactants have an oleophilic and an oleophobic part. In the great majority of surfactants, the hydrophobic part is a hydrocarbon chain, which usually has an average length of 12 to 18 carbon atoms and may include an aromatic ring. A single molecule in aqueous solution seeks the surface, because its hydrocarbon tail is repelled by the water, and it tends to remain there, with the hydrophobic part above the surface and the hydrophilic part below, i.e. in the water phase. Further molecules seek the surface or the walls of the vessel until both are full, at which point further additions result in the formation of micelles, which are clusters of molecules arranged with the hydrophobic parts towards the centre and the hydrophilic parts on the outside. 

Copolyoxetanes. Structure 10.2 shows amphiphilic copolyoxetanes having fluorous A (hydrophilic/oleophobic) and poly(ethylene glycol) (PEG-like) hydrophilic B side chains. These copolyoxetanes are remarkable in that random or block architectures may be obtained depending on the order of addition of monomers [17, 39], The discussion below focuses on P[A-co-B] 2 with 3F and ME3 pendant groups. Table 10.1 provides compositions, M, and modulated differential scanning calorimetry... 

An important aspect of the concept of roughening step followed by chemical modification is that the delicate topography of a nano-/micro-rough surface must not be affected by, e.g., the deposition of hydrophobic or oleophobic finish. Therefore, grafting or thin-layer deposition processes are more favorable. Physically driven processes such as plasma-based or UV induced grafting have the additional advantage of minimal use of chemicals for surface modification. 

---