Hexadecane, immersion

The FTE SAMs have a good hydrophobic property. Ohio et al. [36] have compared the variation of contact angles with immersing time in a neat FTE and a 100 mM FTE solution. The contact angles of water and hexadecane increased to about 110° and 73° from the initial value 76° and 36°, respectively, after 24 h immersion. Their works also indicate that the adsorption rate in 100 mM FTE solution is slightly faster than that in neat FTE. 

Add 2 mL of hexadecane and 2 boiling stones to the 500-mL distillation flask containing the combined isooctane extracts, and attach the flask to a suitable vacuum distillation assembly. Evacuate the assembly to about one-third atmosphere, then immerse the flask in a steam bath, and distill the solvent. When isooctane stops dripping into the receiver, turn off the vacuum, wash down the walls of the flask with 5 mL of isooctane added through the top of the distillation head, then replace the thermometer and again evacuate. The isooctane should distill over in about 1 min. At the end of this distillation, add another 5-mL portion of isooctane, and repeat the stripping procedure. 

The change in nature of the oxidized surface can be followed with immersion liquids other than water. By increasing the oxygen content of a carbon black (Le. Spheron 6) up to 12%, Robert and Brusset (1965) obtained an increase of the energy of immersion in methanol from 140 to as much as 390 mJ nT2 (practically the same ratio as that observed with water), whereas the energy of immersion in n-hexadecane remained nearly constant, around 100 mJ m-2. 

Figure 2.20. DiiTerences between pairs of enthalpies of wetting, obtained from the temperature dependence of the adsorption (open circles) and from immersion calorimetry (closed circles), (a) hexane + hexadecane (b) pentane + decane. Adsorbent Graphon. (Source as in fig. 2.19.)...

The suggested formation of a regular upper surface of exposed methyl groups even before the surface is largely covered with acid molecules would account for the rapid rise of contact angle with short immersion times observed for the behenic acid films from hexadecane. 

A few studies investigate the coating ITO with organic monolayers of amphiphilic molecules [318-322]. Stearic and archidic acid [318] solutions were made by dissolution in hexadecane at 40 °C. The solutions were kept for 24 h at 30 °C during ITO sample immersion. After the solutions cooled to ambient temperature, the samples were rinsed with hexane and blown dry with N2. Bifunctional HS(CH2)i5COOH was adsorbed from 0.5 mM ethanol solution at room temperature. These molecules were found to form stable and ordered monolayers on ITO. HS(CH2)i5COOH molecules can be utilized to generate a thiol-terminated SAM on ITO [318]. 

Napier and Thorp [319] developed a nucleic acid detection system based on the catalytic oxidation of guanine residues by a Ru(bpy)3 + mediator. Monolayers were self-assembled by immersion of ITO in 5 mM 1,12-dodecanedicarboxylic acid in hexadecane for 36-48 h. The electrodes were thoroughly rinsed with hexane to remove any physically adsorbed molecules. 

Latex (emulsion) adhesives. In contact with water, adhesive bonds with latex adhesives may release surfactants, which will have the effect of lowering surface tension and changing the thermodynamic work of adhesion. Some latices based on copolymers of vinyl acetate were dried to give films which were then immersed in small quantities of water. The surface tensions (/w) fell from 72.8 mN m to values in the range 39-53 mN m in the first hour and then remained fairly static [76]. Measurements of interfacial tensions against n-hexadecane showed the dispersion components of surface tension remained essentially constant but polar components were reduced into the range 6-20 mN m ... 

In the Falex Multi-Specimen Friction Wear Test instrument, the ball and disk are enclosed in a cup, which is then filled with 50 mL of lubricant before the test, so as to completely immerse the ball-and-disk assembly in the lubricant. As described below, the lubricant is a solution with a known concentration of vegetable oil or methyl ester in hexadecane. Friction was measured at room temperature (25°C 2 C) for 15-30 min at 6.22 mm/s (5 rpm) and 181.44-kg load. The temperatures of the specimen and lubricant increased by only l°C-2 at the end of each test period. Two tests were conducted with each lubricant sample using a new set of ball-and-disk specimens for each test. The COFs from the duplicate tests were then averaged to obtain the COF of the lubricant being tested. In general, the standard deviation of the COFs from the duplicate runs was less than 5% of their mean. 

Stress-strain measurements on unswollen samples and those partially swollen with hexadecane were carried out at 33.6°C. Samples swollen to equilibrium in decane were submerged in the liquid (plus. 05% antioxidant) in a cylindrical container at 35°C. Partially swollen samples were prepared by immersing specimens in the diluent for a limited time and allowing 48 h for uniform distribution of the diluent throughout the specimen. The amount of diluent was determined by weighing and the volume fraction of polymer calculated from the known specific volumes of polymer and liquid, additivity of volumes being assumed. 

Pit and his co-workers found evidence for slip even for hexadecane on clean sapphire, with b = 175 nm. This slip was prevented by an inhomogeneous coating of FDS. When the sapphire was coated with an OTS layer, slip length increased Xo b = 400 nm. When the clean sapphire was tested with stearic acid solution in hexadecane, the extent of slip increased with time of immersion of the sapphire to reach b = 350 nm. 

The surface area of porous solids was determined from the heat of Immersion method using calorimetry. The heat of Immersion of different solid powders in n-hexadecane was measured. These data agreed with the BET method. 

Fig. 1. Heat of Immersion (h ) vs. surface area (m /g from BET data) of different powders (fluld= n-Hexadecane).(25 C).

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