Hexadecane INDEX

The relationship between film thickness of hexadecane with the addition of cholesteryl LCs and rolling speed under different pressures is shown in Fig. 25 [50], where the straight line is the theoretic film thickness calculated from the Hamrock-Dowson formula based on the bulk viscosity under the pressure of 0.174 GPa. It can be seen that for all lubricants, when speed is high, it is in the EHL regime and a speed index 4> about 0.67 is produced. When the rolling speed decreases and the film thickness falls to about 30 nm, the static adsorption film and ordered fluid film cannot be negligible, and the gradient reduces to less than 0.67 and the transition from EHL to TFL occurs. For pure hexadecane, due to the weak interaction between hexadecane molecules and metal surfaces, the static and ordered films are very thin. EHL... 

Let us first consider the various compound-specific parameters in Eq. 11-3. In Chapters 4 to 7, we used the refractive index to quantify the dispersive vdW properties of a given compound [i.e., vdW( < (nf - 1)/( , + 2)], see Section 3.2]. We also noted that other parameters such as the air-hexadecane partition constant, K, would have been more appropriate to describe vdW, however, due to lack of experimental Kiah values, we have chosen not to do so here. Instead, we use the... 

Table 4 Polydispersity index as a function of initiator concentration and sonication time, with hexadecane as costahUizer and MMA as monomer ([140])...

Hexadecane level (gm) Particle diameter d (nm) Polydispersity index... 

Figure 15.9 Improved resolution due to double-pore volume. Conditions sample, dodecane and hexadecane column(s), 30cm x7.8mm i.d. gel, pStyragel 100 A mobile phase, 1 ml min toluene refractive index detector.

Table 14.1 Composition, HLB temperature (Phlb) droplet radius r and polydispersity index (PI) for the system water-C,jE04-hexadecane at 25 C.

The results with isohexadecane are summarised in Table 14.2. As with the hexadecane system, the droplet size and polydispersity index were decreased with increases in surfactant concentration. Nanoemulsions with droplet radii of 25-80run were obtained at 3-8% surfactant concentration. It should be noted, however, that nanoemulsions could be produced at lower surfactant concentration when using isohexadecane, when compared to results obtained with hexadecane. This could be attributed to the higher solubility of isohexadecane (a branched hydrocarbon), the lower HLB temperature, and the lower interfacial tension. 

Dispiro-l,2,4,5-tetraoxanes (45 1-3) were prepared with the intact peroxide functional group and tested for antimalarial activity [51], Dispiro-1,2,4,5-tetraoxanes, 1(5), 10( )-dimethyl-7,8,15,16-tetraoxodispiro[5,2,5,2]hexadecane (45 3) was as active as artemisinin, both in vitro and in vivo. Based on the resistance index (IC50(W-2)/IC5o(D-6)), 2,4,1 l,13-tetramethyl-7,8,15,16 tetraoxodispiro[5,2,5,2]hexadecane... 

Recently Loci, Mayhew, and Williamson have examined the extension of the principle of congruence to ternary alkane mixtures. As shown in Figure 10, the enthalpy of mixing of mixtures of alkanes of end-point indices 6 and 16 is very nearly independent of whether or not the end-point index (w = 16) is that of a pure substance (n-hexadecane) or of a mixture (n= 13 + = 19, X = 0.5). 

Hexadecane was studied as a model non-polar lubricant with a relatively high surface energy (y = 27.4 mJ/m at 20°C). The fluorescent probe was NBD dihexadecylamine at 5 ppm. The surface under study was a disk of sapphire (a-AljOj 001 ) with a rms roughness of 0.4 nm as measured by x-ray reflectivity. Sapphire has a high refractive index and the surface can be chemically modified. Three surface... 

Tab. 9.1. Composition, HLB temperature (Thlb)i droplet radius rand polydispersity index (pol.) for the system water—Ci2E04—hexadecane at 25 °C.

The stable free radical polymerization technique is characterized by the growing polymer chains that are reversibly capped by a stable free radical [e.g., 2,2-tetramethyl-l-piperidynyloxy nitroxide (TEMPO)]. For example, stable polystyrene dispersions were prepared by the stable free radical polymerization of styrene conducted in miniemulsion polymerization at 135 C [62]. Sodium dodecylbenzene sulfonate, hexadecane, and potassium persulfate/ TEMPO were used as the surfactant, costabihzer, and initiator system, respectively. Prodpran et al. [63] studied the styrene miniemulsion polymerization stabilized by Dowfax 8390 and hexadecane and initiated by benzoyl peroxide at 125 °C. A molar ratio of TEMPO to benzoyl peroxide equal to 3 to 1 resulted in polystyrene with the lowest polydispersity index (1.3) of polymer molecular weight distribution. 

Working Standards—For working standard hydrocarbons, reasonably well purified samples of n-hexadecane, fra/i -decahydronaphthalene, and 1-methylnaphthalene may be used. Their exact values are determined by comparison with standard samples of the same hydrocarbons having certified values of refractive index. 

Measure the refractive index of API Standard n hexadecane and 1-methylnaphthaIene at the test temperature following the procedure described in Section 12. 

Construct a calibration curve for use at the chosen test temperature. Plot the difference between the observed refractive index for n-hexadecane and its certified value along the ordinate against the refractive index level along the abscissa. Also plot the difference between the observed and certified refractive indices for 1-methylnaphthalene in the same manner. Draw a straight line from the point representing the deviation found for n-hexadecane to zero at the certified refractive index of trans-decahydronaphthalene. 

If it is desired to measure the refractive index of samples at a temperature other than 80 or lOO C, obtain calibration data by repeating 11.1 to 11.4 at this desired temperature. Determine the refractive indices for the API Standard compounds, n-hexadecane, tran.r-decahydronaph-thalene, and 1-methyInaphthalene at the desired temperature by plotting the certified refractive indices at 20, 25, 30, 80, 100 C against temperature and drawing a smooth curve between the points. 

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