Silicone surfactants compared

The behaviour of M2D-C3-0-(E0)ra-CH3 over time (4 weeks) has been monitored by FIA-APCI-MS in the presence of Al(OH)3, CaC03 (calcite), FeO(OH) (goethite), Fe203 (hematite), halloysite, illite, kaolinite, sand, pumice, talc and Ti02 (anatase), and provides some useful comparative information regarding silicone surfactant behaviour in the presence of various solid media [10]. In general, the results indicated a dependence of parent molecule recovery on pH, with lower recoveries obtained with more extreme pH values (i.e. halloysite and sand, pH 3.7 and 4.8, respectively), consistent with the known pH instability of trisiloxanes under aqueous conditions [3,11,12,16]. In particular, the loss of the parent molecule was most rapid in the presence of the clay, halloysite, and is consistent with other reports of acceleration of silicone hydrolysis in the presence of acid clays [23-25]. Comparison of the recovery of M2D-C3-0-(E0) -CH3 in the presence of halloysite, kaolinite and illite clays (0.1%, 10 mg g-1) by FIA-APCI-MS is presented in Fig. 5.5.1 [10],... 

The surfactant properties of polymeric silicone surfactants are markedly different from those of hydrocarbon polymeric surfactants such as the ethylene oxide/propylene oxide (EO/PO) block copolymers. Comparable silicone surfactants often give lower surface tension and silicone surfactants often self-assemble in aqueous solution to form bilayer phases and vesicles rather than micelles and gel phases. The skin feel and lubricity properties of silicone surfactants do not appear to have any parallel amongst hydrocarbon polymeric surfactants. 

Figures 1.22,1.23, and 1.24 further demonstrate the reduction of FTC values that can be achieved in the back formulations when the new catalyst and experimental silicone surfactant technologies are utilised. At a 90 and 100 second TPR, control formulation V produces good quality foam. When the TPR is increased above 100 seconds foam tightness and surface quality issues arise with the control formulation. Formulations VI, VII and Vin yield good quality foam at all TPR cycle times used in this study. As in the cushion formulation, these lower FTC delta values demonstrate how these newly developed additives enhance crush-out capabilities. Furthermore, this effectively illustrates that the TPR window can be extended as compared to the control formulation.

Tables 1.6 and 1.7 provide the physical property comparison for all formulations I-Vin at a 90 second TPR time. The data clearly demonstrates that physical properties are maintained, and in several cases improved, compared to the control formulations. For example, airflow can be improved by as much as 20% as compared to both cushion and back control formulations, when using Dabco BL-53 and experimental silicone surfactants...

X-N1586/X-N1587 in combination (formulations IV and VIII). Furthermore, Japanese wet set values [6] can be improved by 5 to 8% with the Dabco BL-53, and experimental silicone surfactants X-N1586 and X-N1587. Wet set values are improved nearly 20% when the two additives are utilised in combination as evidenced by Formulations IV and VIII. Equally important, humid aged compression set, tensile and tear physical properties display a positive improvement trend as compared to the control formulations. 

A characteristic of the early neutron reflectivity studies of nonionic surfactant adsorption was some variability in the pattern of adsorption. This was investigated in more detail and more systematically by McDermott et al. [55], who compared the adsorption of Ci2E6 onto a range of different substrates, amorphous silica, crystalline quartz, and the oxide layer on a silicon single crystal. The adsorbed surfactant was found to form a bilayer with an overall thickness 49 4 A, with a structure similar to that determined in the previous studies (see Fig. 4). 

More convenient objects for the study of Cm(Caf) dependence have been found to be the low molecular compounds with relatively good solubility (compared to the silicon oil), for example, fatty alcohols, acids and hydrocarbons [48,55]. The experiments commented below were performed with these antifoams. First of all the Cm of films in the absence of an antifoam was determined by gradually increasing the surfactant concentration. Then small doses of the antifoam were introduced in a solution with surfactant concentration slightly above Cm, until the formation of black spots became impossible. At the same time the concentration of antifoam saturation in the solution was fixed. Table 9.2 presents the antifoam concentrations at which black spot formation in microscopic foam films is inhibited. 

A system, which does offer a considerable potential is that described by Podczeck (164). Here the excipient is colloidal silicon dioxide plus a surfactant, which appears to be able to provide formulations with high drug loading and pellets that are round and have a narrow size distribution (compare the pellets in Figure 4 with those in Figure 3). 

Summary Organomodified trisiloxanes show remarkable surface activity. Thus they can be used as additives in detergents, foaming agents or agrochemicals. However, this class of compounds has a limited range of applications, since it is susceptible to hydrolytic decomposition in aqueous solution. The hydrolysis occurs at the silicon-oxygen-bonds present within the molecules. Recently, a new class of silane surfactants free of Si-0-bonds has been developed. These silane surfactants proved to be hydrolytically stable even under extreme pH. Furthermore they exhibit surfactant properties comparable to those typical of trisiloxane surfactants. 

We have compared these theoretical predictions of the low-frequency modulus to experimental measurements on compressed emulsions and concentrated dispersions of microgels [121]. The emulsions were dispersions of silicone oil (viscosity 0.5 Pas) in water stabilized by the nonionic surfactant Triton X-100 [102, 121]. The excess surfactant was carefully eliminated by successive washing operations to avoid attractive depletion interactions. The size distribution of the droplets was moderately polydisperse with a mean droplet diameter of 2pin. The interfacial energy F between oil and water was 4mJ/m. The contact modulus for these emulsions was thus F 35 kPa. The volume fraction of the dispersed phase was easily obtained from weight measurements before and after water evaporation. Concentrated emulsions have a plateau modulus that extends to the lowest accessible frequencies, from which the low-frequency modulus Gq was obtained. Figure 11 shows the variations of Gq/E"" with 0 measured for the emulsions against the values calculated in the... 

Synthesis of organized mesoporous aluminas is based on the same approaches as those successfully used for the synthesis of mesoporous molecular sieves ( anionic , cationic , and neutral ) using aluminum alkoxide as the source of aluminum and in the absence of any silicon source. In contrast to the synthesis of siliceous MCM-41, the cationic route to organized mesoporous aluminas using hexadecyltrimethylammonium cations is the least applied and understood. Cabrera et al. [68] described the possibility to tailor the pore dimensions from 3.3 to 6.0 nm by modifying the ratio of surfactant, water and triethanolamine however, this synthesis route seems to be less reproducible compared with anionic and neutral routes. 

The template removal step, needed to achieve porous materials, is one of the most critical points. In contrast to silica, other compositions are usually more sensitive to thermal treatments and calcination can result in breakdown of the mesostructures. Hydrolysis, redox reactions, or phase transfonnarions to the thermodynamically preferred denser crystalline phases account for this lower thermal stability. Many of the transition metal-based mesostruetured materials synthesized in the presence of cationic surfactants collapse during thermal treatments. The poor thermal stability observed could be due to the different 0x0 chemistry of the metals compared to silicon. Several oxidation states of the metal centers may be responsible for oxidation and/or reduction during calcination. In addition, incomplete condensation of the framewoik is possible. 

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