Adsorption energy, emulsifier

The emulsifier adsorption energy (S) was calculated from the isotheim of the Interface surface tension, obtained by means of a stalagmometer with automatic recording of the number of drops. The Langmuir equation was used for calculations ... 

Formally the monomer polarity is not nearly sufficient to explain the differences in the adsorption energies of a given emulsifier on the water-alkylacry-lates interfaces (5) according to (21) the dipole moments of lower alkylacrylates have practically identical values. It appears possible that polcu ity of the interface itself is significant here this polarity increases as the monomer solubility in water increases from BA to HA the decrease of the free energy of the Interface, caused by it, results in its turn in decreased adsorption energy of emulsifier. 

Figure 2 shows similar Isotherms for ethylacry-late, obtained from the adsorption data for various emulsifiers. It is seen that these Isotherms considerably differ. The calculated values of the adsorption energy for different emulsifiers on the ethylacrylate -water Interface (T 293 K) are listed in Table II. 

It follows from the results obtained that the factors determining the adsotption value of a given surfactant at the water interface with the monomer and with the corresponding polymer are the same. Since with the increase in the adsorption energy on the emulsifier-monomer interface, the... 

The obseirved correlation can be explained by a stronger dependence of particle surface on emulsifier concentration when the energy of its adsorption increases. 

S6). It depended on the variation of the number of latex particles formed iV with temperature. Unfortunately, they have overlooked the fact that the particle growth rate fi which appears to the power —f in the Smith-Ewart expression for the number of latex particles formed coitains the propa gation rate constant which is temperature dependent. It has also recently been realized that another factor on which JV depends, the area occupied by a surfactant molecule at the polymer-water interface Og, is also temperature dependent- Dunn et al. (1981) observed that the temperature dependence of N in the thermal polymerization of styrene differed from different emulsifiers. It seems unlikely that the differences ran be wholly explained by differing enthalpies of adsorption of the emulsifiers and, if not, this observation implies that the energy of activation for thermal initiation of styrene in emulsion depends on the emulsifier used. Participation of emulsifiers in thermal initiation (and probsbly also in initiation by oil-soluble initiators) is most probably attributable to transfer to emulsifier and desorption of the emulsifier radical frcan the micelle x>r latex particle into the aqueous phase the rates of these processes are likely to differ with the emulsifier. 

The surfactants used for the preparation of disperse systems are seldom effective in maintaining the long-term physical stabihty (absence of flocculation and/or coalescence) of the formulation. This is due to their weak and reversible adsorption and lack of the presence of a high-energy barrier that prevents flocculation as a result of van der Waals attractions. For this reason, dispersants and emulsifiers of polymeric nature that are strongly and irreversibly adsorbed at the interface are required. In addition, these polymeric dispersant provide effective repulsive forces (referred to as steric repulsion) that overcomes the van der Waals attractions. The criteria for an effective dispersant are [1, 2] ... 

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