Polymer emulsification

Prior to this discovery, in 1954 Silberberg and Kuhn (62) were first to study the polymer-in-polymer emulsion containing ethylcellulose and polystyrene in a nonaqueous solvent, benzene. The mechanisms of polymer emulsification, demixing, and phase reversal were studied. Wetzel and Hocks discovery would then equate the pressure-sensitive adhesive to a polymer-polymer emulsion instead of a polymer-polymer suspension. Since the interface is liquid-liquid, the adhesion then becomes one type of R-R adhesion (35, 36). According to our previous discussion, diffusion is not operative unless both resin and rubber have an identical solubility parameter. The major interfacial interaction is physical adsorption, which, in turn, determines adhesion. Our previous work on the wettability of elastomers (37, 38) can help predict adhesion results. Detailed studies on the function of tackifiers have been made by Wetzel and Alexander (69), and by Hock (20, 21), and therefore the subject requires no further elaboration. 

Tara gum is used as an appetite suppressant and as a binding agent and disintegrating agent in compressed tablets. It is also used to thicken various cosmetic products such as lotions and creams [45-49]. Some excipients that improve solubility are hydrophilic solvents [50, 51] such as propylene glycol and polyethylene glycol. Hydrophobic solvents are vegetable oils, triacetin, and diethyl phthalate. Tara gum is used as polymer emulsifer with polysorbates and vitamin E [52, 53]. 

Vanderhoff JW, Mohamed S, Aasser El et al (1979) Polymer emulsification process. US Patent 4,177,177... 

Uses Wetting agent, dispersant, penetrant, emulsifier, detergent, solubilizer for textile wet processing, agric., cosmetic, industrial and household detergents, latex and polymers emulsification and post polymerization stabilization, wax/polishes bottlewashing compds. polyester resin emulsifiers demulsifiers for crude petrol./... 

Inversion ofMon cjueous Polymers. Many polymers such as polyurethanes, polyesters, polypropylene, epoxy resins (qv), and siHcones that cannot be made via emulsion polymerization are converted into latices. Such polymers are dissolved in solvent and inverted via emulsification, foUowed by solvent stripping (80). SoHd polymers are milled with long-chain fatty acids and diluted in weak alkaH solutions until dispersion occurs (81). Such latices usually have lower polymer concentrations after the solvent has been removed. For commercial uses the latex soHds are increased by techniques such as creaming. 

The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. The polymer is an excellent adhesive and possesses solvent-, oil-, and grease-resistant properties matched by few other polymers. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which, under dry conditions, are superior to those of any other known polymer. The polymer s low surface tension provides for excellent emulsification and protective coUoid properties. 

Leibler [17] and Noolandi et al. [18,19] developed thermodynamic theories concerning the emulsification of copolymers (A-b-B) in immiscible polymer blends (A-B). 

Microcapsules of PCL and its copolymers may be prepared by aircoating (fluidized bed), mechanical, and, most commonly, solution methods. Typically, the solution method has involved emulsification of the polymer and drug in a two-phase solvent-nonsolvent mixture (e.g., CH2Cl2/water) in the presence of a surfactant such as polyvinyl alcohol. Residual solvent is removed from the tnicrocapsules by evaporation or by extraction (70). Alternatively, the solvent combination can be miscible provided one of the solvents is high-boiling (e.g., mineral spirits) phase separation is then achieved by evaporation of the volatile solvent (71). The products of solution methods should more accurately be called microspheres, for they... 

As an example, a compact high-throughput turbulent flow reactor/mixer/heat exchanger was used for various applications, including polymer and rubber manufacture [50]. Further applications refer to emulsification and intensified heat exchange. 

An aqueous colloidal polymeric dispersion by definition is a two-phase system comprised of a disperse phase and a dispersion medium. The disperse phase consists of spherical polymer particles, usually with an average diameter of 200-300 nm. According to their method of preparation, aqueous colloidal polymer dispersions can be divided into two categories (true) latices and pseudolatices. True latices are prepared by controlled polymerization of emulsified monomer droplets in aqueous solutions, whereas pseudolatices are prepared starting from already polymerized macromolecules using different emulsification techniques. 

Direct emulsification A solution of the polymer within a volatile, water-immiscible organic solvent (or mixture of solvents), or a polymer melt is emulsified within a surfactant-containing aqueous phase. If used, the organic solvent is then removed by steam distillation to obtain the pseudolatices. 

Self-emulsification The polymer molecules are modified chemically by the introduction of basic (e.g., amino) or acidic (e.g., carboxyl) groups in such concentration and location that the polymer undergoes self-emulsification without surfactant after dispersion in an acidic or basic solution. 

The nanoemulsion mean droplet sizes were much smaller than those obtained in other systems using polar oil mixtures (above 500 nm) [18]. The findings verify that the low-energy emulsification methods are valid not only for aliphatic [9,10,13, 75, 76, 79-81] and semipolar oils [82-84], as reported in most studies devoted to low-energy emulsification, but also for polar solvent-preformed polymer mixtures. These nanoemulsions show good kinetic stability at 25 °C over a period of at least 24 h,... 

Latex or emulsion polymers are prepared by emulsification of monomers in water by adding a surfactant. A water-soluble initiator is added, e.g., persulfate or hydrogen peroxide (with a metallic ion as catalyst), that polymerises the monomer yielding polymer particles, which have diameters of about 0.1 pm. The higher the concentration of surfactant added, the smaller the polymer particles. 

This procedure is also referred to as the precipitation method and was first reported by Fessi et al. [105]. In this type of preparation, as shown in Figure 7, the polymer is dissolved in a water-miscible solvent and then poured under stirring into a nonsolvent, which is usually water. This leads to the polymer precipitating as nanospheres. Prior emulsification and inclusion of surfactants are not necessary. 

The number average diameter of microspheres obtained from polymers synthesized, by emulsification of polymer solutions followed by solvent extraction and/or solvent evaporation methods, can be controlled by choosing the appropriate conditions at which particles are produced. However, by this method particles with 15 p,m and with D D > 1.9 are produced. Spray drying did not provide poly(L-Lc) particles with regular spherical shape. Direct synthesis of poly(L-Lc) microspheres by ring-opening polymerization with stepwise monomer addition can be used as a method of choice for the production of microspheres with diameters controlled to ca. 6 p.m and with diameter polydispersity parameter < 1.20. 

M.J. Rang and C.A. Miller Emulsions and Microemulsions—Spontaneous Emulsification of Oil Drops Containing Surfactants and Medium-Chain Alcohols. Prog. Colloid Polym. Sci. 109, 101 (1998). 

Y. Sela, S. Magdassi, and N. Garti Newly Designed Polysiloxane-Graft-Poly (Oxyethylene) Copolymeric Surfactants Preparation, Surface Activity and Emulsification Properties. Colloid Polym. Sci. 272, 684 (1994). 

Recently, nonionic ortho ester surfactants have been used as emulsifiers for squalene, a polar oil [65]. In this case a polymer is used together with the surfactant. The emulsification is made under acidic conditions, and the surfactant breaks down rapidly after the emulsion is formed, leaving a surfactant-free, polymer stabilized emulsion with reasonable stability. 

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