Contents 10 Emulsions

The high BCO content emulsions had very high viscosity which would make them difficult to use in most applications. 

This paper reports results on one phase of a program of study of concentrated oil-in-water emulsions, namely the effect of several composition variables on the apparent viscosity of concentrated (60 volume percent) crude oil-in-water emulsions. In particular, the effects of NaOH content, NaCl content, emulsion preparation technique, crude oil viscosity and aging of emulsion were studied. 

Generally speaking, the viscosity of the moderate to high NaOH content emulsions without salt increased slightly the first two to six days and then decreased (see Fig. 7). For the. emulsions made with low NaOH content, the viscosity of the lower layer increased but separation was so great that the aging results are not reliable. For the emulsions with salt, the increase of viscosity was continuous for the ten days as shown in Fig. 7. 

Although attempts to incorporate sulfur in asphalt were initiated many years ago (1, 2) and different authors investigated the sulfur/ asphalt system (3, 4, 5, 6), the SNPA process produces very fine particles because of specific dispersion conditions. This important dispersion results in a stable high sulfur-content emulsion which has specific viscoelastic properties in a very large temperature range (especially low temperatures). 

The use of block copolymer surfactants was already quite popular [1] for stabilization of both emulsion and dispersion polymers, but usually these products were nonionic (noncharged). A renewable interest now seems to be paid to block copolymer carrying charges for stabilizing high-solid-content emulsion polymer [138]. This topic was reviewed by Guyot and Tauer [139]. 

The dispersion form of PTFE consists of a fairly high solids content emulsion of PTFE in water. These products are produced by the same polymerization process as fine powder PTFE. Dispersion recovered firom the polymerization reactor is usually concentrated to raise the PTFE content. Additional surfactants may be added to prevent coagulation of small particles. 

Figure 7 Micrographs and linear viscoelastic properties of PMMA/Rubber blends for various values of rubber content emulsion model s predictions.

For instance, the home preparation of mayonnaise, a high internal phase content emulsion, consists of adding drops of oil to egg yolk, which is the water phase with a hydrophilic smfactant. The corresponding change follows the horizontal bold arrow located in the lower part of zone A in Fig. 4, left graph. It is worth noting that adding a teaspoon of mustard to the egg yolk... 

The standard NF T 65-011 distinguishes the bitumen emulsions by their ionic nature (anionic or cationic), their stability with respect to agglomerates and weight content of base binder. There are 20 grades of emulsions. 

Increasingly, dielectric measurements are being used to characterize the water content of emulsions. One model for the dielectric constant of a suspension, ... 

Before polyacrylamides are sold, the amount of residual acrylamide is determined. In one method, the monomer is extracted from the polymer and the acrylamide content is determined by hplc (153). A second method is based on analysis by cationic exchange chromatography (154). For dry products the particle si2e distribution can be quickly determined by use of a shaker and a series of test sieves. Batches with small particles can present a dust ha2ard. The percentage of insoluble material is determined in both dry and emulsion products. 

The ABS polymer is recovered through coagulation of the ABS latex. Coagulation is usually achieved by the addition of an agent to the latex which destabilizes the emulsion. The resulting slurry can then be filtered or centrifuged to recover the ABS resin. The wet resin is dried to a low moisture content. A variety of dryers can be used for ABS, including tray, fluid bed, and rotary kiln type dryers. 

M ass Process. In the mass (or bulk) (83) ABS process the polymerization is conducted in a monomer medium rather than in water. This process usually consists of a series of two or more continuous reactors. The mbber used in this process is most commonly a solution-polymerized linear polybutadiene (or copolymer containing sytrene), although some mass processes utilize emulsion-polymerized ABS with a high mbber content for the mbber component (84). If a linear mbber is used, a solution of the mbber in the monomers is prepared for feeding to the reactor system. If emulsion ABS is used as the source of mbber, a dispersion of the ABS in the monomers is usually prepared after the water has been removed from the ABS latex. 

The incidence of these defects is best determined by high resolution F nmr (111,112) infrared (113) and laser mass spectrometry (114) are alternative methods. Typical commercial polymers show 3—6 mol % defect content. Polymerization methods have a particularly strong effect on the sequence of these defects. In contrast to suspension polymerized PVDF, emulsion polymerized PVDF forms a higher fraction of head-to-head defects that are not followed by tail-to-tail addition (115,116). Crystallinity and other properties of PVDF or copolymers of VDF are influenced by these defect stmctures (117). 

In another extractor (Automatic Machinery and Electronics Inc. (AMC)) the individual fmits are cut in half as they pass a stationary knife. The halves are oriented in a vertical plane, picked up by synthetic mbber cups, and positioned across plastic serrated reamers revolving in a synchronized carrier in a vertical plane. As the fmit halves progress around the extractor turntable, the rotating reamers exert increasing pressure and express the juice. The oil and pulp contents in the juice increase with greater reaming pressure. The recoverable oil is removed in a separate step prior to juice extraction. Needle-sharp spikes prick the peel of the whole fmit, releasing oil that is washed away with water and recovered from the oil—water emulsion. 

The fluid is formulated from a premium mineral od-base stock that is blended with the required additive to provide antiwear, mst and corrosion resistance, oxidation stabdity, and resistance to bacteria or fungus. The formulated base stock is then emulsified with ca 40% water by volume to the desired viscosity. Unlike od-in-water emulsions the viscosity of this type of fluid is dependent on both the water content, the viscosity of the od, and the type of emulsifier utilized. If the water content of the invert emulsion decreases as a result of evaporation, the viscosity decreases likewise, an increase in water content causes an increase in the apparent viscosity of the invert emulsion at water contents near 50% by volume the fluid may become a viscous gel. A hydrauHc system using a water-in-od emulsion should be kept above the freezing point of water if the water phase does not contain an antifreeze. Even if freezing does not occur at low temperatures, the emulsion may thicken, or break apart with subsequent dysfunction of the hydrauHc system. 

The higher, long-chain dimers as weH as the tetramer dehydroacetic acid are far more stable and can be handled safely. The alkylketene dimers (AKDs) are shipped to the paper industry in tank tmcks in the form of ready-to-use aqueous emulsions with a total soHds content of 12—25% and a guaranteed shelf life of 30 days, as they have good hydrolytic stabHity. In this form they are not combustible Hquids, and are Hsted in the Canadian Domestic Substances List. 

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