Particle thickening polymer

In addition to the normal problems of completely dissolving particles of water-thickening polymers, xanthan gum contains insoluble residues which decrease polymer injectivity. Various methods of reducing insolubles content and improving xanthan solution injectivity are available (80—87). None appears economically viable. Oxygen scavengers (88) and bactericides (77,89) are commonly used to stabili2e injected polyacrylamide and xanthan gum solutions (90—102). 

Fluid loss additives such as solid particles and water-thickening polymers may be added to the drilling mud to reduce fluid loss from the well bore to the formation. Insoluble and partially soluble fluid loss additives include bentonite and other clays, starch from various sources, crushed walnut hulls, lignite treated with caustic or amines, resins of various types, gilsonite, benzoic acid flakes, and carefully sized particles of calcium borate, sodium borate, and mica. Soluble fluid loss additives include carboxymethyl cellulose (CMC), low molecular weight hydroxyethyl cellulose (HEC), carboxy-methYlhydroxyethyl cellulose (CMHEC), and sodium acrylate. A large number of water-soluble vinyl copolymers and terpolymers have been described as fluid loss additives for drilling and completion fluids in the patent literature. However, relatively few appear to be used in field operations. 

Suspensions of noninteracting rigid spheres are Newtonian up to volume fractions of ca. 25%.Interacting spheres, nonspherical particles, and polymer solutions frequently show non-Newtonian behavior at lower volume fractions, sometimes well below 5%. Most non-Newtonian behavior is shear-thinning, in that viscosity decreases with shear rate. The reverse effect, known as shear-thickening, is sometimes observed at higher shear rates in concentrated dispersions of relatively uniform particles. 

To obtain a suitable coating viscosity, and to prevent settling of filler particles, thickeners are often used. These are often low-cost natural products based on cellulose or casein. These are readily metabolized by many bacteria and fungi therefore, a biocide should be included. Biocides in powder form such as Captan (R.T. Vanderbilt) or Zinc Omadine (Akcros) can be dispersed with fillers and pigments. A useful starting point level is 1 percent by weight of the natural polymer to be protected. Alternatively, a biocide water dispersion, such as Nuocide 404-D (40.4%, International Specialty Products), can be used. 

Aqueous dispersions are alternatives to solutions of Hquid and soHd resins. They are usuaUy offered in 50% soHds and may contain thickeners and cosolvents as stabilizers and to promote coalescence. Both heat-reactive (resole) and nonheat-reactive (novolak) systems exist that contain unsubstituted or substituted phenols or mixtures. A related technology produces large, stable particles that can be isolated as discrete particles (44). In aqueous dispersion, the resin stmcture is designed to produce a hydrophobic polymer, which is stabilized in water by an interfacial agent. 

Figure 2.15 Equal volumes of a polymer-thickened dispersion. When the particles are aggregated there is a larger solvent volume available to the polymer molecules...

The grafted layer also affects two other features of the rheology. First, thicker polymer layers enhance the elasticity due to the longer range of the repulsion relative to the hard core size. Thus, samples formulated at 4>cff mo possess easily measurable static elastic moduli. Second, the softer repulsion apparently suppresses the shear thickening observed at high volume fractions for the harder particles, in accordance with earlier measurements by Willey and Macosko (1978). 

There are three chapters in this volume, two of which address the microscale. Ploehn and Russel address the Interactions Between Colloidal Particles and Soluble Polymers, which is motivated by advances in statistical mechanics and scaling theories, as well as by the importance of numerous polymeric flocculants, dispersants, surfactants, and thickeners. How do polymers thicken ketchup Adler, Nadim, and Brenner address Rheological Models of Suspensions, a closely related subject through fluid mechanics, statistical physics, and continuum theory. Their work is also inspired by industrial processes such as paint, pulp and paper, and concrete and by natural systems such as blood flow and the transportation of sediment in oceans and rivers. Why did doctors in the Middle Ages induce bleeding in their patients in order to thin their blood ... 

Here you find the pastes. Hazelnut paste is a dispersion of particles in a thick emulsion of two liquids, as is peanut butter. Jam is thickened by natural polymers. Soft cheese, butter and margarine are in the refrigerator these are complicated structures of fat crystals, oil, water and many other components. All these pastes have a yield stress that is low enough to let them be spread by a knife, but not so low that they run off bread. Users do find the cold butter a bit stiff and the jam a bit thin. As a developer you might want to improve these things. Bread - a solid foam - is a surprising structure when looked at it closely. Fresh bread is often too soft to cut easily. 

Several systems may be used such as polymeric thickeners, fine particulate solids such as bentonite clays and oxides or combinations of the latter with polymers (1). The nature and level of the gelling agent required to prevent appreciable settling of particles and formation of hard "cakes" or clays depends on the density difference between disperse phase and medium, volume fraction of the disperse phase and interaction of the antisettling system with particles of the pesticide. 

When an emulsifier is used, its type and concentration primarily affects the number of latex particles formed, which in turn determines the rate of polymerization and, depending also on the rate of initiation, the molecular weight of the polymer formed. Although the physical properties of the polymer are primarily dependent on its molecular waght and molecular weight distribution, the properties of the latex depend on its concentration, average particle size, particle size distribution, and the viscosity of the aqueous phase, which may be enhanced by addition of a thickener—a water-soluble polymer not adsorbed by the polymer phase which does not affect the course of the reaction,... 

The template-assisted synthetic strategies outlined above produce micro- or mesoporous stmetures in which amorphous or crystalline polymers can form around the organic template ligands (174). Another approach is the use of restricted spaces (eg, pores of membranes, cavities in zeolites, etc.) which direct the formation of functional nanomaterials within thek cavities, resulting in the production of ultrasmaU particles (or dots) and one-dimensional stmetures (or wkes) (178). For example, in the case of polypyrrole and poly(3-methylthiophene), a solution of monomer is separated from a ferric salt polymerization agent by a Nucleopore membrane (linear cylindrical pores with diameter as small as 30 nm) (179—181). Nascent polymer chains adsorb on the pore walls, yielding a thin polymer film which thickens with time to eventually yield a completely filled pore. De-encapsulation by dissolving the membrane in yields wkes wherein the polymer chains in the narrowest fibrils are preferentially oriented parallel to the cjlinder axes of the fibrils. 

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