Colloid solid, mechanical properties

The chemical treatment methods reduce dispersability property, of drilling fluids through the increase of size of cuttings which improves separation and prevents the buildup of colloidal solids in the mud. These methods include ionic inhibition, cuttings encapsulation, oil phase inhibition (with oil-base muds), and flocculation. The mechanical solids removal methods are based on the principles presented in Table 4-55. 

The key to the successful application of high performance, pourable nitrocellulose plastisols lies in a reasonably priced, high quality source of fine-particle, at least partially colloided, spheroidal nitrocellulose. Here we are speaking of particles much finer than the well-known ball powder, produced by the Olin Mathieson Chemical Co. for small arms for over 30 years (7). Actually, particles on the order of 5-50/x diameter appear to be required to assure a reasonable continuum of uniformly plasticized nitrocellulose binder in a propellant containing 45% or more of combined crystalline oxidizer and powdered metal fuel. Such a continuum of binder is necessary to assure acceptable mechanical properties and reproducible burning characteristics of the finished propellant. Preincorporation of a certain content of the water-insoluble solids within the nitrocellulose microspheres is an effective means of helping to assure this continuum of binder and alleviates the requirements for extremely small ball size. The use of a total of 45% or more of crystalline oxidizer and (generally) metal fuel is essential if the propellant is to be competitive with other modern propellants now in service. 

Bodmeier, R. Paeratakul, O. Mechanical properties of dry and wet cellulosic and acrylic films prepared from aqueous colloidal polymer dispersions used in the coating of solid dosage forms. Pharm. Res. 1994, 11 (6), 882-888. 

The results of experiments with different colloids demonstrate some of the ways in which macromolecules of various sizes, shapes, and surface properties may interact to form, in some cases, ordered solutions similar to liquid crystals and, in other cases, three-dimensional networks with the properties of a solid and how the order or the structure present determines the mechanical properties. 

Bayer RK (1994) Structure transfer from a polymeric melt to the solid state. Part III influence of knots on structure and mechanical properties of semicrystalline polymers. Colloid Polym... 

Gels are three-dimensional networks made up of molecules, polymers, particles, colloids, etc., that are connected with each other by the specific parts on them such as functional groups and associative groups. The connected parts are called cross-links. Gels usually contain many solvent molecules inside their networks, and hence they are close to liquid in composition, but show solid-like mechanical properties due to the existence of the cross-links [1 ]. 

The vehicle format we have used to produce aquasomes is the complex particulate multicomponent system. In general, complex particulate delivery systems are assemblies of simple polymers, complex lipid mixtures or ceramic materials that tend to measure individually between 30 and 500 nm in diameter. Being solid or glassy particles dispersed in an aqueous environment, they exhibit the physical properties of colloids their mechanism of action is controlled by their surface chemistry. They may deliver agents through a combination of specific targeting, molecular shielding, and slow release processes. 

Emulsions are metastable colloids made out of two immiscible fluids, one being dispersed in the other, in the presence of surface active agents. The droplet volume fiaction may vary from zero to almost one dense emulsions are sometimes called biliquid foams since their structure is very similar to the cellular structure of air-liquid foams for which the continuous phase is very minor. From dilute to highly concentrated, emulsions exhibit very different internal dynamics and mechanical properties. When diluted, droplets are agitated by Brownian motion and behave as viscous Newtonian fluids, whereas when more concentrated, namely above the random close packing volume fraction which is 64% for monodisperse droplets, the internal dynamics are severely restricted and they behave as viscoelastic solids. Simple direct emulsions are composed of oil droplets dispersed in water while inverse emulsions are composed of water droplets dispersed in an oil continuous phase. In fact, emulsions are in principle made out of two immiscible phases for which the interfacial tension is therefore non-zero, and may involve other hydrophilic-like or lipophilic-like fluids in the presence of suitable surface active species, each phase being possibly comprised of numerous components. Sometimes, simple emulsions may also contain smaller droplets of the continuous phase dispersed within each droplet of the dispersed phase. Such systems are called double emulsions or multiple emulsions. ... 

It will be clear from the previous section how much the study of the rheological properties is connected with the structure of colloid systems and how this conversely furnishes data on that structure in so far as the latter is not known a priori. The samc thing holds in the solid systems for the mechanical properties there also the consequences of applied deformation are governed by the structure of the system ... 

The statistical mechanical approach, density functional theory, allows description of the solid-liquid interface based on knowledge of the liquid properties [60, 61], This approach has been applied to the solid-liquid interface for hard spheres where experimental data on colloidal suspensions and theory [62] both indicate 0.6 this... 

---