Polymer, solid phase dispersion

The above option could be especially advantageous for long-term storage of spent-removal units with cores previously filled with lead, radiation-resistant polymer, solid-phase dispersed material or silica sand. 

Al-Malaika, S. and Amir, E.J., Thermoplastic elastomers Part III—Ageing and mechanical properties of natural rubber-reclaimed rubber/polypropylene systems and their role as solid phase dispersants in polypropylene/polyethylene blends, Polym. Degrad. Stab., 26, 31, 1989. 

The in situ molecular imprinting protocol employing dispersion polymerisation has some advantageous features. The dispersion polymer can be removed from a column and re-packed when a column is damaged after repeated use. Back-pressure of agglomerated polymer particles is less problematic therefore, this in situ method can be applied to a wider range of analytical techniques. Here, two applications of in situ dispersion polymer, solid phase extraction (SPE) and CE are described. 

Matrix solid-phase dispersion (MSPD) was developed by researchers at Louisiana State University s School of Veterinary Medicine in order to isolate, identify, and quantify veterinary drug residues in livestock (Barker and Hawley, 1992). Compared to traditional methods, MSPD reduces solvent use by 98% and turnaround time by as much as 90%. The method involves the mechanical blending of a sample matrix with bulk C-18 sorbent. The C-18 hydrophobic phase has the ability to incorporate the lipids in meat and other food products into its matrix. Mechanical shearing forces initially disrupt the sample structure and disperse the sample over the surface of the C-18 bonded silica. The process causes the sample and polymer phase to become semidry, which then allow the material to be packed into a column (see Fig. 9.4). 

Several extraction techniques have been reported in the literature for the analysis of sulfonamides. Because of their polar nature, sulfonamides are readily extracted by organic solvents ° ° the most commonly used are acetonitrile.Other organic solvents used for analyte extraction and protein precipitation include dichloromethane, " acetone, ethanol, chloroform, and ethyl acetate, " which are often used either alone or in conjunction with one another. Other techniques used for protein precipitation include the use of acids such as perchloric or formic and the use of basic buffers such as potassium hydrogen phosphate and ammonium sulfate. In the case of honey, the use of acids such as trichloroacetic, " " hydrochloric, and phosphoric is necessary for hydrolysis, releasing carbohydrate-bound sulfonamide residues. Other extraction techniques reported in the literature include the use of pressurized liquid extractions, " matrix solid-phase dispersion, and magnetic molec-ularly imprinted polymers. Of additional note, several authors have observed that analyte recoveries were largely... 

Solid Phase Dispersion of Ultrafine Particles into a Polymer Through Thermal Relaxation... 

We have found quite a novel technique to make ultrafine metai particles-polymer composites The new technique consists of three steps. The first step is the preparation of the matrix polymer with a thermodynamicatly ntetastable structure.The second is the vacuum vapor deposition of the metal onto the matrix polymer. The last step is the heat-treatment of the polymer laminated with the thin rrtetal film. The metal disposes into the matrix polymer in the form of ultrafine particles through a series of treatments mentioned above. This dispersion process, named RAD Reiaxstive Auto-Oispersion), contains an intersting phenomenon of the solid phase dispersion. However, rto complete explanation has been offered about the actual dispersion mechanism yet. 

The reactor operates at a steady state with a polymer solids level above that at which phase inversion occurs and up to 70% polymer solids. Operation at such a polymer solids content ensures that upon addition the rubber immediately forms small particles containing a monomer component, dispersed in the partially polymerized reaction mixture. 

Quantitative PXRD and thermal analysis have been used to determine solid solubility of drugs in polymeric carrier [132-134], When phase separation occurs in solid dispersion, it results in formation of a drug-rich phase and a polymer-rich phase. The polymer-rich phase could retain, either by restricting molecular mobility or by interacting with drug, a certain portion of drug within its matrix. 

The portion of drug that remains trapped within the polymer may be estimated by measurfggf he the polymer-rich phase. In instances whl ef polymer-rich phase issimilartothatof neat polymer, a complete phase separation may be assumed. In other instances, the differ gsolid solubility of drug in polymer. As shown in Figure 18.12, phase separation of trehalose was observed from dextran solid dispersions in the 4-day and 34-day samples. However, a certain fraction of trehalose remained miscible with dextran as indicated by the substantially low... 

Emulsions and suspensions are colloidal dispersions of two or more immiscible phases in which one phase (disperse or internal phase) is dispersed as droplets or particles into another phase (continuous or dispersant phase). Therefore, various types of colloidal systems can be obtained. For example, oil/water and water /oil single emulsions can be prepared, as well as so-called multiple emulsions, which involve the preliminary emulsification of two phases (e.g., w/o or o/w), followed by secondary emulsification into a third phase leading to a three-phase mixture, such as w/o/w or o/w/o. Suspensions where a solid phase is dispersed into a liquid phase can also be obtained. In this case, solid particles can be (i) microspheres, for example, spherical particles composed of various natural and synthetic materials with diameters in the micrometer range solid lipid microspheres, albumin microspheres, polymer microspheres and (ii) capsules, for example, small, coated particles loaded with a solid, a liquid, a solid-liquid dispersion or solid-gas dispersion. Aerosols, where the internal phase is constituted by a solid or a liquid phase dispersed in air as a continuous phase, represent another type of colloidal system. 

Figure 1 Schematic cross-section of a drug delivery system. A circular slab, cut in half in the plane parallel to release, is shown in the background. The exposed internal face is blown up in the foreground, revealing discrete particles of solid molecule dispersed in a continuous polymer phase. 

The active material in our herbicide is a liquid that does not mix with water. It can be dispersed as droplets with a mixer - in our case the droplets have to be about 0.3 mm in diameter (Figure 11-7). If you then let a polymer-rich phase form by coacervation, the polymer spontaneously wets the drop surface. It forms a liquid polymer layer around the drop. Cross-linking the polymer gives a solid capsule. 

An impact modifier is a rubber phase dispersed in particulate form throughout the matrix of a polymer solid. Unlike plasticizers, the rubber particles retain their intrinsic properties as a separate phase. The glass transition temperature of the parent matrix is not lowered by the addition of an impact modifier. The rubber particles do two things to the parent matrix phase (2,3,4) they act as stress concentrators (i.e., a large strain will start in the matrix near the interface) and they enhance the multi-axiality in stress. As multiaxial tensile strength near the interface further enhances dilatation, which shortens the mechanical relaxation time, the otherwise brittle polymer solid of the matrix will undergo plastic deformation in the vicinities of the rubber particles. 

Spherical beads that can be expanded into foam under the influence of heat or steam are produced directly by suspension polymerization in the presence of blowing agent. The term suspension polymerization describes a process in which water-insoluble monomers are dispersed as liquid droplets with suspension stabilizer and vigorous stirring to produce polymer particles as a dispersed solid phase. Initiators used in suspension polymerization are oil-soluble. The polymerization takes place within the monomer droplets. The kinetic mechanism of the suspension process is considered to be a free radical, water-cooled microbulk polymerization [1]. 

Early work on production of stable polymer dispersions in hydrocarbon diluents is summarized in Ref. [ I ]. More reeently, publications in this field have been directed at polymerizations of nonpolar monomers in polar media, with the aim of producing large partieles with narrow size distributions for use such as toners and packings for solid phase peptide syntheses [2, 3]. 

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