Removing polymers

Many industrially important fluids cannot be described in simple terms. Viscoelastic fluids are prominent offenders. These fluids exhibit memory, flowing when subjected to a stress, but recovering part of their deformation when the stress is removed. Polymer melts and flour dough are typical examples. Both the shear stresses and the normal stresses depend on the history of the fluid. Even the simplest constitutive equations are complex, as exemplified by the Oldroyd expression for shear stress at low shear rates ... 

Sodium hydroxide, potassium hydroxide, or other caustic compounds are blended to make these types of removers. Polymer-type thickeners are added to increase the viscosity that allows the remover to be appHed with a bmsh, trowel, or spray. Some of these products use a paper or fabric covering to allow the remover finish mixture to be peeled away. The most common appHcation for this group of removers is the removal of architectural finishes from the interior and exterior of buildings. The long dwell time allows for many layers of finish to be removed with one thick appHcation of remover. 

Hydrofining has all the advantages of acid treating without the disadvantages. For example, acid treating does not readily remove refractory sulfur compounds such as thiophene the treated products must be rerun to remove polymers with a consequent yield loss and disposal of the acid sludges is a serious problem. 

Modem floor finishes contain mixtures of ingredients that when applied as a liquid dry to give a clear, durable film coating. Most floor finishes are combinations of polymers blended to provide unique and desirable characteristics such as durability, gloss retention, resistance to scuffing, fast-drying, and ease of removal. Polymers made up of more than one monomer or repeating unit are called copolymers. 

Fig. 9.1.8 Image of the coordination capture method to remove polymers from the metal nanoparticles surrounded by polymers.

The Anelli oxidation of alcohols to aldehydes and ketones has been accomplished using polymer-supported nitroxyl radical catalysts. The practicality of removing polymer-supported reagents by filtration to simplify product purification is highlighted by these examples. Bolm and coworkers11 demonstrated that a silica-supported nitroxyl catalyst is easily filtrated after use from the reaction solution, recovered and recycled, and the residual inorganic salts present in the reaction mixture are separated from the organic product by aqueous extraction (Table II, entry 7). 

From the oscillatory data, we can estimate the relaxation time of PFPEs as a measure of the time required for elastic recoil after stress removal. Polymer... 

Remove polymer vial and store in the dark at 4°C until ready to use. 

Remove polymer/DNA particles from the cells. Typically, particles are incubated on the cells for 1-4 h. Depending on the concentration and the toxicity of materials, in some case overnight incubations are helpful. After incubation, aspirate the polymer/DNA particles from each well using either a 6-channel aspirating wand or a Pasteur pipette. Add a volume of fresh, warm media equal to the initial cell seeding volume used in each well (i.e., 500 jxL for a 24-well plate). Return the cells to the incubator. 

Remove polymer/DNA particles from the cells. After a 1-4 h incubation time, aspirate the polymer/DNA solution from the cells and add 100 pL of warm fresh media to each well. Return the cells to the incubator. 

Since the functional end groups of the polymer molecules Pj formed are the same as those of the monomer M from which they were formed, one must expect monomer link-up per reactions 10.4 to be accompanied by link-up of polymer molecules with one another. Also, if the cast-off small molecule is not effectively removed, polymer molecules may split up again ... 

SC CO2 used as a carrier of drug molecules into a polymer matrix has a number of advantages such as the plasticizing ability of CO2 (based on specific interactions between CO2 and polymer moieties), which both enhances the diffusion rates of drug molecules into the polymer and facilitates solvent removal. Polymer plasticization is accompanied by the swelling of the polymer matrix, with a concomitant increase in the free volume of the polymer. Moreover, SC CO2 can reduce the melting temperature of semicrystalline polymers. These effects are crucial to the impregnation and modification of polymeric materials. 

SCF technology has spread quickly from molecules such as naphthalene to more complex substances such as polymers, biomolecules, and surfactants. Supercritical fluids can be used to reduce the lower critical solution temperature of polymer solutions in order to remove polymers from liquid solvents(6.26 The technology has been extended to induce crystallization of other substances besides polymers from liquids, and has been named gas recrystallization(4). In other important applications, SCF carbon dioxide has been used to accomplish challenging fractionations of poly(ethylene glycols) selectively based on molecular weight as discussed in this symposium, and of other polymers(. ... 

Adsorption refers to the interaction between polymer molecules and the solid surface. This interaction causes polymer molecules to be bound to the surface of the solid, mainly by physical adsorption, van der Waals forces, and hydrogen bonding. Essentially, the polymer occupies surface adsorption sites. Adsorption depends on the surface area exposed to the polymer solution, and it is the only mechanism that removes polymer from the bulk solution if a free solid powder, such as silica sand or latex beads, is introduced into the bulk solution and stirred until equilibrium is reached. 

Figure 6.7 shows that the elastic modulus and relaxation time of the polymer solution increased with polymer concentration, to was 1.351 radians per second. The HPAM 1275A and HPAM 1255 polymers were used. As polymer concentration increases, the distance between polymer molecules decreases. The entanglement of the long flexible chains will be more severe, and the van der Waals force will become larger so that it is more difficult for polymer molecules to deform. When the external force is removed, polymer molecules quickly return to their curling state. 

Laser Ablation of Kapton with 308-nm Irradiation. The laser ablation of Kapton at 308 nm has been studied previously in detail [276]. An ablation threshold of 40 mj cm-2 has been determined for the same Kapton samples and the same experimental setup as in this study. The term ablation threshold is defined in this study as the laser fluence necessary to remove polymer material in the irradiated area, measured by a profilometer. For this study we used laser fluences below, at, and above the threshold of ablation of Kapton films. 

Figure 3. The thinning curve, B, is obtained fix>m a series of contrast curves (development time increasing firom A to A "). The limiting value of normalized thickness is plotted versus the corresponding dose needed to remove polymer completely.

The monomeric building blocks are chemically bonded by a process known as polymerization that can take place by one of several methods. In condensation polymerization, the reaction between monomer units or chain endgroups release a small molecule, usually water. This is an equilibrium reaction that will halt unless the by-product is removed. Polymers produced by this process will degrade when exposed to water and high temperatures. 

The resulting models may be used in various applications, including chemical reaction equilibria, which is important to chemical reactor design, and phase equilibria, which arises in distillation, solvent extraction, and crystallization. But in addition to such traditional applications, thermodynamic models may also be used to help solve many other engineering problems, such as those involving surface and interfacial phenomena, supercritical extraction, hazardous waste removal, polymer and composite material development, and biological processing. 

I Calcination at 500°C to Superhydrophobicity remove polymer matrix (Contact angle >150°)... 

Calcination at 500°C to remove polymer matrix and hrge colloid... 

An approach that can be applied to laminates and coextrusions is to selectively dissolve and remove polymer layers by careful selection of solvents. Thus, the nylon layer in a polyethylene/nylon/polyethylene coextrusion can be isolated by boiling in xylene. Alternatively, the nylon could be removed by boiling in formic acid. Solvents for the selective removal of polymers are listed in Table 2. Acids or alkalis should be avoided on some polymers where there is a risk of reaction with the polymer. An example would be the use of concentrated sodium hydroxide solution on a metallized film comprising certain acrylic/ethylene... 

Mathiowitz, E., Amato, C., Dor, P., Langer, R 1990a. Polyanhydride microspheres 3. Morphology and characterization of systems made hy solvent removal. Polymer 31,... 

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