Polymer removal

To a 50-mL three-necked flask (Fig. 3.18b) equipped with a stirrer (comprised of a stainless steel shaft and paddle), a head for the distillation of water, and a nitrogen inlet is added 20 g of purified 11-aminoundecanoic acid. The flask is then purged with nitrogen for 5 min. The flask is warmed in a silicon oil bath to 220° C and maintained at this temperature for 10 h. After raising the stirrer from the molten mass, the reaction is cooled under nitrogen and the resultant polymer removed by breaking the glass. The Tm of the polymer is 185—190° C and the rjmh in m-cresol (0.5% at 35°C) is 0.6—0.7. 

Prior to inclusion of PVP-protected Pt nanoparticles the SBA-15 silica is calcined at 823K for 12h to remove residual templating polymer. Removal of PVP is required for catalyst activation. Due to the decomposition profile of PVP (Figure 6), temperatures > 623 K were chosen for ex situ calcination of Pt/SBA-15 catalysts. Ex-situ refers to calcination of 300-500 mg of catalyst in a tube furnace in pure oxygen for 12-24 h at temperatures ranging from 623 to 723 K (particle size dependent) [13]. Catalysts were activated in He for 1 h and reduced at 673 K in H2 for 1 h. After removal, the particle size was determined by chemisorption. Table 2 is a summary of chemisorption data for Cl catalysts as well as nanoparticle encapsulation (NE) catalysts (see description of these samples in proceeding section). 

Table 38.2. Ninhydrin assays for surface amines on APS-SBA-15 materials, all materials were alkylated after polymer removal determined from elemental analysis frefluxed in 10% HCl in ethanol for 24 hours stirred with 25 wt%...

Isotactic poly(methyl methacrylate/methacrylic acid), a copolymer of methyl methacrylate and methacrylic acid, was synthesized by the partial hydrolysis of isotactic poly(MMA) according to the method of Klesper et al. (10-13). A hydrolyzing mixture of 8 mL dioxane and 4 mL methanolic KOH (10% by weight K0H) was mixed with 250 mg of polymer in closed vials at 85°C for 48 hr. Saponified polymer separated from the solution and adhered to the walls of the vial. The precipitated polymer was dissolved in water and then precipitated again with a few drops of HC1. The solution was warmed and the coagulated polymer removed, washed with water, and dried in vacuo at 50°C. The nmr spectrum indicated approxi-... 

Polymer Before Etching Ti Concentration Measured by XFS (atoms/cm2 x 10-15) After Etching (A/min.) Polymer Removal Rateb ATi Upon Etching (%)... 

A number of different methods can be used to prepare polymer film-coated electrodes. The simplest is to dip the surface to be coated into a solution of the polymer, remove the electrode from the solution, and allow the solvent to evaporate. While this method is simple, it is difficult to control the amount of material that ends up on the electrode surface. Alternatively, a measured volume of solution can be applied to the surface to be coated. This allows for accurate control of the amount of polymer applied. The polymer film may also be spin-coated onto the electrode surface. Spin-coating is used extensively in the semiconductor industry and yields very uniform film thicknesses. 

Commercially available static mixer reactors (SMR) as large as 1.8 m in diameter are operating in the production of nylon, silicones, polystyrene, polypropylene, and other polymers. Removing heat from a highly exothermic reaction in a static mixer equipped with a simple cooling jacket is limited by heat transfer to small diameters, typically less than 6 in. A new type of static mixer has been developed to overcome laminar heat-flow transfer problems. It is called the SMR mixer-heater exchanger-reactor (Mutsakis et al, 1986). 

Research on model compounds and sharp oligomer fractions has already had a profound effect on our understanding of polymer crystallization and morphology. The availability of monodisperse polymers removes the dependence of this field of science on essentially impure multicomponent experimental systems. It also helps close the gap between polymer science and mainstream chemistry and physics. 

In all reactions, the conversion of the starting aryl halide is high and the amount of organotin by-product is very low. At the end of the catalytic run, the amount of Sn is up to 16 ppm in the crude reaction mixture with the insoluble polymer removed, and it is less than 1 ppm in the product purified by chromatography on silica gel. ... 

In most cases, polymer adsorption is considered irreversible that is, it does not decrease as polymer concentration decreases (Szabo, 1979 Lakatos et al., 1979 Gramain and Myard, 1981). The irreversible effect is caused by polymer adsorption on rock. However, this is not exactly true because small amounts of polymer can be removed from porous rock using prolonged exposure to water or brine injection. Usually, however, the rate of release is so small that it is not possible to measure the concentrations accurately. It is thus more accurate to state that the rate of polymer retention is much greater than the rate of polymer removal. Retention also may occur when flow rates are suddenly increased. This process is called hydrodynamic retention, which is reversible (Green and Willhite, 1998). 

Cumulative amount of polymer removed from the columns. ... 

Cumulative amount of polymer removed from the columns. 8% D4. Table 9.20 Reaction/Extraction Results with Poly(dimethyl) -c<9-(diphenyl)siloxane ... 

Devolatilization. Following polymerization of many polymers, removal of residual monomer or solvents is necessary. Ultimately this removal becomes controlled by diffusion from the polymer no matter what type of process is employed (27). Many processes use a steam-stripping operation for this purpose, and others employ devolatilization in a vented extruder. Removal of residual vinyl chloride monomer from poly(vinyl chloride) was an issue of much concern following the discovery that this monomer is a carcinogen. 

Fig. 44. Etch rate of polysilicon, oxide, and photoresist as a function of hydrogen addition to a CF4 discharge. Etch rate stops on non-oxide materials due to polymer build up at high % H - Oxide continues to etch due to polymer removal by the available oxygen. This yields high selectivity of etching oxide over silicon. After [220].

To an open autoclave is added A/-vinylcarbazole which is then melted at 65 C. Then 0.02% di-te/ f-butyl peroxide and 0.01% azobisisobutyronitrile is added with stirring. The vessel is sealed, pured with nitrogen, and pressured to 40 atm with nitrogen. The autoclave is heated to 80°-90°C to initiate polymerization as evidenced by a rapid increase in temperature. After the maximiun temperature has been reached the polymerization reaction mixture is cooled under pressure. The autoclave is vented and the glassy polymer removed. 

The large-scale manufacture of addition polymers is usually via a continuous process, with monomer addition and polymer removal occurring at a... 

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