Casting polymer

DADC HomopolymeriZation. Bulk polymerization of CR-39 monomer gives clear, colorless, abrasion-resistant polymer castings that offer advantages over glass and acryHc plastics in optical appHcations. Free-radical initiators are required for thermal or photochemical polymerization. 

Solvent evaporation A mixture of solvents is used to form the polymer casting solution. Evaporation of one of the solvents after casting changes the solution composition and causes precipitation... 

Figure 3.12 Membrane formation in water-precipitation membranes was first rationalized as a path through the three-component phase diagram from the initial polymer casting solution (A) to the final membrane (D) [24]...

It was proposed that the temperature dependence of polymer 5 arises from the temperature dependence of the kA step. Specifically, it was suggested that the polymer segments to which the radicals are attached are conformationally stressed. There are two possible modes for the newly formed radicals to relax and become separated They can rotate or recoil away from each other (Scheme 9). These secondary motions of the polymer arise from the relaxation of unfavorable bond conformations that are formed during the polymer casting process. The increased thermal energy facilitates the rotation and recoil relaxation processes, which effectively increases the rate constant for diffusion of the radicals out of the cage, kA. This leads to decreased radical-radical recombination and consequently an increase in photodegradation efficiency. 

Pt electrodes for CE high voltage were embedded into PDMS pre-polymer cast against a mold. Upon curing, the Pt electrodes were well positioned at the solution reservoirs of the PDMS chip [292]. Metal electrodes were pierced through the PDMS well when the chip was mounted [293]. 

Upon doping with iodine vapor. Determined on thin films of polymers cast on glass substrate by the use of the four-probe technique. 

The organic thin films used in lithography are polymer casting films, Langmuir-Blodgett (LB) films, SAMs and plasma-polymerized films. The molecular designs and syntheses of organic monolayer materials are studied for SPNL resists [89]. 

This leads to typical values at room temperature of 5xlO-6m2V-1sec-1 for films of soluble PPV polymers cast from solution. At 30 K a value of 3 x 10-4 m2V-lsec-1 was obtained for poly(2,3-dibutoxy-l,4-phenylenevinylene). Comparison with ESR data shows that in PAni the intra-chain motion of negative and positive polarons is similar but that negative polarons are more mobile between chains. j... 

Two different techniques have been employed for the precipitation of membranes from a polymer casting solution. In the first method, the precipitant is introduced from the vapor phase. In this case the precipitation is slow, and a more or less homogeneous structure is obtained without a dense skin on the top or bottom side of the polymer film. This structure can be understood when the concentration profiles of the polymer, the precipitant and the solvent during the precipitation process are considered. The significant feature in the vapor-phase precipitation process is the fact that the rate-limiting step for precipitant transport into the cast polymer solution is the slow diffusion in the vapor phase adjacent to the film surface. This leads to uniform and flat concentration profiles in the film. The concentration profiles of the precipitant at various times in the polymer film are shown schematically in Figure 13. 

The first prototype micromixer was a roughly 1 mm thick silicon plate with the dimensions of ca. 17 X 30 mm (Fig. 15.4). The hrst trivial task to be solved was how to introduce reagents and organic solvents into this micromixer. The first approach was to glue a hypodermic needle onto the silicon chip. The resulting construction was fairly fragile and had to be stabilized by a polymer cast. 

These polyurethanes (and their precursors or analogues) were cast from an appropriate solvent, usually DMF, onto the glass bead surfaces used in the in vitro test for platelet retention (4), or for the thrombin absorption test used previously (2). Crystals of KBr for Fourier transform infrared (FTIR) spectroscopy and glass microscopic slides for examination by XPS (ESCA) served as supports for polymers cast from the same solvents. Concentration of polymer (5 wt %), temperature of casting... 

Polymers of approximately 400-500 poises are used most frequently in sealants and adhesives, while the lower viscosity polymers are most frequently used for flexibilizing epoxy polymer casting compounds. 

Effect of Fillers on Cured Compositions Based on LP -32 Polymer (Cast Sheets Cured 7 Days at 70-72°F (21-22°C) and 44-48% RH)... 

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