A cast film

The thermal imidization of a polyamic acid film (PMDA-ODA or BPDA-ODA) obtained by casting an NMP solution leads to an amorphous polyimide. Two different teams have shown that a polyamic acid solutions in NMP heated at 200°C for a short time (20 min) gives polyimide particles fully cyclized and highly crystalline, as shown by X-ray diffraction and solid 13C NMR spectroscopy.151152 The chemical imidization of the same solution gives only amorphous particles. The difference between the cyclization of a solution and a casted film in the same solvent is intriguing. In the case of the solution, the temperature and the heating time are lower than in the case of the casted film as a consequence, a less organized structure would be expected for the particle. 

Another spectral change was found w hen a cast film of C AzoCgN+Br was annealed and then moistened (Figure 13). The type I spectrum of the as-cast film changed to the type V spectrum (the broken-line spectrum in Figure 13) after heating above its phase transition (115°C[22]), and then immediately shifted to the type III spectrum within 30 sec in a 75% humidity condition at room temperature. The type III state seemed to be another metastable state in the annealed film because the moisture induced isothermal transition from the type III to the type I required a long period (e.g. 13 hours even at 75% humidity). 

Running an LLDPE Resin on a Cast Film Process with Unmixed Gels in the Extrudate... 

Table 11.7 Screw Channel Dimensions for a 114.3 mm Diameter, 32 L/D Barrier Screw for Running an LLDPE Resin on a Cast Film Process with an Improved Screw Design...

Azole compounds, poly-N-vinylimidazole (PVI-1) and 2-undecylimidazole (UDI), are studied as alternative inhibitors to benzotriazole (BTA) for copper corrosion in aqueous systems using electrochemical techniques. It is shown that UDI, either as a cast film or dissolved in solution at concentrations as low as 7 X inhibits oxygen reduction on... 

Fig.1 Model for alignment of PAE No. 19 in Table 2 on the surface of a Pt plate. The powder XRD pattern indicates both and 2 peaks, whereas the XRD pattern of a cast film, measured with a reflection mode, gives only the di peak di= l.lS n+lO) A (n=number of carbon atoms in the OR group) [93,95]...

A cast film was obtained in which an island/sea structure exists and the islands were cross-linked. Then they were dispersed in a good solvent. 

An interesting experiment on a DNA-based network embedded in a cast film had already been done by Okahata et al. in 1998 [49]. In this pioneering experiment the DNA molecules were embedded (with side groups) in a polymer matrix that was stretched between electrodes (see Fig. 12). It was found that the conductivity parallel to the stretching direction (along the DNA) was 4.5 orders of magnitude larger than the perpendicular conductivity. 

THe network structure of these block polymers can also be altered by actually crosslinking the elastomeric polydiene chains, thus introducing a chemical network. In this approach it was necessary to use a crosslinking method which would not result in any measurable chain scission. Dicumyl peroxide (Dicup) was chosen for crosslinking an SIS polymer since this peroxide is known to accomplish exclusive crosslinking without any observable chain scission (3). The Dicup was dissolved in a THF solution of the polymer, and a cast film was prepared which was then vulcanized in a press at 155 °C for 35 min. A control sample, without Dicup was treated in the same way. 

Figure 14. Setting angle plotted against the lattice distortion parameter (40) ((O) melt crystallized (9) melt crystallized (l ) single crystal from p-xylene (A) cast film from tetrachloroethylene (" ,) pressure crystallized)...

Precipitation of the cast liquid polymer solution to form the anisotropic membrane can be achieved in several ways, as summarized in Table 3.1. Precipitation by immersion in a bath of water was the technique discovered by Loeb and Souri-rajan, but precipitation can also be caused by absorption of water from a humid atmosphere. A third method is to cast the film as a hot solution. As the cast film cools, a point is reached at which precipitation occurs to form a microporous structure this method is called thermal gelation. Finally, evaporation of one of the solvents in the casting solution can be used to cause precipitation. In this technique the casting solution consists of a polymer dissolved in a mixture of a volatile good solvent and a less volatile nonsolvent (typically water or alcohol). When a film of the solution is cast and allowed to evaporate, the volatile good solvent evaporates first, the film then becomes enriched in the nonvolatile nonsolvent, and finally precipitates. Many combinations of these processes have also been developed. For example, a cast film placed in a humid atmosphere can precipitate partly because of water vapor absorption but also because of evaporation of one of the more volatile components. 

Cast film extrusion. In a cast film extrusion process, a thin film is extruded through a slit onto a chilled, highly polished, turning roll where it is quenched from one side. The speed of the roller controls the draw ratio and final film thickness. The film is then sent to a second roller for cooling of the other side. Finally, the film passes through a system of rollers and is wound onto a roll. A typical film casting process is depicted in Figs. 3.53... 

For a successful production of a cast film, the dispersion has to wet the supporting surface and spread uniformly. In drying, the thickness of the deposited layer is very... 

A cast film of 28 also responded to the chirality of liquid and solid chiral amines, and exhibited an ICD in the UV-visible region. The observed Cotton effect patterns were similar to those of 28 induced by the chiral amines in solution [147]. These methods are more convenient and practically feasible to sense the chirality of chiral amines than the solution method, and may be applicable to other dynamic helical polyacetylenes. 

Figure 10.19 System diagram for direct extrusion of non-pre-dried PET to produce a cast film...

The process for making a cast film involves drawing a molten web of resin from a die onto a roll for controlled cooling. The cast film process is used to make a film with gloss and sparkle. The melt temperature in the cast film process is higher than in the blown film process. The higher the melt temperature the better are the optical properties of the film. 

The polyamide 6 (PA6) used was a cast film of 50 pm thickness made from an unstabilized PA6. The polybutylene terephthalate (PBT) used was a cast film of 25 pm thickness made of an unstabilized PBT. 

The layered structure of a cast film is controlled by the surface properties during evaporation. Significant compositional gradients can be generated by making use of the natural tendencies of one polymer to migrate toward the air-polymer Interface and the other toward the substrate. Hydrophobicity/hydrophilicity of macromolecules is often cited as the driving force (27, 28). 

Usually found as a cast film. It can readily be oriented and heat set. It can be produced in thin gauges (down to 12 Pm) as it is an extremely strong and tough material. Polyester is also clear and glossy. 

The temporal response of the third-order nonlinear optical susceptibility in poly(PTS) crystal was determined by time-resolved degenerate four-wave mixing (DFWM) by Carter and coworkers. The excited lifetime T ws measured to be 1.8 0.5 ps at 652 nm in the resonant region. The values of phase relxation time T2 measures by Hattori and Kobayashi for a cast film of poly(3BCMU) were 30 and 90 fs for the respective incident... 

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