Inhibited stretching film

Inhibited stretching film is used in stretch packages, a variant of which looks like (Fig. 2.55d) a blank of two cards (or sheet material) having a window reproducing the article shape. The article is covered from two sides by the stretching film whose ends are heat-sealed or bonded by some other method between two cards. 

Structural peculiarities of inhibited polymer films formed by extrusion encapsulation, i.e. stretching of films in a Cl followed by the thermal treatment, have been described elsewhere [4]. The capsules look like cylindrical voids in the polymer bulk filled by a liquid Cl and oriented along the stretching axis. 

Fig. 2.55. Combined packages of inhibited polymer films (a) skin pack (b) blister strip pack (c) blister bnbble pack (d) stretch package. (1) polymer film, (2) bottom card, (3) protected article...

This technique was employed to monitor the B —> A transition of DNA as a function of the relative humidity (Pilet and Brahms, 1973 Pohle et al., 1984). The investigated bands are those which reflect the vibrations of the phosphate groups. As shown by Fig. 4.7-3, which presents the polarized infrared spectra of a salmon sperm DNA hydrated film with 93% RH (top, B form) and 58% RH (bottom, A form), the dichroism of the two phosphate bands changes. The B form of the antisymmetric PO2 stretching vibration around 1230 cm is non-dichroic, while that of the A form is perpendicular. The B form of the symmetric PO2 stretching vibration around 1090 cm is perpendicular, while that of the A form is parallel. A simple computation, for instance for the latter band, shows that the value of the angle between the transition dipole moment of this vibration and the double helical axis varies between 68 ° (B form) and 49 ° (A form). This parameter is an extremely sensitive indicator of a B A transition and may also be employed to show the inhibition of a B —> A transition by various classes of molecules, such as proteins (Liquier et al., 1977 Taillandier et al., 1979) or drugs (Fritzsche and Rupprecht, 1990). 

A related study on the spectroelectrochemical behaviour of a copper electrode in [C4mim] [BF4] containing benzotriazole (BTAH) has been investigated by cyclic voltammetry and SERS [64]. A considerable decrease in the anodic currents in the presence of BTAH, as seen in the cyclic voltammograms, suggests that BTAH inhibits the oxidation of copper in the ionic liquid. The SERS results have shown that at potentials positive to the PZC for copper in the ionic liquid, a [Cu(I)(BTA)] polymeric film is formed as BTAH interacts with the copper(I). The polymeric film is responsible for the corrosion inhibition process. However, at potentials negative to the PZC, BTAH is found to adsorb chemically on the copper surface. This phenomenon is determined by the observation of the v(Cu—N) stretching mode and by the... 

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