Liquid-filled inhibiting film

Fig. 2.9. Extrusion head for manufacture of liquid-filled inhibiting film (see explanations in the text)...

Fig. 2.3. Structure of inhibited polymer films (a) single-layered filled with solid Cl particles (b) with a layer of glued particles (c) with a porous layer impregnated with inhibited liquid (d) with a liquid Cl in the glued layer (e) with a liquid Cl between film layers (f) with Cl in the gaseous phase sealed between layers (g) with a layer foamed by an inhibited gas. (1) polymer base (2) Cl particles (3) porous layer (4) glued inhibited layer (5) gaseous pellet of Cl vapors (6) jelly layer with inhibited liquid...

The simplest modifications of named materials are multilayered and combined films in which either solid [41] or porous polymer layers (foamed, fibrous, etc.) are filled with the inhibiting liquid [4,18,23,24,30,39]. In addition, film materials where the adhesive layer is filled by a liquid Cl are used in packaging techniques [4,23,37]. 

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. 

The structural capsules start to be formed in films subjected to deformation in liquids until some tension threshold. Microcracks and microvoids appear and are filled with the inhibiting liquid under tensile stresses exceeding the polymer flow limit. Capillary channels connecting these voids with the process liquid and with each other start to merge or open in the course of structural transformations but do not disappear fully. The liquid may move over the network of the formed channels beyond the polymer matrix limits or concentrate in some voids able under certain conditions to enlarge the manifold. Thermal treatment of the deformed film intensifies the relaxation processes in the polymer matrix, the film shrinks in the tension direction and the capillaries between voids link up densely, thus insulating liquid particles from each other. If the film is treated in the extended state, a more complex mechanism of microcapsule formation is realized [4]. Cl liberation from microcapsules is related to their ability to break spontaneously under residual... 

It is thus possible to calculate the time needed to attain a given exudation value. In Figs. 2.30a and b one can see the lines of equal time values required for isolation of 2 wt% of the inhibiting liquid. The isolation rate at the initial stage of exudation is seen to have a strong dependence on the film-filling degree of the Cl. It is also a parameter that is sensitive to variations in the PhCI ratio, which is specifically evident at their low thermodynamic compatibility (Fig. 2.30b). 

---