Sheet/film formation

When finest grain stmcture and maximum image sharpness are required, the original is photographed in a large-format camera using a separate sheet of film for each exposure. These cameras are heavier than roll-film cameras and usually require a tripod and/or a controlled studio environment. Common sheet film sizes include 102 x 127 mm (4x5 in.) and 203 x 254 mm (8 x 10 in.). 

One-Step Cameras and Processors. The eadiest one-step cameras used roU film and completed processing inside a dark chamber within the camera (9). The first instant color film, Polacolor, was provided in roU film format to fit these cameras. Flat-pack film cameras (Fig. 2), introduced in 1963, permitted the film to be drawn between processing rollers and out of the camera before processing was completed (10). Film holders for instant 10 X 13 cm (4x5 in.) film packets contain retractable rollers that permit the film to be loaded without mpturing the pod (11). For 20 x 25 cm (8 x 10 in.) films, the processing rollers are part of a tabletop processor. The exposed film, contained in a protective black envelope, and a positive sheet with pod attached are inserted into separate slots of a tray that leads into the processor. The film passes through the rollers into a covered compartment within which processing is completed. 

Die forming (including sheet and film formation, tube and pipe formation, fiber formation, coating, and extrusion)... 

Pyrocat-HD is a Pyrocatechin/Phenidone-based developer formula that can be used for development in tanks or trays. It is also recommended for JOBO and other rotary type processing in tubes and drums. Although originally meant for sheet film, subsequent use has shown that it is also an excellent developer for use with 35 mm and medium-format films because of its high acutance and tight grain pattern. 

To explain the fact that HSPAN swells in water to form gel sheets or macroparticles rather than disintegrating into a gel dispersion, we initially felt that chemical bonding must take place between individual particles of water-swollen gel as water evaporates. Although we cannot totally eliminate this possibility, the proposal of primary chemical bonding is not necessary to explain the behavior of these films and conglomerates. For example, Voyutskii (19) has reviewed the formation of films from vulcanized rubber latexes and concludes that film formation in these systems is observed because of interdiffusion of ends of individual macromolecules in adjacent latex particles. This diffusion can take place even though individual latex particles are crosslinked, 3-dimensional networks and the continuity of the resulting films, even when... 

Pigments Dyes Co-solvents (5-50%) Prevent nozzles from drying out Retain paper sheet flatness after printing Enhance ink film formation... 

Films and sheets of various fluoropol5miers can be produced by different film formation techniques. Processing methods are described for some of these films. 

Thermoplastic fusible adhesives (see Hot melt adhesives) may be used in the production of adhesive-bonded non-wovens, as powders, fibres or sheet films. The formation of strong bonds between the fibres occurs as the softened thermoplastic adhesive material resolidifies on cooling. The amount of adhesive incorporated in the web governs the strength of the fabric. 

Film formation Term applied to an extruded sheet of a polymer. 

---