Processing methods sheet molding

Typical processing methods - compression molding, sheet extrusion, injection molding ... 

Typical processing methods bulk molding, casting, compression molding, encapsulation, injection molding, printed circuit board, pultrusion, resin transfer molding, sheet molding ... 

Ease of cure, easy removal of parts from mold surfaces, and wide availabiHty have made polyesters the first choice for many fiber-reinforced composite molders. Sheet mol ding compound, filament winding, hand lay-up, spray up, and pultmsion are all weU adapted to the use of polyesters. Choosing the best polyester resin and processing technique is often a challenge. The polyester must be a type that is weU adapted to the processing method and must have the final mechanical properties requked by the part appHcation. Table 1 Hsts the deskable properties for a number of fiber-reinforced composite fabrication methods. 

Figure 4.20. Elementary process flow sheets for molding an internal (a) and an external (b) anticorrosive coatings by the contmuous/subsequent filling method 1 - cylinder (shell) being coated, rotating on supports ...

With sheet molding, the procedures are very similar to those used as described above for billet molding except for the shape and size of the molding. This process is used for sheeting above 2.5 mm (0.1 in.) up to large blocks. The latter are used for a block method skiving operation similar to that used traditionally for cellulose nitrate. 

Film Processing Methods Through the use of conventional thermoplastic processing techniques, PCTFE can be molded as well as extruded into transparent film and sheet, " ] and laminated, heat-sealed, printed thermoformed, metallized, and sterilized... 

Different methods may be used to obtain the desired shape of the material. Sheets with thicknesses between about 0.5 and 2 mm may be produced by calendering. These may be densified further by pressing between two plates, which may be heated. Other possible processing methods include extrusion and injection molding or pressing. 

Vacuum molding n. This type of molding is used to mold fiberglass-reinforced plastics. The method allows molding without high temperatures and pressures. In this technique, layers of reinforced media are applied to the mold by hand. Resin is either sprayed or brushed on after each layer is positioned. The flexible sheet (usually cellophane or polyvinyl acetate) is placed over the lay up. Joints and seals are sealed and a vacuum causes the b to collapse over the face of the product not contacting the mold. The resultant pressure tends to eliminate voids and forces out any excess resin or entrapped air. Madox DM (1998) Handbook of physical vapor deposition (PVD) processing. Noyes Data Corporation, New York. 

Processing methods extrusion, injection molding, blow molding, thin-wall injection molding, injection stretch blow molding, sheet extrusion, blown fihn, cast film, rotomolding, and thermo-forming... 

J. Ferrarini, D. M. Longnecker, N. N. Shah, J. Feltzin, and G. G. Greth, Development of a Unique Method for the Preparation of High Quality SMC, 33rd Annual Technical Conference, R-P/C Institute, SPI, P. 1, Section 9-D (1978). ITP , interpenetrating thickening process. Sheet molding compounds based on SINs. Polyurethane/styrene-polyester. 

Thermoforming. The thermoforming process is applicable only to thermoplastic materials. In this process, a sheet of solid thermoplastic material, such as Plexiglas (polymethylmethacrylate) or polystyrene, is placed in a mold or form and heated to a temperature at which the material becomes highly pliable but does not melt. This allows the sheet to deform and adopt the shape of the mold, assisted by changing the pressure on one side of the sheet of material. The method is most suitable for designs that are relatively flat or low profile. 

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