Cemre Ablay, 030060150, 12th Week

Dry Spinning:

In dry spinning, the starting polymer is in solution and the solvent can be separated by evaporation. The extrudate is pulled through a heated chamber that removes the solvent; otherwise the sequence is similar to the previous. Fibers of cellulose acetate and acrylic are produced by this process.

(Groover, M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, p.285)

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Wet Spinning:

In wet spinning, the polymer is also in solution-only the solvent is nonvolatile. To separate the polymer, the extrudate must be passed through a liquid chemical that coagulates or precipitates the polymer into coherent strands that are then collected onto bobbins. This method is used to produce rayon (regenerated cellulose fibers.)

(Groover, M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, p.285)

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Planar Coating:

Planar coating is used to coat fabrics, paper, cardboard, and metal foil; these items are major products for some plastics. The important polymers include polyethylene and polypropylene, with lesser applications for nylon, PVC, and polyester. In most cases, the coating is only 0.01 to 0.05 mm (0.0005-0.002 in) thick… In the roll method, the polymer coating material is squeezed against the substrate by means of opposing rolls. In the doctor blade method, a sharp knife edge controls the amount of polymer melt that is coated onto the substrate. In both cases, the coating material is supplied either by a slit-die extrusion process or by calendaring.

(Groover, M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, p.285-286)

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Sandwich Molding:

Sandwich molding involves injection of two separate polymers - one is the outer skin of the part and the other is the inner core, which is typically a polymer foam. A specially designed nozzle controls the flow sequence of the two polymers in the mold. The sequence is designed so that the core polymer is completely surrounded by the skin material inside the mold cavity. The final structure is similar to that of a structural foam molding. However, the molding possesses a smooth surface thus overcoming one of the major shortcomings of the previous process. In addition, it consists of two distinct plastics, each with its own characteristics suited to the application.

(Groover, M.P., Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, 4th Edition, p.294)