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A major polycarbonate market is the production of compact discs, DVDs, and Blu-ray discs. [13] These discs are produced by injection-molding polycarbonate into a mold cavity that has on one side a metal stamper containing a negative image of the disc data, while the other mold side is a mirrored surface.
A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations.
Co-kneaders and twin screws (co- and counter rotating) as well internal mixers are the most common used compounders in the plastic industry. [3] The extrudate, which look like long plastic strands, are then cooled in a water bath, or by spraying as the conveyor belt moves it to the granulator. The granulator breaks the strands into the desired ...
Besides plastics production, plastics engineering is an important part of the industrial sector. The latter field is dominated by engineering plastic as raw material because of its better mechanical and thermal properties than the more widely used commodity plastics .
This process is the same as a regular extrusion process up until the die. There are three main types of dies used in this process: annular (or crosshead), spider, and spiral. Annular dies are the simplest, and rely on the polymer melt channeling around the entire cross section of the die before exiting the die; this can result in uneven flow.
The blow molding process begins with softening plastic by heating a preform or parison. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can enter. The plastic workpiece is then clamped into a mold and air is blown into it. The air pressure inflates the plastic which conforms to the mold.
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The above mechanism considered crystallization from the melt, which is important for injection molding of plastic components. Another type of crystallization occurs upon extrusion used in making fibers and films. In this process, the polymer is forced through, e.g., a nozzle that creates tensile stress which partially aligns its molecules. Such ...