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The Whole Processing of EPS(Expandable Polystyrene)

Author: Date:2010-11-30 10:15:51
Expandable Polystyrene, EPS for short, is manufactured by combining styrene with isobutylene under pressure. When manufacturing EPS products, tiny beads of poly styrene are expanded and consolidated in the process of steam heating and pressure treatment. When heated, the expanding agent enlarges the beads as much as 50 times, after which they are fused by pressure into huge blocks of EPS. These blocks are cured, then cut and shaped to produce a variety of EPS products, bringing lots of benefits to the construction and packing industries.
Pre-Expansion and Aging
The raw material resin used to manufacture EPS is received in the form of small beads ranging from 0.5 to 1.3mm in diameter. These small beads are formulated and manufactured by the suppliers to contain a small percentage of the naturally occurring gas pentane. This gas is impregnated throughout the body of each small bead. The pre-expansion phase of manufacturing is simply the swelling of the small bead to almost 50 times its original size through the heating and rapid release of the gas from the bead during its transition phase.
Molding of Blocks
The molding process involves taking the loose expanded beads and forming them into a solid block mass. Blocks are formed using a vacuum assisted, block mold. By utilizing a system of load cells, a computer is capable of controlling the exact weight of beads introduced into the mold cavity. Once the cavity is filled, the computer uses a vacuum system to evacuate residual air from the cavity. The vacuum is relieved by live steam which flows over the entire mass of beads in the cavity. This vacuum rinsing process softens the polymer structure of the bead surface and is immediately followed by the pressurization of the mold cavity with more live steam. The latent heat from the steam and subsequent pressure increase cause the beads to further expand. Since the block mold is a confined environment, the only way the beads can expand is to fill up any voids between them causing the soft surfaces to fuse together into a polyhedral type solid structure. The computer releases the pressure after it reaches its predetermined set point. The loose beads are now fused into a solid EPS block.
Heat curing is the next step of the process. This not only accelerates the curing process of the freshly molded blocks, but also assures that the material is dimensionally stable and provides a completely dry material for best fabrication results.

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