Expandable Polystyrene EPS processing can be divided into two steps. First steps for simple foam or foaming, set the density of the final product. Vesicant polymer particles in so doing softens under heating conditions, blowing agents volatilize. The result is generated within each bead expansion, creating many foams. The number of cell (final density) controlled by heating temperature and heating time. This process, the bead must be decentralized and free flowing. Industrial production, the procedure is an Expandable Polystyrene EPS foam is placed directly on steam, generally through the beads and steam in a continuous mixing in stirred tank complete reaction, response equipment (like Rodman pre foaming machine) is to keep the outside pressure of atmospheric exposure and overflow the foam beads from the top. Some production plants in order to make the stay more balanced or when some of the EPS need to compare at high temperature using batch kettle. After foam beads through a process of maturation, allowing air gradually introduced into the cell in it.
The second step of Expandable Polystyrene EPS is thermoforming. First of all, the cured foam beads into a stencil with a specific cavity. Products for small and complex structure, when venturi effect devices to be used (such as fill gun), with air flow will bead into the mold cavity. Large product according to its gravity is full of mold. Pellet-filled cavity sealing and heat beads heat softened, cause the cell to swell. Bead foam expands to fill the spaces between each other and bonding into a smooth foam. At this point the foam remains soft cell heat and under the pressure of the gas. Before you remove the product from the mold, gas leakage shall be made porous and lowers the temperature so that shapes stable, which is generally used to die of inner wall of water spray method.
Because the mould is double-walled, PS foam molding is called a "steam room". Size is actual product size of mould wall, mold stomata on the inner wall, so that the steam through the foam and the heat spread out. Double wall space between the steam Chamber, into which steam for heating beads. For most products, Expandable Polystyrene EPS foam molding pressure below 276kPa. Die cast aluminum products and request a certain shape. PS foam molding due to the low pressure, low cost of molding equipment and is therefore a cost-effective production methods.