Expandable polystyrene processing
First steps for simple foam or foam, set the density of the final product. Polymer particles contain foaming agents in this process in heated conditions soften, volatile blowing agent. Result in each bead expansion, creating many foam. Cell number (the final density) controlled by a temperature and heating time. This process, the bead must be decentralized and free-flowing State.
Industrial production, the foaming process expandable PS is placed directly in the steam, through beads and continuous mixing in a steam autoclave complete response, response equipment (like pre foaming machine) is to keep the outside pressure of atmospheric exposure and overflow the beads of foam from the top. Some time on production plant in order to ensure more balanced or when certain DPS requires a higher temperature using batch kettle. Foam beads after curing process, gradually mix the air in the cell.
The second step. First of all, the cured foam beads into the mold with a specific cavity. Products for small and complex structures, you want the venturi effect devices (such as fill gun). With air flow blown beads to the mold cavity. Large product under their own gravity is full of mold. Cavity enclosed and heated full of pellets, beads heat softened cell expansion. Bead foam expands to fill the space 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. Prior to the removal from the mold products, shall be such that the gas seeping pore diameter and lower temperature makes the product shape stability, this generally is the mould wall spraying method.