Directly adding low boiling point liquid to extrusion foaming method
DATE：2021/12/6 9:26:30 / READ： / SOURCE：This station
Directly adding low boiling point liquid to extrusion foaming method
Directly add low-boiling point liquid foaming method to use emulsion polymerization of polystyrene, use polyethylene powder resin as raw material, mix with foaming agent, heat and press to fuse the mixture into hair, and then heat and foam to make foam plastic . Compared with expandable polystyrene foam, this kind of foam has high mechanical strength, uniform cells, no bead fusion interface, the entire foam is uniform, and has good dielectric properties. 1. Raw material
The polystyrene plastics polymerized by the emulsion method use azobisisobutyronitrile as the blowing agent. The residue from the decomposition of azobisisobutyl is toxic, but it has a plasticizing effect on polystyrene. Increasing the amount of dichlorodiisobutyl will increase the plasticizing effect, but the decrease in foam density will be affected. When manufacturing foam with a density of 100kg/m3 or less, a carbonic acid foaming agent is also required. If only ammonium bicarbonate foaming agent is used, the pore structure of the foamed plastic will be poor, which will easily cause coarse pores and uneven pore size.
2. Foaming process
The foaming process is carried out in the extruder.
①The raw material is generally high molecular weight crystalline polystyrene, and the blowing agent is injected from the melting section of the extruder.
②Commonly used foaming agents include butane, alkane, methyl chloride and so on.
③The injected foaming agent is mixed with the melt under the high pressure in the barrel. When it reaches the narrow die of the machine head, the pressure suddenly drops to normal pressure, and the foaming agent dissolved in the mixture expands and foams.
① The extrusion temperature should be strictly controlled during the extrusion process, and the extruded foam sheet should be cooled slowly to avoid excessive negative pressure caused by sudden cooling and cause foam collapse.
The foaming agent is injected into the pressure reduction zone of the barrel, and the molten material is mixed with the foaming agent in a plasticized state, and the pressure is increased. If the extrusion temperature and pressure are controlled within a relatively range, a smaller density can be obtained Soak the plate.
3. Features
The density and cell size of the obtained foam sheet can be controlled by changing the amount of foaming agent and process conditions, thereby preparing foam plastics with special structural properties and thermal conductivity. Compared with the foam sheet made by the expandable bead method, the foam sheet is directly extruded.
Author：admin