Polypropylene foam material processing technology
Polypropylene foam materials used in automobiles include polypropylene foam sheets and molded parts made of polypropylene foam beads.
Polypropylene foamed sheet is mainly used as the inner lining soundproof material for car roofs, engine compartments and spare wheel cover. The specifications of the sheet are generally 1.5 to 6 mm, the density is 60 to 150 kg/m3, and the product width is 1000 to 1500 mm. 
The Berstorff PP foam sheet extrusion process is shown in Figure 7. In addition to polypropylene foamed sheet, another type of PP foamed product is used in automobiles, namely molded parts molded from PP foamed beads, including sun visor, headrest pillow, door inner panel, Bumper energy absorption block, spare seat etc. Berstorff's technology in this area is to process solid PP pellets into extruded EPP foam pellets with a density of 15 to 100 kg/m3 by extrusion. These pellets can be processed into various parts by steam molding equipment. Parts (as shown in Figure 8). 
FIG. 8 shows the process flow and equipment configuration of the PP foam beads EPP foam bead extrusion equipment. As shown in FIG. 9, the PP foam bead material production equipment is shown in FIG. 10. 
In the process of extruding foamed beads, the foaming agent used is butane, which can achieve a maximum foaming ratio of 60 times. The diameter of the obtained pellets is between 3 and 5 mm (Figure 11). Show). 
In the process of extrusion processing of the entire bead material, the core of processing lies in the two steps of extrusion and pelletizing. For extrusion, the temperature and pressure of the melt at the end of the extruder and the dispersion of the blowing agent are required to reach a very uniform and stable level, and the pelletizing process must take into account the mastery of the particle foaming process. The particle uniformity of the pellets and the mechanical fit of the pelletizing system.
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