With emphasis on weight reduction throughout the transportation industry, there is a renewed effort to remove as much mass as possible to improve vehicle performance. JSP has developed and optimized a blow-molding process that combines traditional blow molding with an injection-molded particle foam core. This process, called Foamcore, utilizes traditional blow-molding equipment combined with a particle foam injection unit to produce a composite blow-molded part with a solid foam core.
JSP's Foamcore technology allows for simpler designs, higher strength-to-weight ratios, and lower part weights, all while using existing tooling (with minor modifications). Multiple polymers can also be used, including polypropylene (PP), polyethylene (PE), polystyrene (PS), and others, for both skin and core materials.
This paper will describe recent advancements of this technology, and how they allow for improved mechanical properties to be realized in the area of transportation applications for structural and semi-structural components. Other features discussed include improvements in thermal insulation and sound abatement, as well as recyclability and end-of-life requirements.
JSP's Foamcore technology is a hybrid combination of traditional blow molding and expanded bead-foam compression steam-chest molding. Using this method, a blow-molded part can be produced with a self-contained foam core consisting of PS-, PP- and/or PE-based particle foams. This technology allows the production of single-layer traditional blow-molded parts with a foamed inner core in a single shot.
Traditional extrusion blow molding begins with extruding the base resin to form a parison, which is drawn down between two mold cavities. The parison is then clamped between the closed mold cavities, and air is blown into it (via one or more blows) to form the cavity. The action of the air, with the help of external vacuum assist (on select portions of the tool), allows for the formation of the part. In some cases (for structural parts), moving slides are used to form internal ribs, or "tack-offs," which give the part structural support. Once the plastic has cooled and hardened, the mold opens up and the part is ejected.
Blow molding can consist of a single layer or multiple layers of different resins or combinations of resin blends. In the case of structural blow molding, a single layer is generally used. In order to control the structural rigidity of the blow-molded part, the parison thickness can be controlled, resulting in a controlled part thickness for additional support. Resin fillers can also be used. Many structural blow-molded parts using PP or PE (including HDPE, HMWPE, and UHMWPE) also add chopped glass or other mineral fillers (talc, etc.) to achieve different levels of structural support.
The Foamcore process uses traditional extrusion blow molding technology using the accumulator method to drawn down the parison. After the mold is closed and the parison is blown to form the cavity, the Foamcore technology is engaged. The basic steps are as follows: (1) blow molding, (2) puncturing cavity, (3) filling bead foam, (4) steaming, (5) cooling, and (6) ejection.
Figure 1 illustrates the basic steps of the Foamcore process. All of these...