One-Step Method for Blow Molding Composites

Now there’s a one-step method of forming lightweight structural thermoplastic hollow sections or hollow articles locally reinforced with continuous fibers. At its German technical center, the High Performance Materials (HPM) business unit of Lanxess is developing methods of placing preheated blanks of composite organosheets in an extrusion blow mold while a parison of the same thermoplastic material is being extruded. When the mold closes and the parison is inflated, the organosheet is formed to shape by the mold and bonded tightly to the parison by the blowing pressure.

The process uses Tepex resin-impregnated, continuous-fiber fabrics from Lanxess’ Bond-Laminates business. These organosheets can be of nylon 6 or 66 (or other resins) reinforced with continuous carbon, glass or aramid fibers. These sheets reportedly bond well in blow molding with Lanxess’ Durethan high-viscosity blow molding grades of nylons 6 and 66 with and without glass fibers. “Even low blow molding pressures are enough to form Tepex into critical 3D geometries such as hemispheres with tight radii,” says Tilmann Sontag, expert in lightweight design at HPM’s Tepex Automotive Group. He adds that the fabric reinforcement makes heated Tepex blanks much easier to handle than unidirectional tapes.

Previously, blow molding with composite sheets required welding flat or preformed Tepex blanks onto the part after blow molding, thus adding one or two extra steps. The new one-step process boasts cycle times “that are typical of blow molding,” states Arthur Rieb, HPM blow molding specialist. The blow molding step determines the overall cycle time.