KraussMaffei will be marrying thermoplastics and reactive process machinery in one of the more interesting technology demonstrations at K2016 in Düsseldorf, Germany, Oct. 19-26.
In a collaboration of nine partners, polyamide 6 frames for the roof shell of a demonstration sports car will be produced at the KM exhibition booth several times a day on a resin transfer molding press (RTM) of just 350 metric tons. Normally an automotive injection press for structural parts would require a significantly larger clamping force. In another innovation, the part produces near net shape in a reactive process, saving valuable carbon fiber as well as production time and cost.
The trick of the trade is the polymerization of caprolactam into polyamide 6 inside the mold.
A pre-shaped semifinished product made of fiber layers is infiltrated in a mold with caprolactam infused and mixed with activator and catalyst.
“The Roadster roof frame is based on a hybrid construction of fibers in conjunction with plastic and metal. The production process on the KraussMaffei K 2016 exhibition booth will last about two minutes. The system is intended for high-volume projects and is designed for multiple-shift operations,” says Erich Fries, head of the Composites/Surfaces business unit at KraussMaffei.
Called T-RTM, KM says the process has benefits over traditional RTM with epoxy resin or polyurethane (PUR). For one, water-like viscosity allows the caprolactam to penetrate the fiber layers even with low internal mold pressures. Also, the high flow capacity allows the minimum wall thickness to be reduced and the fiber volume content increased by about 60 percent.
The thermoplastic parts can be reheated and reshaped, making them weldable and recyclable, according to KraussMaffei. The roof frame material can be regranulated and used together with its fiber portion to produce parts.
In another interesting attribute, KM says that polyamide 6 has higher impact strength and more ductile fracture behavior than thermosets.
Development partners include KraussMaffei, Forward Engineering (component design, hybrid concept), Alpex Technologies GmbH (T-RTM mold), Dieffenbacher (production of preforms/handling), Saertex (fiber layers), Henkel (bonding), Handtmann (aluminum inlays), TUM / LCC (fiber selection) and Keller (extraction technology).
The concept of polyamide (or nylon) reaction molding dates back to 1982 when Monsanto invented RIM nylon, or Nyrim, which is an elastomer-modified polyamide 6. The material was commercialized by DSM and later is now owned by Brüggemann Chemical of Germany. The material’s high cost compared to traditional RIM materials led to slow acceptance. Krauss Maffei hopes its approach, particularly automation of the process, will be more economical.