New RTM technology uses thermoplastic matrix system

• T-RTM technology enables the use of thermoplastic matrix systems in the RTM process for the first time
• Suitable for the mass manufacturing of automotive components
• First application: B-pillar reinforcement prototypes at VW

As one of the few companies in the market, KraussMaffei is in a position to offer machines and moulds for processing both thermoplastic and thermoset matrix systems. The most recent example is the further development of the RTM process to enable it to be used with thermoplastic matrix systems, something that has not previously been possible, according to the company.

The thermoplastic challenge: pore-free impregnation of the dry semi-finished fibre product

The high automatization potential of the RTM process makes it particularly suitable for the mass manufacturing of automotive components made from fibre-reinforced plastic. Until now, this technology has primarily been used to process thermoset matrix systems, such as epoxy resin. The use of thermoplastic matrix systems, which are generally more cost-effective than thermoset ones, has not been possible. This is mainly due to their comparably high viscosity when in a molten state, which more or less prevents pore-free impregnation of the dry semi-finished fibre products under acceptable processing parameters. In cooperation with Volkswagen AG and BASF SE, KraussMaffei has now succeeded in transferring the use of thermoplastic matrix systems to the RTM process.

First products: B-pillar reinforcement prototypes made at TechCenter of VW

In the so-called T-RTM process, a low-viscous, reactive caprolactam system is injected into a closed, isothermally heat-balanced mould that is lined with endless fibre-reinforced semi-finished textile products, where it is then polymerized into polyamide 6. The polymerization process takes place after the fibres have been saturated. The first products to have been manufactured using the T-RTM process are B-pillar reinforcement prototypes made at the FRP TechCenter of the Volkswagen Group Research Center in Wolfsburg, Germany.

A basic requirement for successfully developing the T-RTM process was an adaptation of the caprolactam systems currently in use. In addition to the required activator and catalyst, they also contain a number of additives and admixtures, which are later used to form the matrix systems adapted to FRP components. A metering machine specifically adapted to process the extremely low-viscous system was also required to ensure that the manufacturing process runs smoothly. The mixing and metering machine is fitted with a special mixing head, high-performance axial pumps and a fully electric temperature control system.

KraussMaffei will present the new T-RTM technology at the upcoming Composites Europe show in October. In addition, the company will also show its surface TRM process for the production of paintable fibre-reinforced components and FiberForm, a processing technology that combines injection moulding with thermoforming of composite sheets.

Photo: RimStar-series mixing and metering machines for the processing of epoxy resin, polyurethane and polyamides. The machine has been adapted for the T-RTM process and the extremely low-viscous material used.