K 2013 saw automotive polyurethane collaborations

By Simon Robinson

One of the most notable features of the K show in 2013 were automotive cooperations. They brought together a number of companies using polyurethane as either the main component or a vital part of component production. The developments were driven by the production advantages and material properties that polyurethane has over conventional materials and other polymers.

Three companies, Magna Steyr, Rühl Puromer and Hennecke have developed an engine bonnet with a honeycomb core, which meets automotive specifications, is substantially lighter and provides superior thermal and acoustic insulation to conventional bonnets made from steel or aluminium, Hennecke said.

In 2009, the EU published Global Technical Regulation (GTR) no. 9 on pedestrian protection, this is driving automotive innovation at a number of automotive manufacturers and suppliers around the world, said Hennecke. Pedestrian protection is also assuming greater importance in redefining Euro NCAP ratings, a non-manufacturer-specific crash test programme.

Hennecke said that to receive 4-star or 5-star ratings for their vehicles, manufacturers must make greater efforts to ensure pedestrian protection. The engine bonnet is critical. It should be designed to absorb as much energy as possible in a collision with the body. This requires free space underneath the bonnet. In current motor vehicles, all of the space in the engine compartment is filled.

Hennecke added that as a result, manufacturers have developed quick-acting systems that raise the bonnet in a collision while some are fitted with additional airbags. These are expensive, technically complex and need maintenance. They also take up more space and need design compromises to work.

Magna Steyr, part of Magna International, used its expertise in sandwich technology to develop and produce exterior parts in series, said Hennecke.

The resulting fibre composite bonnet has been produced with support from Ruhl Puromer and Hennecke. It is based on using fibre-reinforced polyurethane in an interlaced paper honeycomb structure.

The bonnet needed to meet Class A surface standard.

Ruhl Puromer from Friedrichsdorf, Germany, developed the PU system and Puropreg system to make honeycomb sandwich support structures. Ruhl also developed Purorim, which uses a Reaction Injection Moulding (RIM) process to ensure the required surface quality.

Hennecke’s PURSeite PU mixing and metering system was chosen to process the materials.

After the development period, series production of the bonnet is now imminent.

Hennecke said that, in principle, the sandwich structure of the bonnet resembles the design of a load-floor for luggage compartment system. A honeycomb core is used for the production of the bonnet, with glass fibre reinforcement applied from above and below. To achieve the different compression hardnesses and stability required in the bonnet, as might be needed for hinges, the honeycomb core is designed as a reinforced structure at the relevant points, Hennecke said.

Afterwards, the PU matrix is applied using the PUR-CSM spraying process. In this patented spray-up approach, the semi-finished fibre products are wetted on both sides with a thermally activated PU system. This makes it possible to apply a thicker layer of material in specific, targeted areas of the component. The part is then compressed and cured inside a mould. In the next stage, the RIM process is used on the outside and around the outer edge of the bonnet to produce the paintable class-A surface.

The polyurethane spray coat creates a durable connection between the glass fibre and the honeycomb core, which ensures extremely high stability and torsional rigidity. The thickness and structure of the honeycomb core allows the crash performance of the bonnet to be adjusted as needed. If the bonnet is designed to extend down to the radiator grille at the front, this area then also corresponds to the regulations for pedestrian protection and allows the designers almost total freedom to design the front section of a vehicle.

The structural design includes other positive effects. In addition to the substantially lower weight, the bonnet has excellent insulating properties thanks to its honeycomb core. A noise-absorbent mat, which is almost inevitable in conventional bonnets, is not needed.

It also thermally insulates the engine and means that cold starts can be reduced, meaning lower CO2 emissions.

The bonnet has passed all of the comprehensive approval tests for use in the automotive industry – and naturally also the new requirements for pedestrian protection.

KraussMaffei was demonstrating a glass-reinforced polyurea process that allowed the roof part to be painted directly after moulding. This makes automotive part production “considerably easier because there is no need for intermediate processes such as priming and pre-painting,” said Nicolas Beyl, head of the Reaction Process Machinery division at KraussMaffei.

He added that “there is no need for manual work such as polishing and smoothing. It also significantly reduces costs.”

A roof panel for the Roding Roadster R1 lightweight sports car was being produced live at the show. The roof panel is made from a CFRP endless fibre in a quasi-isotropic configuration and has a surface area of about 0.6 m2. The part is 2 mm thick and its surface material is 0.2 mm thick. It has a fibre content of around 50%. A Henkel PU system is used as matrix material. A Ruhl Puromer aliphatic polyurethane system forms the special surface coating, which is also UV stable.

KraussMaffei added that cycle times are fast because the resin reacts quickly and speedy clamping movements give short process times and consistently high component quality.

Two RimStar Nano 4/4 metering machines equipped for high-temperature processes – in which material temperatures can reach up to 80 °C – were used to prepare the polyurethane resin matrix. The wear-optimised design of the pumps in the RimStar pumps are designed to be wear-resistant and to give long-lasting process reliability with current polyurethane matrix systems. The machines have de-gassing storage tanks and a precise, energy-efficient temperature control system right up to the mixing head.

Polyurethane is poured into a slightly open mould which then closes ensuring good fibre wet-out and helps to keep the fibres in place. The high-pressure mixing head is self-cleaning, says KraussMaffei, and this helps to improve product consistency. The variable nozzles allow pour rates to be altered mid-shot without changing pressure or quality, says KraussMaffei.

Additionally, the heated RIM mould has vacuum assistance and a seal to help improve the part quality, says KraussMaffei.

KraussMaffei used K to show how its Spinform technology could use polyurea to save customers money and produce good quality, polyurea-coated automotive components. The firm was showing an example automotive part produced on the GXW 550-2000/380 multi-component SpinForm

injection moulding machine with swivel plate technology. The machine’s injection unit made a thermoplastic substrate from a polycarbonate blend, which was then flow-coated with two different polyurea coatings. The coatings are certified for the automotive industry and produce a first-class finish, said KraussMaffei. The firm added that the technique allows openings to be made and the mould surface to be shaped exactly to the part. This combination, allows polished structural surfaces with a precise edge to be made, said the firm, which added that 3D effects with transparent coatings can be achieved in a single work step.

“Our processes reduce the cost of manufacturing premium-quality part surfaces by

30% compared with conventional multi-stage processes,” said Frank Peters, vice president sales at KraussMaffei.

Polyurea coatings were metered into the mould with a RimStar Nano 4/4 reaction process machine equipped with new wear-resistant pumps. The mixing heads mounted directly on the machine meter the polyurea coating into the mould cavity extremely accurately, said Peters. This ensures that it is distributed completely evenly over the substrate without overspray. Further advantages of the new unit are that its installation area is about 30% of the previous model and that its operability has been optimized for the ColorForm process.

Another benefit of the machine is that because all of the components for the part are produced in it – in one process – there is no need for stocks of semi-finished components and the associated logistical systems.

Once again cooperation between a number of specialists was part of the development: Hofmann developed and supplied the mould technology for automated plastic component manufacture. Thermoplastics came from Bayer MaterialScience, while the polyurea coating systems were developed and supplied by Panadur.

Part structuring and design was taken care of by Weidmann Plastics Technology said Peters.

Finally, a four-way cooperation between Korea’s Huyndai Motors, Austria’s Engel, Germany’s Hennecke and Germany’s GK Innovation Concept Tooling have developed Varysoft, a process that GK Innovation calls a unique method of producing padded, soft-touch automotive interior components.

Speaking on the side-lines in Hall 15, Roger Kaufmann, director, GK Innovation Concept Tooling, explained how the innovation happened: “We started thinking about this process six years ago, about 18 months ago we were approached by an IP expert at Hyundai Engineering to look at the concept, to see if we can make it cost effective.” He added: “We have a relationship with Huyundai which goes back about eight years.”

The idea grew out of earlier work that GK Innovation had done around applying copolyester TPEE foils to PC/ABS structural components. In this, the PC/ABS armature is moulded and then the copolyester foil is added and the mould is closed, after a short period of time the mould is opened by a few millimetres. This gives the copolyester room to foam and produces a soft touch finish.

The new process uses polyurethane from BASF to weld the foil to the armature. This gives the

The Varysoft workstation comprises an Engel injection moulding machine, producing the armature in PC/ABS, a thermoforming station. This grains and trims the foil to fit into the mould and a Hennecke polyurethane dispensing machine.

The mould set-up is slightly complex and made of a number of zones, despite this, it is relatively inexpensive, said Kaufmann. “High pressure is only used on the injection side of the mould, the rest is low pressure processing,” he explained.

In the process, the armature is moulded at the same time as the foil is formed and shaped. Once the moulding is ready the foil is placed in the second part of the moulding set-up and the armature side rotates to sit behind the foil. Polyurethane is then injected into the void between the armature and the foil bonding the components together.

“We worked with Engel on the project because we share patents around the Dolphin injection moulding technology. Its head of automotive applications, Michael Fisher, is a very forward-thinking person,” said Kaufmann.

Kaufmann said his firm had no previous experience of polyurethane moulding and so Engel spoke to Hennecke. He explained that Hennecke bought its parent company, BASF into the project to supply polyurethane. Hyundai introduced Moltex as the thermoforming components company, and foils are supplied by a third party from Korea. The PC/ABS blend is supplied by Ria Polymers

Although there could be capital costs involved in setting up the system, said Kauffman, automotive component suppliers could save money in a number of areas. This process would reduce inventory and simplify component supply because there is no need to keep track of individual sub components. Production steps are reduced because all of the processes needed to produce the component are in a single space. Additionally, there can be space savings: “We’re going up against slush moulding with this,” said Kaufmann, “the footprint of this setup is small in comparison.”