by Liz White, editor
Polyurethane is now being used as an aid to rehabilitation, in the form of Terrasensa ‘balance’ mats — a new idea from German design company Teo Industriedesign.
These modular mats — an aid for all sorts of physical, medical and sports therapy — are made in squares which push together, designed in endless combinations such that no regular repeats of the surface topography are likely in use, explained its developer Jens Freitag, head of Kassel, Germany-based Teo Industriedesign.
The idea is to present a constantly changing surface to anyone walking, running, jumping or crawling on it, so that the person has to focus totally on their balance.
In aiding balance and stability, Terrasensa “gives users a better sense of their own bodies,” Freitag said.
Terrasensa’s design challenges people to stand and move in a stable fashion. Users have to constantly re-balance and stabilise themselves.
A stroke patient who had struggled to walk upright recovered the ability to do so after just half an hour’s use, Freitag said.
It is valuable in rehabilitation of knee injuries, and Terrasensa can also be used to train older people to balance better and thus avoid some of the injuries and bone fractures that become increasingly common with age.
Ballet training and helping athletes kick well are other uses, he added.
Terrasensa is also finding use in training for high performance sports such as handball, where players are able to train better with the matting than with simple power training, Freitag said.
It is a simple way of helping children and the elderly with physical training, providing a challenge, but in the form of a soft surface so injuries are unlikely, said Freitag.
Pointing out that children learn by moving, Freitag said those who don’t move well are less likely to be smart — so this sort of training helps all-round development.
The PU construction absorbs shock and supports movement: “Polyurethane is the only material for realising this in the way we wanted,” Freitag commented. “PU helps by being indestructible.” When he was designing the device, Freitag said, he wanted a natural effect in an artificial material, and started by modelling rock surfaces by hand.
During the practical step of turning the design into a commercial product, Freitag turned to polyurethane processor Hübner GmbH of Kassel, who is now making and selling the Terrasensa matting.
Delegates at the 10-11 Nov 2009 meeting of the FSK (the German association of foam plastics producers) in Würzburg, Germany, had the chance to test their own stability when the day’s presentations were over – by walking along some samples Freitag had bought along.
PU body for a new GT sports car
German car maker Artega has realised a dream — “to make a new interpretation of a touring sports car,” said Jürgen Pampel, Artega’s marketing manager, discussing the company’s production of a new sports car with allpolyurethane body panels.
Development started 3½ years ago, said Pampel, and it follows work in the 1960s and 70s on models with lightweight composite structures, made in a cost-effective way, he added.
Pampel noted, pointing out that it is “rather small – not longer than the VW Polo.” He described it as the first production vehicle in the world to have all-PU body panels, adding that the next Maclaren model will be the second.
It is, “really suited for daily use,” Pampel said and has had good reviews from the motoring press, comparing it favourably for example, with the Porsche Cayman consumes 8.9 litres per 100 km. “The data are really convincing,” Pampel said.
The 6-gear model uses a VW group engine, and is “completely unencumbered by any brand history,” he added.
Artega is aiming for a “completely new market:” it plans to make 600 cars in 2010, for those who would like a car “that no-one else in town has,” Pampel said.
The roof and hood – parts subject to dynamic strain and also needing higher rigidity — are reinforced sandwich structures, while the other body parts are made using foamed systems, giving a 40-percent weight saving versus steel body panels.
Aluminium parts would be a similar weight, but cost a lot more because of the tools for deep drawing, Pampel said, adding that this is another strong argument for using PU.
The raw materials are practical for the planned production level of 500 to 1000 cars a year, and were developed in close cooperation with BASF-Elastogran.
For the roof module, a paper honeycomb filler gives a component which is both extremely rigid and extremely light. Class A surfaces can also be achieved, said Pampel. The roof principles are applied to the underbody as well, but with an aluminium honeycomb to give high torsional rigidity, Pampel said.
The Artega has an aluminium main frame and a steel sub-structure, with no cast joints, only welded ones. The main frame weighs 85 kg and the whole car weighs less than 1100 kg.
The roof sandwich is glued together automatically and high precision is needed here. Safety is a big issue, so the car has a crash module whose resistance was tested by Conti Safety Systems, and gave excellent results.
A simulated front crash at 50 km/h produced no damage, “a really stunning result,” Pampel commented.
Cost of a standard model is €79 500 ($109 600), said Pampel.
Artega, which employs 63 people, is based in a new plant at Delbruck near Paderborn in Germany. In a recent development, Mexican private investor Tresalia Capital has bought all of Artega from former majority shareholder and managing director Klaus Dieter Frers.
One delegate at the FSK meeting reported a “well-known Munich-based car maker’s” claims that a weight reduction of 20 percent is feasible, but not 40 percent.
Pampel agreed that established car makers say there is no way to reduce weight without safety problems — “which is why the latest Mercedes sports car weighs 1.7 tonnes,” he observed. But he stressed that the Artega has all the necessary safety mechanisms, and that, “its passive safety mechanisms are state of the art.” In discussions, Pampel commented that other car makers are lining up to talk to Artega about its technology, but noted that their objective is for large-scale use, while Artega is only planning small numbers.
Steel uses large presses and deep draw metal technology, and needs a minimum production level of 10 000 or 20 000 cars a year. But, Pampel said, for 1000 units, the PU systems applied to automotive skin parts are “a more economical and cost-effective approach.”
Foam gaskets — now for use outside
Until now, it has not been possible to exploit the advantages of the well-established foam-inplace gasket (FIPG) technology in exterior applications, because the properties of the sealant, which is under mechanical load, are affected by the weather, said Dr Alfred Link of Sonderhoff Chemicals GmbH.
But now Colognebased equipment and materials specialist Sonderhoff has produced a method of making FIPGs with an integral skin, called “Fermaskin” and this opened the door to wider use.
The skin gives very effective UV protection and protects the interior foam from water uptake, said Link, in a presentation at the FSK meeting. The sealant’s mechanical properties are also good, he said.
Foam-in-place gasket technology has been in used for 30 years now, said Link, pointing out that “everyone has seen examples of such gaskets in appliances such as vacuum cleaners and bathroom lamps.” The seal is applied after the appliance casing is moulded. Sonderhoff develops both the equipment technology and the systems for FIPG — some using 2- component systems, although 1-component types are also available, he said.
Fermaskin can be applied using machines similar to those for normal FIPGs, with a mixhead for two-component mixing. The material is applied in a Y shape.
“Water absorption is very low, tensile strength is good, and elongation is very similar to that of sponge rubber,” commented Link.
With the skinned material it is “possible for FIPG to go into new application areas,” he noted.
One of these is electrical switchboards, for example those in desert conditions.
Link said Sonderhoff has worked on a variety of sizes. Long-term UV resistance is good, so the material can be used in external applications, with good adhesive properties, for the first time, he added.
Asked how the UV resistance of the foam is raised, Link said that depends on the individual customer.
Filling a gap in the market
Wood combined with polyurethane may not seem to be a promising mix, but Austrian group Fill Ges.mbH is out to prove that PU/wood composites have advantages that can be exploited in a range of applications.
Part of the logic here is that such work combines Fill’s two basic skills: it supplies process machinery for both wood and PU.
Discussing “Intelligent polyurethane/wood applications,” Fill’s Wilhelm Rupertsberger praised the benefits of wood and polyurethane composites, where the good properties of both materials can be combined and exploited.
In one example, Fill worked with a globally active market leader for wooden formwork beams, to develop a production system for beams with a considerably extended service life — because the cut beam ends are encased in PU, as described in the box above right.
Since the customer bought three systems, this was a successful project for Fill, Rupertsberger noted.
Wood has various advantages: for example it is a renewable natural raw material, and it has a low specific weight, said the Fill executive.
PU’s flexibility in terms of material properties “cannot be beaten,” said Rupertsberger. It is resistant to warping and weathering, the colour is adjustable and it offers great design freedom.
“Why combine PU and wood?” Rupertsberger asked. The answer is that the PU is there largely to protect the wood from damage, for example in edging for furniture such as lips for train tables, which suffer much wear.
Combining polyurethane and wood offers new opportunities in product features and product design, the Fill expert noted.
For wood, limiting the moisture content is important, and it can help to dry the timber shortly before combination with PU, he said.
Using hydrophobic PU systems reduces the risk of blistering and moisture absorption, as do moisture absorbers in the polyurethane system.
It is also useful to pour the polyurethane across the direction of the wood grain, he said.
Co2 for cleaning — and foaming
Mario Curcic of gas supplier Linde AG made some moves to rehabilitate the reputation of CO2, describing some industrial uses of the gas — as a blowing agent (BA) for foam and as a cleaning agent for moulds.
Curcic pointed out that industrial CO2 is a by-product of various processes, and has a lot of uses. It also comes in gas, liquid and solid (dry-ice) forms.
In foams, CO2 is seldom used alone as a blowing agent; usually it is exploited in blends with hydrocarbons, Curcic said.
One advantage of CO2 is its inertness, including lack of flammability, Curcic said. CO2 also has zero ODP and, “almost no global warming potential,” he commented.
It is also, ”pretty inexpensive,” non-toxic, and leaves no residue, added Curcic.
Typical examples of CO2 use might be as a BA for PU backfoaming of carpets, giving PU foam of low weight and density.
A different CO2 use lies in cleaning, which is becoming a standard procedure, Curcic noted.
This uses dry ice, containing no water and having no taste, odour or toxicity, said Curcic.
Why can you clean with CO2? Curcic asked.
Dry ice is at a temperature of -80°C which makes dirt brittle, so that it breaks off. This is a loud process, he commented, because of the kinetic energy involved. An explosive volume increase of the dry ice/dirt of about 500-600 percent occurs: the result is, “perfect cleaning,” Curcic claimed.
CO2 is not abrasive so does not damage expensive aluminium moulds, for example, Curcic noted. Mould cleaning using C02 is becoming standard, especially for sensitive moulds, to avoid expensive damage, he said.
It can also be used in the PU sector for cleaning mould carriers, he said. A logical use would also be to clean moulds using CO2 before applying a [protective] coating, Curcic said.
Acmos Chemie AG, for example, has developed such a protective coating using plasma, which needs the moulds to be cleaned thoroughly before hand.
Curcic also raised the possibility of using solid CO2 for sanding wind-farm rotor blades before painting them, following an earlier presentation on the wind energy sector, noting that “there are application opportunities waiting to be discovered.” Customers making moulded PU parts are also using CO2 in guns, sprayed using compressed air, instead of solvents to remove waxy build-up of mould release agent, he said.
Stone dumping is a tough use
Lining the pipes for stone-dumping ships is a challenging role for polyurethane.
These ships transport and offload stone of various sizes for constructing offshore and coastal protection projects. For deep-water dumping, the stones are unloaded to the seabed destination via flexible fallpipes.
Polytec’s polyurethane machinery and parts business recently developed a two-component roll-coating machine for Dow Hyperlast for such a stonedumping ship, said Peter Stinshoff, managing director of Polytec Industrial Plastics.
BETTER BEAMS WITH COATING
In its wooden beam project, Fill’s customer needed to prolong the beams’ working life. In fact, he initially wanted to get rid of the wooden parts because he needed the ends of the beams to be very strong and wood was not performing too well.
The carrier beams are used to make the formwork for moulding concrete, and are rented out to construction projects.
Fill worked on coating the beam ends with PU to form a shock-absorbing element, and protect the ends against moisture and UV light. In doing so, the PU prevents damage to the beam ends and so prolongs the useful life of the beams.
Together with KraussMaffei, Fill developed a system that involved heating the cut end of the beams to remove moisture, before moulding an elastomeric PU cap over the ends. The wood must have a moisture content below 7 percent, Rupertsberger noted. This helps promote adhesion.
The caps must fit precisely onto the beams and close the wood off tightly: it took a long time to develop an appropriate tool here, Rupertsberger said. Design of the plastic cap and keeping to the required tolerances represented, “A big challenge for our development department,” said Rupertsberger.
Fixed metal fittings could not be used, and instead, Fill and its tooling partner Alba developed the soft fittings which are customised exactly to the wood contour.
Fill also developed the complete robotic system for handling the beams, moving them to a continuously moving rotary table where the moulds are located. Casting takes place at several stations.
Once the moulds are closed, the 2-component polyurethane is poured. After finishing, the timber beam goes round again to have its other end coated with a PU cap.
Fill’s project involved as partners PU machinery expert KraussMaffei, tooling and engineering firm Alba and systems supplier Rampf.
The pipes were 1-m in diameter, and 12-m long, and coating was carried out at a rate of 4 pipes per hour.
The coating had to be durable in order to handle 400-mm stones, dropping at a rate of 6m/s, to a 1400 m depth. This was a “very unique problem,” Stinshoff commented. The coating had to be very hard, with high tensile strength, good tear and wear resistance and good adhesion to steel.
Special challenges included the dimensions and weight of the pipes. The two firms developed the formulations together while Polytec also developed a turning apparatus for the pipes, said Stinshoff.
For roll covers, shrinkage is an advantage, noted Stinshoff, but for pipe lining, it can give adhesion problems and thinner layers of coating may need to be applied. The project involved 314 pipes, and the finished products had 20-mm-thick coatings, said Stinshoff, noting that the business hopes for more of this work.
Polytec Industrial Products consists of Polytec Thelen GmbH in Bochum, Germany and Polytec Elastoform/ Polytec EMC at Marchtrenk in Austria.
Polytec IP uses 1300 kg of polyurethane materials a year and formulates its own systems, to make PU parts. It also produces up to 60 machines a year, Stinshoff said.
It can make cast parts in sizes from 5g to 2.5 tonnes, in one-off pieces or in series of up to 6000 parts, he added.
The business has more than 120 recipes, and can offer customers a range of development options, he added.
Polytec makes large-scale parts for offshore uses, such as buoys, weighing 500-600 kg, made of PU encasing a closed-cell polyethylene foam. Other offshore uses include fenders of up to 300 kg, with many of these needed per boat. For tug boats, the superstructure can be also made of all-PU, Stinshoff noted.PU.
As well as two- or three-component machines EMC can also make high-dosage equipment with two- to six-component potential, dispensing up to 50 kg/min of material.
New mould carrier from Fill
A new electrically driven mould carrier from Austrian group Fill Ges.mbH is eliciting a lot of interest from automotive suppliers, said Norbert Danninger, a sales and project engineer.
Fill’s new Flextra mould carrier can close in only 2 seconds, compared to a normal closing time of 5 seconds, Danninger said, agreeing that this is a feature customers have been asking for. They want to raise throughput and productivity in this highly competitive sector, especially in making automotive instrument panels.
One customer developed a specification and Fill built its first prototype. Three other customers are interested in testing it out in their plants, Danninger said.
Fill demonstrated the new offering at Euromold in Frankfurt last November and the Flextra carrier will eventually go to one of these customers for trials, Danninger said.
Machinery group Fill was set up 1966, and for 30 years has been making mould carriers, conveyors and turntables for the PU sector, for both automotive uses and for the woodworking sector — to make structural parts and beams.
Fill also supplies big presses for the composites industry, for large parts reinforced with glass fibre and carbon fibre.
The family-owned company has 420 workers, an annual turnover of €60 million ($82 million) and exports 70 percent of its production.
In polyurethanes Fill used to have Krauss Maffei as a partner, but is now independent and can go to any maker of PU dispensing equipment for this side of the process.
Fill sees the PU sector as a fast-growing sector of its business: it currently forms just 10 percent of its sales. A typical product might be a mould carrier and a turntable for making moulded seat cushions, Danninger said.
Design and function linked
Display products for jewellery, watches, glasses, technical instruments or wine can made out of a transparent polyurethane with “brilliantly glossy” surface finishes, by the Kling company, said Erik Raus, Kling’s technical manager and director.
A typical part for the company, based in Birkenfeld in the Black Forest, is a bust for a necklace display. Here design and function are closely linked, and branding is also very important for names such as Hugo Boss, for example, said Raus.
Kling bought five CNC (computer numerically controlled) cutting tools and new 3D design software two years ago and worked with PU suppliers to develop materials. The result was clear, individual shapes.
Kling’s technicians can make large volume shapes easily, with no bubbles or airlocks, using vacuum casting with silicone or PU moulds, and an additive to remove the yellow tinge common for urethane.
Next was a move to make highly coloured parts which have proved to be very eye catching – causing people to stop and look at them in window displays, said Raus.
Kling can also cast hollow parts for large volume items, which saves weight and cuts material costs, and has also developed soft-touch coatings and polishing for high gloss. Another use of the technology has been to encapsulate products for point-of-sale displays.