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High-tech padding with a tailor-made skin

Bayer MaterialScience AG : 14 October, 2004  (Company News)
In recent years, viscoelastic (VE) foams have become a further powerful variant in the broad range of standard and high-resilience (HR) molded foams. The market leader in polyurethane raw materials,
Bayer MaterialScience AG, is now once again extending the range of application of these slow recovery foams by intelligently combining a high-quality VE foam from the Bayfit® program with the easy-to-apply, plasticizer-free, yet highly elastic polyurethane spray elastomer Baytec® Reactive. Combining these two high-tech materials has yielded VE foams that marry the superior qualities of a viscoelastic product with a particularly hygienic, sealed surface.

“Viscoelastic foams are in the process of expanding into more new areas of application,” says Dr. Ralf Güther, polyurethanes expert at Bayer MaterialScience. “They show a slower recovery at higher deformation than corresponding HR foams and adjust superbly to every contour. This means that the weight of any body resting on it is distributed over the largest possible area. The innovative VE foams have therefore recently found use in high-quality furniture for homes, offices and public areas, where they provide improved grip and a pleasing 'wow factor' when people sit down. However, the medical sector remains an important area of application.”

The material’s medical properties include not only excellent pressure relief (which is important for combating bedsores), but also optimized hygiene characteristics. “Up to now, waterproof covers made of, for example, PVC were applied to the foams post-production to protect them against liquids,” says Dr. Güther. “However, large amounts of plasticizers must be added to these covers if their elasticity is even to come close to that of the viscoelastic core. By applying a tailor-made skin of high-grip Baytec® Reactive polyurethane spray elastomer directly during manufacture, users can now permanently seal the hygienic, viscoelastic Bayfit® padding without having to cover the foam with the vulnerable film in a laborious post-production step. The customer is also spared the problems arising from the gradual embrittlement of the PVC caused by the plasticizers migrating or being washed out.”

All that’s required to produce the long-life foam/spray skin composite is to firstly spray the filler-free Baytec® elastomer into an open mold, using robots if necessary. Since the material’s special thixotropic formulation prevents it from running down the upright face of the mold, it can also be used for products with complex geometries. The high mixing viscosity is achieved without compromising the reactivity of the formulation. If especially robust zones are required, the thickness of the spray skin can be varied between 0.2 and several millimeters - even on a single product. The skin’s final hardness can generally be formulated between extra soft (35 Shore A) and extra hard (60 Shore D). Favorable isocyanate/polyol mixing conditions that are largely unaffected by mixing fluctuations in the metering unit make for a low-waste production process.

Once the spray skin has been applied, a liquid mixture of polyurethane raw materials is filled into the mold. The ensuing reaction yields a viscoelastic foam with optimum cell size distribution. The result is a foam/elastomer composite in which the viscoelastic core is sealed against air and moisture, and is responsive to all the user’s movements.

“With truly high-tech foams like these, customers benefit from the expertise we and our partners in the polyurethane industry have honed over decades working with this versatile family of plastics,” states Dr. Güther. “Our experience in this field is unmatched by any other raw materials manufacturer in the world. To ensure in the mid-term that end customers as well as foam manufacturers and designers are aware of this technological lead, we are increasingly marketing our flexible foam raw materials and systems under the Bayfit® logo with the motto “foam your ideas” and, tailored to different user industries, under the Bayfit® Home, Office, Public, Medic and Tec brands. The example of our raw materials for viscoelastic foams, which we can formulate on the basis of either TDI or MDI, is a clear indicator of the development expertise which the foam sector can expect from a research-driven company like Bayer MaterialScience.”
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