Seamless integration of light and haptics

DirectCoating/DirectSkinning technology meets the requirements of car buyers and manufacturers alike. While consumers prefer a personalised vehicle interior with a premium appearance and an attractive design, the automotive industry is looking to manufacture components efficiently. Interest in this new technology is thus growing steadily and it is now used in series production.

At the K 2016 plastics trade fair, Covestro will be showcasing the prototype of a new design for a steering wheel cover. This development features a wide range of colours, surface structures and tactile properties that can be reproduced on the same component from a single mould using DirectCoating.

One mould for colour, surface and feel

The coated component is produced in a two-component mould using a two-stage process in an injection moulding machine. Having undergone injection moulding in the first cavity, the plastic substrate is then transferred to a second cavity that is one coating layer thickness larger. The solvent-free coating system is injected into this mould via a RIM (reaction injection moulding) mixing head. This creates a polyurethane-coated component with outstanding properties that requires virtually no post-processing.

"Compared with conventional combination of injection moulding and subsequent spray coating, the integrated process offers great potential for reducing logistics effort, energy consumption and space. This and an impressive degree of design freedom is where the significant added value of the process lies,” said Dr Johannes Scherer, head of Covestro’s DirectCoating/DirectSkinng programme.

Virtually unlimited design freedom
The component itself can be transparent, translucent or opaque. Its surface can be coated in various colours, decorated with a matte or high-gloss finish or protected with scratch-resistant functional coatings. There are also various tactile and surface structuring options.

This is another advantage direct coating has over spray coating. The injected coating can also reproduce contours such as sharp or rounded edges and raised surfaces because it accurately depicts the mould surface. Ultrafine grain patterns with a sharp contrast between high-gloss and matte areas are one possible variant.

Located in the driver’s direct field of vision, the steering wheel cover meets the most demanding appearance requirements. The cover’s 3D geometry also demonstrates the flexibility of the process in producing curved surfaces. This can be transferred to other components, too. The development is part of an integrated Covestro material concept for the design of automotive interiors that addresses current trends. The company has developed Bayblend^® and Makroblend^® polycarbonate blends as well as Desmodur^® and Desmophen^® polyurethane coating raw materials for the direct coating technology.

Precise coating filling simulation
Advance computation of mould filling with the polyurethane coating is possible based on a material data set for Moldflow^® simulation created by Covestro. The simulation model considers various influencing factors so that problems such as air pockets can be prevented. Trials with the model have now reached the stage where Covestro is offering its customers and their mould makers the project service of computing the ideal sprue and vent design for the coating component.

At K 2016, Covestro will be showcasing a design variant with a thin illuminated strip that highlights the contour of the steering wheel cover and produces an ambient light effect. This is achieved by leaving the translucent thermoplastic substrate uncoated in the area of the strip. A light source fitted behind the substrate can then shine through the strip to create this delightful visual effect. In a subsequent step, Covestro is planning a combination of DirectCoating with printed electronics, for the purpose of further functional integration.