Fraunhofer LBF: High-quality surfaces made from recycled plastics

Flawless plastic parts in car interiors, such as ventilation grilles, control levers, armrests, holders, door handles or trims with a high-quality appearance can also be manufactured from recycled materials. However, impurities and material fluctuations lead to visual defects and increased tool wear - problems that make the economic use of recycled materials more difficult. The visual appearance of a component is determined by the surface topography, material composition, coating and processing parameters. Conventional standards describe the textures of injection molded parts, focusing on simple roughness parameters and ignoring the visibility of individual defects. However, the perception of defects is complex: it depends not only on the size of the defect, but also on local reflection changes and contrast ratios such as contrast sensitivity, angular resolution or gloss.

Structuring tool surfaces and concealing defects in recycled materials

In the "Robust" joint industrial research project, scientists from the Fraunhofer Institutes IST, IWM and LBF are developing a suitable structuring of the mold surface so that irregularities and defects in the component caused by recycled materials and fillers are concealed and their use in the visible area is possible. Such structuring of mold tool surfaces, especially with recycled molding compounds, is also of great interest for applications in which high glass fiber contents are added to the compounds to increase the load-bearing properties of the components. In order to contribute to a better understanding between the visual appearance of a surface and its underlying structure, correlations between surface structure and visual appearance or defect visibility of molded parts are also determined and suitable evaluation methods are developed.