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Powder coatings provide several advantages over traditional coatings: environmental friendliness, freedom of design, robustness and resistance of surfaces, possibility to seamlessly all-around coating, fast production process, cost-effectiveness. In the last years these benefits of the powder coating technology have been adopted from metal to heat-sensitive natural fibre/ wood based substrates (especially medium density fibre boards- MDF) used for interior furniture applications. Powder coated MDF furniture parts are gaining market share already in the classic furniture applications kitchen, bathroom, living and offices. The acceptance of this product is increasing as reflected by excellent growth rates and an increasing customer base. Current efforts of the powder coating industry to develop new powders with higher reactivity (i.e. lower curing temperatures and shorter curing times; e.g. 120°C/5min) will enable the powder coating of other heat-sensitive substrates like natural fibre composites, wood plastic composites, light weight panels and different plastics in the future. The coating could be applied and cured by the conventional powder coating process (electrostatic application, and melting and curing in an IR-oven) or by a new powder coating procedure based on the in-mould-coating (IMC) technique which is already established in the plastic industry. Extra value could be added in the future by the functional powder toner printing of powder coated substrates using the electrophotographic printing technology, meeting the future demand of both individualization of the furniture part surface by applying functional 3D textures and patterns and individually created coloured images and enabling shorter delivery times for these individualized parts. The paper describes the distinctiveness of powder coating on natural fibre/ wood based substrates, the requirements of the substrate and the coating powder.
Critical size bone defects and non-union fractions are still challenging to treat. Cell-loaded bone substitutes have shown improved bone ingrowth and bone formation. However, a lack of methods for homogenously colonizing scaffolds limits the maximum volume of bone grafts. Additionally, therapy robustness is impaired by heterogeneous cell populations after graft generation. Our aim was to establish a technology for generating grafts with a size of 10.5 mm in diameter and 25 mm of height, and thus for grafts suited for treatment of critical size bone defects. Therefore, a novel tailor-made bioreactor system was developed, allowing standardized flow conditions in a porous poly(L-lactide co-caprolactone) material. Scaffolds were seeded with primary human mesenchymal stem cells derived from four different donors. In contrast to static experimental conditions, homogenous cell distributions were accomplished under dynamic culture. Additionally, culture in the bioreactor system allowed the induction of osteogenic lineage commitment after one week of culture without addition of soluble factors. This was demonstrated by quantitative analysis of calcification and gene expression markers related to osteogenic lineage. In conclusion, the novel bioreactor technology allows efficient and standardized conditions for generating bone substitutes that are suitable for the treatment of critical size defects in humans.
