additives feature | Natural fi bres Harsh screw design Softer screw design
Graphs 1 and 2: Comparison of the processing window of different screw designs as calculated using SCC’s Ludovic software. The more green, the wider the window. Green axis: residence time; red axis: screw rotation speed; blue axis: material throughput
the extrusion process to obtain the best processing window for Woodforce. “Natural fi bres are sensitive to the temperature and the shear generated by the process conditions. The defi nition of the processability window is thus a key issue for granting the mixing quality,” says Laurent Ratte in sales and marketing. In order to improve the processability of natural
fi bres, the identifi cation of their maximum processing temperature and their optimal shear rate/energy for the best fi bres dispersion is key to optimizing their fi nal characteristics and the quality of the fi nal product, Ratte says. The Ludovic program uses input data from alterna-
Inno-Comp is developing wood fi bre reinforced compounds for applications such as auto interior components
tive screw designs and process conditions, which it tests using Design of Experiments (DoE) to identify their infl uence on the key characteristics of the fi bres. The software then outputs the temperature and shear evolution curves for each confi guration. It also com- putes a global energy balance of the system in order to track the dissipated energy and the deformation caused to the fi bres. Analysis of the parameters helps in fi nding the right compromise between mixing effi ciency and fi bres conservation, says Ratte. “Ludovic provides tools for an effi cient identifi cation
of the process mechanisms and the constraints undergone by the material and the fi bres,” Ratte says. The DoE is based on numerous simulations to defi ne a
surface indicating the suitability of the process condi- tions. Graphs 1 and 2 show how the same processing conditions have been tested on many screw designs. The harsher the screw design, the narrower the processability window.
EU funded projects The European Union (EU) is sponsoring numerous collaborative projects to try and kick-start technologies for producing and processing bio-based materials. ECOplast is one of them, with the formal title of “Research in new biomass-based composites from renewable resources with improved properties for vehicle parts moulding.” Begun in 2010, its results will be published in June. ECOplast deals with the development of novel
biocomposites having biopolymers as base matrix, reinforced with natural fi bres, as well as nanofi llers, mineral fi llers and additives. The project involves the development of several new reinforcements and novel additives, including treated natural fi bres (nanocellu- lose) for enhancing the dimensional stability and the mechanical resistance. One important goal in this project is the adaptation
of conventional compounding techniques and the design of new ones tailored to biocomposites. According to ECOplast, “the challenge here will be to overcome the problem of degradation due to extreme thermal conditions and moisture absorbency”. The project is being coordinated by bioplastics
compounding specialist FKuR Kunststoff. This company has already developed a wide range of compounds primarily made from natural resources. It works in cooperation with the Fraunhofer Institute UMSICHT which is also involved in the ECOplast project. Examples of FKuR’s compounds include Fibrolon wood-plastics composites that can be injection moulded, a process that can be problematic for typical WPCs. Other participants in ECOPlast include the Finnish
16 COMPOUNDING WORLD | March 2014
www.compoundingworld.com
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