Molten handling compatible with material flow
In the joint venture on materials and long-term properties in recycled materials, Fraunhofer LBF is laying the foundations for increasing the rate of polymerase chain reaction (PCR) for industrial applications in technical plastics. The objective is to find out the dependencies between the composition of the input materials, the influencing factors during formulation and the resulting application properties.
The aging properties of post-consumer recycling (PCR) materials are being evaluated early in the development phase as part of the new joint venture. © Ursula Raapke, Fraunhofer LBF
The plastics industry expects viable and practical solutions that significantly increase the proportion of recycled materials, even in technically demanding applications. While post-consumer recycled (PIR) materials still have a very specific composition, the variety of possible combinations (such as foreign polymers, non-plastic parts, additives, adhesives) and aging cases for post-consumer recycled (PCR) materials is very high and subject to To change regional and seasonal fluctuations at least. These also have an impact on the resulting product properties. For example, processability and mechanical properties generally deteriorate with increasing percentage of PCR in the composite or in the product made from it.
The aging resistance and thus the service life of the composite is largely determined by its composition. The flow condition of the materials used and the sorting, separation and processing techniques used determine the quality of the resulting recycling. The complex also has various options to further improve the quality and properties through various measures. For example, through (re)targeted addition or through the proportional use of new materials.
Even the identification and evaluation of suitable extruded secondary materials, such as graded and cleaned or re-grinded chips, requires a significant amount of effort. Downstream steps, eg b. Characterization or quality control, and homogenization are also expensive and often associated with the security of large batches. Complexity increases again due to variables in composition (formulation, process). It is often only apparent late in the development or improvement cycle whether target properties (such as mechanical properties and aging resistance) are achieved as a result and whether they are also reliably controlled by other variables, such as batch-to-batch input material flows . Today, this is often done using the trial and error method.
© Ursula Raapke, Fraunhofer LBF
Identify dependencies early
The objective of the new joint venture is to gain extensive knowledge of the dependencies between the packaging form (eg granules, re-grind), the chemical composition of the input materials, the influence on variables during formulation (eg the ratio and state of recycling, re-additives) and to develop the resulting application properties, particularly with regard to With mechanical behavior and aging resistance. This is done using the example of selected densification polymers used in technical applications, such as polyamide (PA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or polycarbonate (PC). At the Fraunhofer Institute for Structural Robustness and System Reliability LBF, typical and representative installations are produced using selected recycling materials and selected additives, taking into account typical requirements profiles established with the project participants. The recycled materials used are described in detail previously with respect to molecular parameters relevant to the processing and application properties.
The focus is on chemical composition (in terms of polymer and foreign matter content), additives, and molecular weight distribution. Based on these results, structure and ownership relationships are derived. The dependencies of mechanical and rheological properties as well as long-term properties, such as aging behavior, need to be better understood when using PCR for selected technical thermoplastics. In addition, these results serve to estimate or predict similar combinations.
Project partners are required from the industry
The project is open to other industry and business partners. Interested parties can find details about contact points and other procedures at the following link: www.lbf.fraunhofer.de/rezyklat properties