Simulation-assisted optimization of recycled-based nylon compounds

Nowadays, sustainability is the most relevant target to achieve among big production companies, both to respond to market drivers (i.e., costumers are becoming aware of the health and environmental impact of the products they buy) and to stick with the more and more strict environmental policies imposed by governments all around the world. In almost every company, one way to increase sustainability as well as profit is to improve efficiency, i.e., reduce the amount of waste, by adopting digital solutions that can enhance production performances while reducing energy consumption. On the other hand, productive companies may use more hardware solutions such as the implementation of renewable energy sources for their plants but most importantly, focus their effort on recycling materials! This approach is embraced by Radici HPP, with which this work has been done. More specifically, Radici HPP possesses a dedicated products portfolio of recycled material coming from both post-industrial recycled, PIR, and post-consumer recycled, PCR, goods. This product line is commercially available and known as Renycle. The aim of the present thesis is to assess the potential use of a digital tool, i.e., a 1-D CFD simulation software, Ludovic®, to improve the production efficiency of Renycle class. Indeed, the simulation software presents intrinsic limitations related to the level of simplifications (e.g. 1-D flux, neglect of the impact of fibers on rheological behaviour, etc.) needed to run the simulations with a reasonable computational effort. Moreover, recycled material properties have high standard deviation since they come from different uses and purposes, hence, the mean properties (used as input in a simulation) are not good representative data. Therefore, it is necessary to assess the use of a digital tool with intrinsic limitations (even though proven perfectly valid for virgin material) to recycled material. The study is carried out on two different polyamide 6-based compounds having 30% and 35% w/w fiberglass, respectively. Different temperatures (240-260-280°C) and screw speed (350-450-550 rpm) were simulated, and the final production parameter choice is the optimum point between glass fibers breakage (related to mechanical performances), energy costs. The results were normalised accounting for polymer degradation which cannot be simulated. For this purpose, tensile stress at break, tensile strain at break and notched and unnotched impact strength tests were done. The compounds are eligible only if the values of the four characteristics are above or between threshold values. In both cases mechanical properties were acceptable for purchasers: this can be translated in a low glass fibres breakage as predicted by Ludovic. On the basis of the results obtained therefore the software has been considered suitable for recycled polyamides 6-based compounds optimization.