Energieverbrauch beim Recycling von glasfaserverstärkten thermoplastischen Composites: Eine Gegenüberstellung des einstufigen und zweistufigen Spritzgießcompoundierens

Nowadays, energy savings have become an essential issue, as they have a positive impact on the environment and on the manufacturing costs. Furthermore, recycling is also an important topic from an economic and ecological point of view, especially regarding resource saving. For this reason, the increasing production of plastics requires efficient and sustainable recycling. Glass fiber-reinforced thermoplastic composites (GFTC) are considered important materials for lightweight construction, as the reinforcement improves the mechanical properties while keeping ensuring low mass. In this work, single-stage and two-stage injection molding compounding processes were compared in terms of energy consumption. While the conventional two-stage process consists of separate compounding with granulation followed by injection molding, the single-stage process combines both steps. By melting the polymers only once, energy consumption should be reduced and the thermal load on the material minimized. The primary objective of this study was to investigate whether integrating both processes results in a measurable energy improvement compared to the two-stage process. To address this question, several experimental series were conducted with different material compositions and process parameters. Five test series were used to analyze the energy data. Descriptive statistics and significance analysis were applied to evaluate the recorded power consumption regarding the effects of material composition and process parameters. During compounding, no significant differences were observed, except for two material compositions where inactive cooling and its consequences caused deviations. For the other material compositions, no notable differences were detected. More pronounced deviations were observed at the injection molding machine. In the single-stage injection molding compounding process, the material was already fully molten when entering the machine, which led to rheological effects and significantly increased motor power consumption. Initial assumptions suggested that increasing the cylinder heating temperature would raise the required heating power; however, this could not be confirmed by the measurements. The comparison of the two process variants made it clear that, for a more precise evaluation, the existing process instabilities would have to be eliminated and the process parameters standardized. At the same time, it was determined that energy savings would be possible. The findings provide a basis for future research projects and contribute to making plastics processing more energy-efficient and sustainable.