Biokomposit för fordonsindustrin : Utveckling och mekanisk utvärdering av hampa/PLA-komposit som klimatneutral ersättning för konventionell PET-plast

Sammanfattning

Global climate change is driving increasing demands on the automotive industry to reduce its environmental impact not only during vehicle operation but also in material production. This thesis, conducted within Polestar's research environment Mission 0 House, investigates the possibility of replacing conventional PET plastic in a vehicle luggage compartment floor panel with a biocomposite consisting of industrial hemp and a bio-based polymer. The study encompasses the manufacturing and mechanical evaluation of composites using polylactic acid (PLA) and polyhydroxyalkanoates (PHA) as matrix materials. Specimens were produced by heat pressing, with PLA composites prepared through carding and PHA composites through a slurry impregnation method. Performance was evaluated through three-point bending tests in accordance with ISO EN 310, climate chamber exposure, FTIR spectroscopy, and a carbon balance calculated from a cradle-to-grave life cycle perspective. Results show that PLA composites with 15–20% polymer content and a density of 400 kg/m³ meet the mechanical requirement of 46 N in laboratory testing, corresponding to a 75 kg point load at full scale. FTIR analysis revealed that climate exposure at 90 °C caused hydrolytic degradation of the PLA matrix and dehydration of hemp fibers, while exposure at 40 °C and high humidity did not immediately affect mechanical performance. The carbon balance demonstrates that the biocomposite achieves negative net emissions compared to conventional PET, provided the material is recovered biologically through anaerobic digestion to biogas. The study concludes that a hemp/PLA composite is a technically and climatically promising alternative to fossil-based PET for automotive interior components, although further studies are required to verify performance under industrial manufacturing conditions and the full automotive testing programme.