Recycling of space food packaging for production of polyethylene tools by additive manufacturing

Long-duration interplanetary human missions require careful planning and management of resources such as fuel, water, food and spare parts. Resupply missions may not be feasible, necessitating efficient resources utilization and recycling. Additive manufacturing (AM) technologies play a significant role not only in the field of extraterrestrial infrastructures construction, but also in small components or spare parts production. In this work, we investigated the possibility of recycling space food packaging into a new composite material based on low-density polyethylene (LDPE) filled with PET-aluminum-LDPE (PAL) trilaminate. LDPE was recovered from septum adapter and straw, while PAL trilaminate was obtained with the entire beverage packaging. Due to the limited availability of space beverage packaging, septum adapter and straw material were simulated by LDPE powder with a particle size of 500 μm, while commercial coffee package was used as surrogate of the entire trilaminate wrapping. At first, as proof of the similarity between the thermoplastic layers which characterize the coffee packaging composition and those of the space beverages, a chemical behavior investigation was performed by Fourier-transform infrared spectroscopy (FTIR). Furthermore, raw PAL trilaminate was milled and sieved to be mixed with LDPE. The thermal properties of this new filler were investigated by differential scanning calorimetry (DSC), while the average grain size was preliminarily carried out via scanning electron microscope (SEM) and more thoroughly by Bootstrap resampling technique. Then, specimens were produced via casting process by melting the composite powders in oven while degassing. Different weight percent (wt%) of PAL trilaminate filler (5 and 10 wt%) were incorporated to LDPE matrix. Two different groups of specimens were produced, for performing dynamic mechanical analysis (DMA) and thermal conductivity evaluation. During dynamic mechanical analysis of composite specimens, a slight decrease in storage modulus was observed with increasing percentages of the PAL filler in the polyethylene matrix. On the other hand, analysis of thermal transport properties revealed a marked enhancement in thermal conductivity as the filler percentage was increased. Given the substantial increase in thermal conductivity coupled with a negligible decrease in modulus, LDPE-PAL with 10 wt% filler loading was selected for an extrusion process to obtain a filament with a suitable shape and size for additive manufacturing process.