Assessing the environmental impact of cryogenic treatment in recycling scenarios for PBT-GF30 components

Abstract

Glass-Fiber-Reinforced-Polymers (GFRP) have a considerable environmental impact. For companies that produce automotive products, this can be an issue, due to the current need to comply with EU sustainable goals. The environmental impact of the GFRP, that includes PBT-GF30, increases when products incorporate other material, such as metallic screws. When the products come out defective from the manufacturing, the complete segregation between metal and plastic is complex. Therefore, the product EoL is usually the landfill and the lack of their recyclability raised an environmental concern. To overcome this environmental issue, this study pointed out Cryogenic Treatment (CT) as a technique to fragilize the GFRP, improving the recycling process in two ways: materials segregation and decreased energy for plastic's shredding. To conduct the analysis, PBT-GF30 samples, with and without screws, were subjected to CT and impact tests and afterwards a mechanical characterization was performed, confirming the variation of tensile strength. To complement the study, LCA and LCC was conducted for three scenarios of disposal of the defective parts – landfill; mechanical recycling; and CT before mechanical recycling, in order to characterize the environmental impact of the proposed solution compared to the current one, landfill. Results highlight that CT and impact lowered the PBT-GF30 stress at break by 30 %, requiring less energy by the same amount to break the material in the shredding process. The analysis identified the landfill scenario (baseline) as having the highest environmental impact, primarily due to the absence of material recovery, which increases the demand for raw materials, increasing extraction-related impacts. In contrast, recycling methods significantly reduced these burdens. CT before mechanical recycling, for instance, demonstrated a potential 30 % reduction in environmental impacts by reintegrating recycled materials into production processes, highlighting its potential to enhance sustainability. However, the high cost associated with liquid nitrogen production could be a limitation. Nonetheless, CT before mechanical recycling offers approximately 30 % lower costs than the baseline when viewed through a circular economy perspective, presenting a balanced approach to improving environmental and economic outcomes.