This study investigates the hydrogen permeability of injection-molded polyamide 6 (PA6) nanocomposites reinforced with organo-modified montmorillonite (OMMT) at varying concentrations (1, 2.5, 5, and 10 wt. %) for potential use as Type IV composite-overwrapped pressure vessel (COPV) liners. While previous work examined their mechanical properties, this study focuses on their crystallinity, morphology, and gas barrier performance. The precise inorganic content was determined using thermal gravimetry analysis (TGA), while differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM) were used to characterize the structural and morphological changes induced by varying filler content. The results showed that generally higher OMMT concentrations promoted γ-phase formation but also led to increased agglomeration and reduced crystallinity. The PA6/OMMT-1 wt. % sample stood out with higher crystallinity, well-dispersed clay, and low hydrogen permeability. In contrast, the PA6/OMMT-2.5 and -5 wt. % samples showed increased permeability, which corresponded to WAXD and SEM evidence of agglomeration and DSC results indicating a lower degree of crystallinity. PA6/OMMT-10 wt. % showed the most-reduced hydrogen permeability compared to all other samples. This improvement, however, is attributed to a tortuous path effect created by the high filler loading rather than optimal crystallinity or dispersion. SEM images revealed significant OMMT agglomeration, and DSC analysis confirmed reduced crystallinity, indicating that despite the excellent barrier performance, the compromised microstructure may negatively impact mechanical reliability, showing PA6/OMMT-1 wt. % to be the most balanced candidate combining both mechanical integrity and hydrogen impermeability for Type IV COPV liners.

Separate collection of household bio-waste became mandatory across the European Union in 2024, increasing the use of biodegradable paper and plastic liners for kitchen waste. While these materials improve source-separation and hygiene, their behavior during Anaerobic Digestion (AD) remains insufficiently understood and may affect plant performance and digestate quality. This study evaluated five commercially available collection bags – three paper-based and two biodegradable plastic types – under mesophilic batch AD conditions. Paper bags increased methane and biogas yields by approximately 5–20 %, while biodegradable plastics resulted in similar or slightly reduced yields compared to controls. Neither material showed substantial structural degradation, but paper provided additional substrate and surface area, supporting modest efficiency gains. In contrast, persistent plastic fragments in the digestate may limit its agricultural use under strict EU fertilizer regulations, leading to higher post-treatment costs. These findings highlight that paper liners are more compatible with AD-based waste management systems, informing municipalities, policymakers, and operators in selecting collection tools that optimize resource recovery and regulatory compliance.