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.

The present paper focuses on the effect of carbon nanotubes (CNTs) on the rheological behavior of polyethylene/polypropylene (PE/PP) blends to improve PE/PP mixtures for industrial applications. In our research, 40 wt% HDPE-60 wt% PP blends were produced by extrusion, and 0.59%, 1.18%, and 2.35% multiwalled carbon nanotubes (MWCNTs) were added. Oscillation rheometry was used to study the HDPE-PP-MWCNT nanocomposites and the unfilled polymers at temperatures of 210, 220, 230, 240, and 250 °C in the angular frequency range of 0.05–628.32 rad/s, with 5% deformation. It was demonstrated that in the presence of CNTs, both the complex viscosity and modulus values increase above the percolation threshold. Additionally, it was observed that the crossover modulus (Gx) for all mixtures decreases with increasing temperature. In addition, at 1.18% CNT content, a second crossover appears at all temperatures, and its value increases with temperature.

The present study investigates the effect of repeated mechanical recycling on the phase composition and viscoelastic behavior of injection-molded poly(ethylene terephthalate) (PET). Virgin PET and materials subjected to one, two, and three consecutive recycling cycles were characterized using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The crystalline fraction (CRF), mobile amorphous fraction (MAF), and rigid amorphous fraction (RAF) were determined using a three-phase model based on DSC measurements. Recycling modified both the crystalline and amorphous phase composition of PET, producing a moderate increase in mean crystallinity and non-monotonic changes in the amorphous fractions. DMA measurements showed an overall tendency toward higher mean storage modulus after repeated recycling, although specimen-to-specimen scatter was considerable, whereas the glass-transition temperatures changed only slightly. Normalized modulus-plane trajectories indicated differences in relaxation behavior but, because they were obtained from single-frequency temperature sweeps, were not interpreted as conventional frequency-domain Cole–Cole spectra. The combined DSC and DMA results reveal associations between phase composition and the viscoelastic response of mechanically recycled PET while also identifying important experimental limitations.

3D printing has grown rapidly and is now widely used in many industries, including the automotive sector. Most 3D printing filaments are made from virgin PLA (polylactic acid); however, at the same time, the packaging industry produces large amounts of PLA waste, which is often not recycled properly. Turning this waste into good-quality 3D printing filament could be an eco-friendly alternative to traditional materials and support sustainability in the automotive supply chain. This research investigates whether the original PLA packaging material can be used for 3D printing at all by testing its printability and mechanical properties compared to commercial PLA filaments. Two types of original packaging PLA were chosen and processed into 3D printing filaments, which were then tested. The results show that packaging PLA filaments have mechanical properties similar to or even better than commercial PLA filaments, proving that they can be a useful material for 3D printing.