In this work, the influence of a modification and fillers on the dimensional stability and warpage of semi‐crystalline polypropylene compounds in screw‐based Large Area Additive Manufacturing is investigated by material characterization and experimental testing. Polypropylene is modified by blending an amorphous polyolefin‐copolymer as well as the addition of three different fillers talc, glass fibers, and hollow glass beads, resulting in eight investigated compounds. A material characterization using Differential Scanning Calorimetry, Thermogravimetric Analysis, thermal conductivity measurements, and pvT‐measurements is carried out. Experimental investigations regarding dimensional stability and warpage deformation during processing are performed. By increasing the crystallization temperature and thermal conductivity from 112.3°C and 0.208 W/(m°C) to 127°C and 0.232 W/(m°C) through the use of a modification and talc, a better dimensional stability during processing is reached. Furthermore, both the modification of the base material and the introduction of talc or glass fibers lead to a significant reduction in the decrease in specific volume during cooling, as determined by pvT‐measurements, thus reducing warpage. The experimentally determined warpage deformation could be reduced by 69% when using 10 wt. % talc‐filler and by 78% when using 10 wt. % glass fibers, compared to the unmodified and unfilled base polypropylene.

The production of fibre-reinforced composites for use in applications such as type-4 pressure vessels for hydrogen storage is achieved through the use of a thermoset matrix. However, the recycling of thermosets presents a significant challenge due to the lack of established recycling methods. Epoxy-based vitrimers show thermoset characteristics during the manufacturing and utilisation phases but exhibit thermoplastic behaviour at elevated temperatures of 190 °C. This study investigates the industrial-scale production of carbon fibre reinforced vitrimers via a wet filament winding, as exemplified by a type-4 pressure vessel demonstrator. Processing conditions of industrial processes have yet to be applied to vitrimers; therefore, two vitrimer formulations are compared to a conventional epoxy thermoset. The processability and resulting composite quality of wound composites using these materials as matrices are compared. The mechanical properties of the composites are compared using an interlaminar shear strength test, demonstrating that the vitrimeric matrices exhibit 19.8% (23 °C) and 49.2% (140 °C) improved interlaminar strength. Consequently, the epoxy-based vitrimers investigated in this study can be employed as a direct replacement for the thermoset matrix in industrial-scale applications, with the potential for recycling the composite. To increase composite qualities, the winding process must be adapted for vitrimers, since a pore free composite could not be achieved.

Selective, nanometer-thin organosilica layers created by plasma-enhanced chemical vapor deposition (PECVD) exhibit selective gas permeation behavior. Despite their promising pure gas performance, published data with regard to mixed gas behavior are still severely lacking. This study endeavors to close this gap by investigating the pure and mixed gas behavior depending on temperatures from 0 °C to 60 °C for four gases (helium, methane, carbon dioxide, and nitrogen) and water vapor. For the two permanent gases, helium and methane, the studied organosilica membrane shows a substantial increase in selectivity from αHe/CH₄ = 9 at 0 °C to αHe/CH₄ = 40 at 60 °C for pure as well as mixed gases with helium permeance of up to 300 GPU. In contrast, a condensable gas such as CO₂ leads to a decrease in selectivity and an increase in permeance compared to its pure gas performance. When water vapor is present in the feed gas, the organosilica membrane shows even stronger deviations from pure gas behavior with a permeance loss of about 60 % accompanied by an increase in ideal selectivity αHe/CO₂ from 8 to 13. All in all, the studied organosilica membrane shows very promising results for mixed gases. Especially for elevated temperatures, there is a high potential for separation by size exclusion.

In light of climate change, fiber-reinforced plastics (FRP) are becoming increasingly important due to their lightweight construction potential. This benefit is additionally expanded on with the low cycle times, scrap rates and material costs of Sheet Moulding Compounds (SMC), making it the most often used material on the FRP market. While extensive studies regarding the recycling of SMC with unsaturated polyester-based matrices (UP-SMC) have been conducted in the past, this is not the case for vinylester-based SMC (VE-SMC). In this research, VE-SMC components were subject to a particle-recycling approach. Recyclate in the form of VE-SMC regrind was used to substitute SMC matrices during the compounding process. The dependence of the mechanical properties and failure behavior of VE-SMC containing regrind was investigated by means of microscopic and mechanical test methods for varying mass proportions of SMC regrind. Due to the addition of SMC regrind, a decreased fiber/matrix adhesion was observed. Furthermore, an increase in pore formation was observed with an increasing proportion of SMC regrind. The flexural modulus increased by 20% with a low percentage of regrind (ω_rSMC = 10 wt.%) in comparison to virgin SMC. In contrast, the tensile properties decrease (up to 30%) with the addition of SMC regrind independent of the investigated proportions of SMC regrind.

The recycling of plastics collected from household waste to produce post-consumer recycled (PCR) materials is a critical step of sustainable waste management. However, the processing of PCR materials presents unique challenges, particularly in the context of seasonal input stream fluctuations and resulting PCR material composition variations. Within this paper, the influence of batch-to-batch fluctuations on the processing stability and product properties of high-density polyethylene (HDPE) PCR from the German municipal waste system is analysed. It examines how variations in batch composition affect key parameters such as processing data (injection pressure, torque), mechanical properties (tensile strength, E-modulus, impact strength), and product quality (gel formation, part dimensions, part weight). Therefore, six consecutive household HDPE PCR material batches are analysed regarding their composition, contaminations, and rheological characteristics through ashing, differential scanning calorimetry, high-temperature gel permeation chromatography, and high-pressure capillary rheometry. The batches are then processed using blown- and cast-film extrusion as well as injection moulding, and the resulting process stability and product quality are analysed. The results show a strong correlation between thermal properties, such as crystallisation enthalpy, molecular weight, polypropylene (PP) content, varying batch viscosities, and changes in processing data as well as the resulting product properties.