The present paper investigates the suitability of a vitrimeric epoxy resin for processing in the wet filament winding (WFW) process to manufacture fiber‐reinforced polymers (FRP). Comprehensive material characterization of a commercially available epoxy and vitrimeric resin based on disulfide exchange is carried out, and the processing in WFW is evaluated by analyzing thermomechanical, rheological, thermochemical properties, and chemical shrinkage. The direct comparison of a vitrimer and an established epoxy resin permits an indication of the processability and necessary adjustments in WFW. Based on the implications of modeling, we demonstrate the processing of the vitrimeric resin in the WFW process by increasing the resin bath temperatures. The vitrimer's and conventional resin's elastic modulus development and compression behavior were similar, highlighting the vitrimeric resin's potential. Further, the results confirm that established characterization and modeling routines can be transferred to vitrimeric resins and, therefore, path the way toward advanced process simulation of vitrimeric resin's processing. For this, the present publication gives essential advice for setting up testing schedules for characterizing epoxy vitrimers' processing behavior and their appropriate modeling. The present work underlines the potential of applying commercially available dynamic hardeners to manufacture recyclable and malleable FRP in established processes.Highlights: Material characterization and modeling of wet filament winding process. Wet filament winding of epoxy vitrimers. Thermomechanical and chemical shrinkage characterization of epoxy vitrimers. Rheological and kinetic modeling of epoxy vitrimer.

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.

Fibre-reinforced composites are facing new challenges in the context particular in sustainability and recyclability. Vitrimers could be useful as new matrices to support the increase in sustainability. Due to their high strength, which is comparable to that of thermosets often used in composites, and their covalent adaptive networks, which make them reshapeable for scaled-up manufacturing and recycling purposes, they are very useful. Orthogonal cutting is used for precise reshaping and functional integration into carbon fibre reinforced plastics. Vitrimers could improve processing results at the cutting edge as well as surface quality thanks to their self-healing properties compared to brittle matrices, as well as enabling the recycling of formed chips and scrap. This study showcases the manufacturing of a carbon fibre-reinforced vitrimer using 4-aminophenyl disulfide as a hardener, with vacuum-assisted resin infusion. The temperature of chip formation and the cutting parameters are then shown for different fibre orientations, cutting widths and speeds. The observed cutting forces are lower (less than 140 N) and more irregular for fibre orientations 45°/135°, increasing with cutting depth, and fluctuating periodically during machining. Despite varying cutting speeds, the forces remain relatively constant in range between 85 N and 175 N for 0°/90° fibre orientation and 50 N and 120 N for 45°/135° fibre orientation, with no significant tool wear observed and lower-damage depth and overhanging fibres observed for 0°/90° fibre orientation. Damage observation of the cutting tool shows promising results, with lower abrasion observed compared to thermoset matrices. Microscopic images of the broached surface also show good quality, which could be improved by self-healing of the matrix at higher temperatures. Temperature measurements of chip formation using a high-speed camera show a high temperature gradient as cutting speeds increase, but the temperature only ever exceeds 180 °C at cutting speeds of 150 m/min, ensuring reprocessability since this is below the degradation temperature. Therefore, orthogonal cutting of vitrimers can impact sustainable composite processing.

The deinking of plastic packaging waste offers the potential of decreasing contamination and thus increasing the overall quality of recycled plastics, enabling their use in more demanding applications. The removal of printing inks from the usually heavily printed flexible polyethylene (PE) plastic films yields transparent flakes that generally allow the recycling into materials with better mechanical properties as well as lower odor and optical defects. However, for flexible PE packaging waste, the deinking is not yet implemented on an industrial scale and there is currently no objective methodology to evaluate the deinking effect on those inhomogeneous flakes. In this study, a novel approach for the objective assessment of the ink removal on flexible post-consumer waste (PCW) is proposed. Via an image-based analysis, the transparency of the flakes is transformed into the 8-bit grey scale, and the calculation of statistical characteristics from these grey value distributions allows to quantifiably compare the deinking efficiency of several experiments. Using this analysis method allows to investigate the general behavior of contaminated PCW materials in deinking and to identify the most effective parameters for ink removal.

To efficiently reuse endless fibre-reinforced composites after their life cycle, the recovery of endless fibres including matrix material with subsequent reprocessing in their original state is desirable. Thanks to their covalent adaptive networks, vitrimers offer ideal properties for enabling new repair and circular strategies for composites. In order to evaluate the detachability—meaning the separation of single laminate layers—and recycling potential for continuous fibre reinforcement, process routes and quality parameters must be established. In this study, the double cantilever beam test is used to test the adhesion based on the detachment of continuous fibre layers, and the interlaminare fracture toughness of mode I (G_IC) is measured as a parameter for the required energy for detachment. It was shown that G_IC increases above the vitrimer transition temperature and is higher than for reference specimens with an epoxy matrix. Surface roughness is measured to determine the mechanical and thermal degradation of the chemical network structure and additionally shows fibre cracking and defects in fibre–matrix interfaces. This allows the recycling process to be evaluated up to the production of a second generation, with the aim of identifying the recycling potential of the vitrimer matrix and implementing it for industrial processes. An efficient recycling strategy of the continuous fibre-reinforced vitrimers was thus demonstrated by hot pressing at 190 °C for 45 min, giving vitrimer samples a second life.

Ecological driven sustainability of plastic materials encounters a major challenge in eco-efficient mechanical recycling falling short of meeting the required quality and quantities of post-consumer-recyclates (PCR) in sensitive applications areas demanded by regulatory authorities. Remaining toxicological concerning residues of contaminants after mechanical recycling restrict the use in sensitive application areas. Addressing the integration of PCR into high demanding applications, such as food contact materials, this work investigates a novel technology for PCR product use by an innovative migration barrier development pathway of Si-based plasma enhanced chemical vapour deposition (PECVD) coatings on pre-contaminated polypropylene (PP) model PCR cups compliant with applicable regulatory frameworks including European Food Safety Authority (EFSA) authorization requirements. As a starting point for migration barrier development optimized oxygen transmission rate (OTR) barrier coatings for PCR cups were reproduced and transferred on virgin and model PCR PP-cups. The coating procedure consisted out of a pretreatment, applied organic adhesion interlayer SiOCH and inorganic functional barrier layer SiOx, where the functionality was related to the applied SiOx layer based on the barrier efficiency. Therefore, SiOx was varied in the migration barrier development to find a suitable process window and efficiently correlate the effects of process parameters on OTR before and after migration testing, mass loss of simulant and the reduction of migration of eight introduced contaminants in the model PCR cup using GC/MS. This work advanced the understanding of PECVD as migrations barriers under regulatory frameworks and reduced PCR matrix complexity in the analysis during development using model PCR cups.