Structure-processing-properties relationships in graphene-nylon 6 nanocomposites : a study of masterbatch dilution
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Date
2025-07-08
Authors
Μπιτινή, Χριστιάννα-Αικατερίνη
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Abstract
This thesis explores the production and analysis of polyamide 6 (PA6) nanocomposites reinforced with reduced graphene oxide (rGO), emphasizing how the processing parameters influence the final material properties. The nanocomposites were produced via the masterbatch dilution process, an industry-relevant method that allows the precise addition of nanofillers into thermoplastics. Two processing strategies were used, a two-step process involving pre-mixing and twin-screw compounding, and a one-step process relying on direct dilution during injection moulding, using either a long-screw or a short-screw configuration. These processing routes were evaluated for their influence on the dispersion quality of rGO and the resulting composite’s performance. To evaluate the effective incorporation and distribution of rGO within the PA6 matrix, the materials were characterized through an extensive set of techniques. Differential Scanning Calorimetry (DSC) was used to examine thermal transitions and crystallinity, while mechanical testing was used to evaluate stiffness, strength, and ductility. X-Ray Diffraction (XRD) was performed to examine the crystalline structure and phase composition of the materials. These techniques provided insight into how both rGO concentration and processing method influence the internal structure and physical properties of the nanocomposites. rGO incorporation enhanced multiple performance aspects. The addition of rGO, particularly in pre-mixed composites, improved the Young’s modulus, and the thermal analysis revealed that the primary transition temperatures of PA6 stayed stable, with only minor shifts in crystallinity depending on rGO content. XRD confirmed the dominance of α-phase crystalline structure, with minor intensity changes. The results indicated that the best route for masterbatch dilution is the two-stage process.
Furthermore, the study focused on the investigation of surface and environmental performance of the materials through a series of ad-hoc experiments, targeted to assess possible application of the PA6-rGO nanocomposites for the development of automotive components, such as tanks for fuel and AdBlue. For instance, contact angle measurements were carried out to evaluate surface wettability in the presence of AdBlue. Moreover, ethanol absorption tests were performed to simulate exposure to biofuels, demonstrating the resistance of the nanocomposites to chemical uptake and swelling. Accelerated UV aging experiments were conducted to investigate the durability of the materials against photodegradation, simulating long-term outdoor or under-the-hood exposure. The above experiments demonstrated the reduced wettability of the nanocomposites to AdBlue, reduced ethanol uptake, and greater resistance to UV-induced degradation compared to pristine PA6. Notably, the ethanol absorption behavior displayed non-Fickian diffusion characteristics. Overall, the findings highlight that both the concentration of rGO and the quality of dispersion, which is
significantly affected by the processing technique, are crucial in defining the performance of the composites. These results indicate that rGO/PA6 nanocomposites are appropriate for automotive and industrial applications that require enhanced thermal stability, chemical resistance, and environmental durability. Moreover, the effectiveness of the masterbatch dilution method is highlighted as a scalable and controllable technique for producing advanced nanocomposites.
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Keywords
Polyamide 6, Graphene, Reduced graphene oxide, Nanocomposites, Masterbatch dilution method, Ethanol absorption, Non-fickian sorption, UV aging, Contact angle, Automotive materials