Burcu Saner Okan

The increasing energy demand of urban infrastructure and the intensification of the Urban Heat Island effect necessitate the development of multifunctional cement-based material systems with simultaneous enhanced thermal insulation and mechanical effectiveness. Driven by this, the present study reports the development of a strategy which relies on doping cement pastes and mortars with graphene oxides (GO) of targeted structural and chemical defects, for endowment of thermal insulation without loss of mechanical performance. GO was synthesized through an oxidation process and incorporated into Portland-limestone and pozzolanic cement matrices at various concentrations. The resulting nanomodified cements were tested under X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy, mechanically in bending and compression and their thermal transport potential was assessed as well. Mechanical characterization demonstrated that GO presence improved the load-bearing capacity, with recorded strength increases reaching 3.7% for flexural strength and 8.6% for compressive strength. Most importantly, substantial reductions in thermal conductivity were noted in nano-modified cement pastes, reaching remarkable drops up to 67.9% when structurally defected GO flakes, originating from oxidized graphite, were utilized. Corresponding drops by 31.5% were documented in the case where chemically defected flakes from graphene nanoplatelets were used. The thermal attenuation is attributed to enhanced phonon scattering induced by the engineered defects, the increased interfacial thermal resistance (Kapitza resistance), the vibrational mismatch, and the enhanced tortuosity of the heat-conduction pathways within the cementitious matrix. The results highlight defect-engineered GO as a nanoscale modificator for cement, that can simultaneously offer thermal conduction suppression and mechanical performance enhancement.

As the automotive sector seeks lower‐carbon alternatives to glass fiber–reinforced polymers, biomass‐derived carbons are increasingly explored as sustainable reinforcements. However, biomass precursors are often treated as generic carbon sources, leaving the relationships among waste origin, carbon structure, composite performance, and environmental impact insufficiently understood. Here, lemon peel, orange peel, walnut shell, and pistachio shell were converted under identical thermal–chemical conditions into defect‐rich nano‐carbon plates, enabling a controlled comparison of precursor‐dependent structure–property–environmental relationships. Citrus‐derived materials exhibited more wrinkled and oxygen‐rich morphologies, whereas nutshell‐derived materials, particularly those from pistachio shell, showed more carbon‐rich surfaces and higher C/O ratios. At 1 wt.% loading, the nano‐carbon plates increased PP tensile strength by up to approximately 34% while largely preserving ductility. In MAPP‐compatibilized composites containing 40 wt.% flax fiber, the pistachio‐derived system achieved tensile and flexural strengths of approximately 52 and 75 MPa, respectively. Cradle‐to‐gate LCA revealed strong feedstock‐ and scale‐dependent differences. The pistachio‐derived hybrid showed a GWP of 2.65 kg CO ₂ eq with virgin PP, slightly below the 30GF‐PP benchmark of 2.78 kg CO ₂ eq, while recycled PP reduced the GWP to 1.61 kg CO ₂ eq, corresponding to a 42.1% reduction. This study establishes a feedstock‐sensitive upcycling strategy for realistic circular composite design.

Achieving uniform dispersion and strong interfacial coupling between hexagonal boron nitride (h‐BN) and thermoplastic polyurethane (TPU) remains a key challenge for enhancing composite performance. In this study, low‐loading h‐BN/TPU composites were fabricated using a thermokinetic shear‐mixing process, which facilitated efficient platelet breakup and improved filler–matrix interactions. This scalable approach led to simultaneous improvements across thermal conductivity, mechanical stiffness, and crystallization behavior. The in‐plane thermal conductivity increased from 0.233 to 0.250 W m ⁻¹ K ⁻¹ at 3 wt.% h‐BN. Notably, the incorporation of h‐BN significantly enhanced the mechanical performance, with the tensile flexural moduli increasing by up to 83.6% and by 35%, respectively, indicating efficient load transfer within the matrix. Furthermore, h‐BN acted as an effective nucleating agent, substantially elevating the crystallization temperature. The resulting modulus values at 2.0–3.0 wt.% loading align with industry specifications for automotive‐grade flexible components, such as sealing elements and protective boots, while maintaining essential elongation capability. A complementary life‐cycle analysis (LCA) confirmed the environmental viability of these composites, with global warming potential (GWP) values remaining below 1.0 kg CO ₂ ‐eq per batch. These findings position low‐loading h‐BN/TPU composites as sustainable, high‐performance candidates for lightweight automotive applications.

Efficient heat dissipation in carbon fiber reinforced polyetheretherketone (CF/PEEK) thermoplastic composites remains limited due to the inherently low thermal conductivity of PEEK and restricted heat transfer across the laminate thickness, constraining their use in demanding aerospace environments. To address these limitations, this study presents a scalable composite manufacturing strategy based on the integration of the continuously extruded, thermally conductive hexagonal boron nitride (hBN)–filled PEEK films (30 wt.%) with film-stacked carbon fiber laminates. In addition, localized electrospray deposition of hBN onto carbon fiber fabrics is employed to promote interfacial thermal bridging and enhance through-thickness heat transport. The combined processing route encompassing continuous film manufacturing and prepreg-compatible composite fabrication results in simultaneously improving in-plane and through-plane thermal transport pathways. The resulting hierarchical hBN/CF/PEEK laminates exhibit a 21.88% increase in in-plane thermal conductivity (κ _∥ = 5.914 W·m ⁻¹ K ⁻¹ ) compared to conventional CF/PEEK composites, while electrospray-modified laminates demonstrate a 369.13% enhancement in through-plane thermal conductivity (κ _⊥ ). The incorporation of hBN-filled films also leads to a significant increase in laminate stiffness, with Young’s modulus improving by 54.25%, accompanied by predictable changes in tensile failure mechanisms. By combining continuous extrusion of thermally conductive PEEK films with scalable composite consolidation, this work establishes an industry-relevant manufacturing route for high-temperature thermoplastic composites, offering improved thermal management and mechanical performance for advanced structural applications.

The automotive industry's pursuit of lightweight, high‐performance, and sustainable materials has driven interest in natural fiber‐reinforced thermoplastics. However, challenges such as moisture sensitivity, lower strength, and fiber‐matrix compatibility hinder their widespread adoption. To address these constraints, this study developed sustainable compound formulations incorporating recycled waste components and natural fibers as alternatives to injection‐molded composites reinforced with long glass fibers (LGF) for structural applications in the automotive industry. The newly developed compound comprised PP reinforced by 40 wt% alkaline treated flax fiber (FF), 1 wt% waste tire‐derived graphene nanoplatelets (GNP), and 3 wt% compatibilizer, resulting in significant improvements in flexural modulus and strength, surpassing both neat homopolymer PP (homoPP) and recycled PP (rePP) by 202% and 92.5%, and 161.5% and 54.7%, respectively. To assess their viability, mechanical, thermal, and rheological properties were compared with commercial counterparts used in serial production. Furthermore, a comparative life cycle assessment evaluated the carbon footprint of different matrix types, revealing that the rePP‐based formulation reduced CO ₂ emissions by 50% compared to LGF/homoPP while achieving a 7.2% weight reduction. This study successfully demonstrates the potential of integrating natural fibers and waste‐derived reinforcements into PP composites, offering a lightweight, high‐performance, and environmentally friendly alternative for automotive applications. Highlights: Sustainable PP composites developed as alternatives to glass fiber materials Flax fibers and upcycled GNP utilized for lightweight composite fabrication Flexural modulus and strength significantly improved in PP composites. Life Cycle Assessment performed for developed and commercial composites 50% CO ₂ emission reduction achieved using recycled PP as a matrix in composites.