The transition to circular polymer manufacturing requires improved understanding of how recycled feedstock composition influences manufacturing energy demand and final material performance. While recycled fibre-reinforced thermoplastic composites have attracted increasing interest, the connected effects of material composition and processing conditions on specific energy consumption and mechanical properties remain insufficiently quantified. This study presents a systematic correlation-based analysis of post-industrial glass fibre-reinforced polypropylene (GFPP)-reinforced recycled polypropylene (rPP) composites, linking material composition, extrusion and injection moulding parameters, specific energy consumption, and tensile properties. The results show that increasing rPP content increases specific energy consumption by approximately 10%–15%, whereas higher GFPP and additive contents reduce energy demand by up to 12%. Among the processing parameters, higher extruder throughput improves machine efficiency and lowers energy consumption (up to 8%), while increased screw speed increases energy demand (approximately 9%). Tensile strength exhibits a positive correlation with GFPP content and extruder throughput, but decreases with increasing rPP content. These findings demonstrate the trade-offs between material circularity, energy efficiency, and mechanical performance. The novelty of this work lies in the integrated quantitative assessment of material composition, processing conditions, manufacturing energy consumption, and tensile behaviour within recycled fibre-reinforced polypropylene systems. The presented correlations provide practical guidance for optimising composite formulations and processing conditions to support energy-efficient, high-performance, and circular polymer manufacturing.
The present study examined the effects of various reinforcements, such as nano-powder, silica, eggshell and multi-walled carbon nanotubes, on the mechanical properties of friction stir-welded polystyrene and acrylonitrile–butadiene–styrene plates under different process parameters. Welding experiments were performed at different tool rotational speeds (TRSs) of 800, 900 and 1100 rpm, with traverse speeds of 9, 18 and 27 mm/min, respectively. A pinless tool was used to pack the reinforcement particles into the groove, and a cylindrical H13 steel tool was used to join the base materials. The findings indicated that the mechanical characteristics of the welded joints were significantly affected by the different types of reinforcement and process parameters. The maximum tensile strength of 22.41 MPa and an elongation of 3.81 were achieved at a tool traverse speed (TTS) of 18 mm/min and a TRS of 900 rpm using nano eggshell powder reinforcement, suggesting improved interfacial bonding and particle distribution. Conversely, the highest microhardness was recorded at a TTS of 27 mm/min and a TRS of 900 rpm with silica nano-powder reinforcement, owing to the enhanced resistance to localized deformation and improved load transfer capability.
Polyurethane-based composites (PUCs) are promising materials for stretch-forming dies used in aircraft skin components; however, their limited load-bearing capacity and insufficient wear resistance under severe conditions remain major challenges. In this work, graphite powder (GP) was incorporated into a polyurethane matrix to enhance its compressive and tribological performance. PUCs with different GP contents were fabricated by room temperature casting. Static compression tests, dynamic compression experiments using a split Hopkinson pressure bar, and wear tests under various normal loads were systematically performed. The results demonstrate that both elastic modulus and compressive strength first increase and then decrease with increasing GP content. When the GP content reached 5%, the composite exhibited the highest static compressive strength of 141.41 MPa, representing a significant improvement compared with the GP-free composite. Under dynamic loading, the composite containing 5% GP achieved the maximum dynamic compressive stress, which was 635.99 MPa at an impact pressure of 0.2 MPa. Moreover, composites with higher GP content exhibited markedly enhanced wear resistance under elevated normal loads. Scanning electron microscopy observations confirmed that GP promoted the formation of a stable lubricating transfer film, leading to a transition from severe adhesive wear to mild wear behavior.
To assess the feasibility of using bamboo-plastic composites in electrical insulation applications, the effect of fly ash-a type of highly productive coal power solid waste-on the in-service performance of bamboo-plastic composites for insulation (hereafter referred to as bamboo-plastic insulating materials) was investigated. The evaluation was based on four standard criteria for solid insulation materials: water repellency, mechanical properties, electrical properties, and voltage resistance. The results showed that with increasing fly ash content, all four properties initially improved and then declined. The maximum reductions in water absorption and the dielectric loss factor were 20.7% and 35.8%, respectively, while the maximum increases in contact angle, tensile strength, flexural strength, insulation resistance, surface flashover voltage, and breakdown voltage were 25.0%, 21.3%, 14.4%, 36.1%, 35.9%, and 7.5%, respectively. Following the breakdown, the microstructure of the bamboo-plastic insulating materials, irrespective of fly ash content, exhibited continuous conductive channels and irregularly distributed pitting.
The study reports the preparation and characterisation of non-apparel grade wool–natural rubber (NR) composites. Non apparel textile grade wool obtained from Malpura sheep (highly coarse) and Chokla sheep (medium coarse) were converted in to hand woven fabric in a conventional handloom. Both the fabrics were milled, scoured and coated with different natural rubber latex concentrations through padding method. The latex-coated wool fabrics were then vulcanised at higher temperature and pressure to prepare wool–NR composites. The physical and mechanical properties of the developed wool fabrics and wool–NR composites such as fibre loading, tensile strength, elongation, Young's modulus, tear strength, porosity, hardness, abrasion resistance, moisture content, static and dynamic frication and water diffusion were analysed. The composites were further characterised with Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The aging properties of composites due to accelerated thermal, UV exposure and soil degradation was also performed. Upon comparing the physico-mechanical properties, it is observed that the DRC (Dry Rubber Content) was found to be the governing factor in determining the mechanical properties of the composites. While coating with same natural rubber latex concentration, the mechanical properties of the medium coarse wool–NR composite was found to be higher as compared to the highly coarse wool–NR composite. Prolonged exposure to high temperature and UV radiation caused a significant reduction in mechanical properties of the composites. Upon accelerated soil burial for 120 days, the pristine wool fabric was found to be fully decomposed meanwhile, the composites with high rubber content exhibited less degradation.
