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Molded pulp packaging is rapidly growing as a sustainable packaging solution, but cost remains one of the biggest challenges. This study systematically investigates the potential use of mineral fillers as a cost-reduction strategy for molded pulp, using a design-of-experiments (DOE)-based approach. Laboratory-scale samples were produced with two ground calcium carbonate (GCC) fillers of different particle sizes at increasing dosages, and pore structure, mechanical properties, and dewatering/drying efficiency across stages of the molded-pulp process were assessed. With increasing filler dosage, mechanical properties decreased in three steps: slow initially, a steep mid-stage drop, then a slower final decline. The pore structure results correlated with this three-step change. The optimal filler-dosage range was determined from this three-step behavior and defined as the dosage corresponding to 80% of the maximum mechanical properties. GCC fillers improved the dewatering capability of the pulp suspension; however, this did not translate into improved dewatering efficiency at later stages. Future research is suggested to enable the successful application of mineral fillers in molded pulp products.

Due to growing restrictions on the use of halogenated flame retardant compounds, there is great research interest in the development of fillers that do not emit toxic compounds during thermal decomposition. Polymeric composite materials with reduced flammability are increasingly in demand. Here, we demonstrate that unmodified graphene and carbon nanotubes as well as basalt fibers or flakes can act as effective flame retardants in polymer composites. We also investigate the effects of mixtures of these carbon and mineral fillers on the thermal, mechanical, and rheological properties of EPDM rubber composites. The thermal properties of the EPDM vulcanizates were analyzed using the thermogravimetric method. Flammability was determined by pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry.

We studied the effects of silicon carbide (SiC) and SiC hybrid systems with different conventional fillers (silica, carbon black, graphene, hydrotalcite, halloysite) on the rheometric measurements, crosslink density, mechanical performance, aging stability, morphology, thermal behaviour, and flammability of ethylene-propylene-diene (EPDM) rubber composites. The hybrid filler systems showed technically promising synergetic effects on the performance of the EPDM composites. A pronounced reinforcing effect in EPDM composites filled with hybrid SiC filler systems was noted. Tensile strength increased in the systems with carbon black, silica, and graphene nanoplatelets, by 21%, 37%, and 68%, respectively, compared to the neat EPDM. Dynamic-mechanical analysis (DMA) revealed a shift of the glass transition temperature (Tg) of EPDM composites towards higher values following the incorporation of hybrid SiC fillers, indicating that the mobility of the macromolecule chains was restricted by the presence of filler particles. Importantly, the application of SiC as a filler in EPDM rubber composites contributed to a considerable reduction in flammability, as demonstrated by microscale combustion calorimetry (MCC). The most promising results were obtained for HAL/SiC and LDH/SiC hybrid systems, which produced final composites with high flame retardancy and good mechanical performance. The study highlights the significant potential of SiC and SiC hybrid systems as effective fillers improving the properties of elastomer composites.

It is commonly known that mineral fillers significantly affect the asphalt mixture's performance. Superior flexible pavement performance can be ensured by gaining a deeper understanding of the function of filler. This research investigates the influence of three different fillers: granite dust, cement, and hydrated lime, at Australian asphalt mixtures. The testing program includes Marshall testing, moisture damage resistance, indirect tensile strength (ITS), and indirect tensile stiffness modulus (ITSM) tests of asphalt mixtures. Analysis of variance (ANOVA) was used to statistically assess the results obtained, besides damage analysis. The results indicate that using natural granite dust yields the highest resistance to moisture, while cement produces the highest stability, ITS, and ITSM. Unexpectedly, using hydrated lime filler decreases the stability/stiffness and moisture resistance of asphalt mixtures. ANOVA tests indicate that the type of filler affects ITS, TSR, and ITSM results (i.e., the p-value <0.05). The damage analysis shows that the design life of the asphalt mixture made with cement filler is higher than that of mixtures made with natural granite dust and hydrated lime fillers respectively. The findings indicate the important role of nontraditional fillers at the performance of Australian asphalt mixtures.

The property of asphalt mastic directly affects the service performance of asphalt mixtures and pavements. Previous studies have demonstrated that the interaction between asphalt binder and mineral fillers has a significant effect on the performance of asphalt mastics. However, the interaction hasn’t been characterized by direct tests. In this study, an adsorption–separation test of asphalt binder on surface of mineral fillers was conducted to separate the structure asphalt binder and free asphalt binder. Atomic force microscope (AFM) PeakForce QNM mode was used to characterize the morphology and mechanical property of asphalt binder at different distances to filler surface. Results show that the effected thickness of binder–filler interaction was around 1 μm. Within this specific thickness, the “bee” structure of asphalt surface disappears gradually, and the modulus increases significantly when the tested samples are closer to the aggregate surface.

For the first time, the kinetics of isothermal curing and thermal degradation of polyethylene glycol maleate (pEGM)–based systems and their composites with mineral fillers were investigated in the presence of a benzoyl peroxide/N,N-Dimethylaniline redox-initiating system. DSC analysis revealed that the curing process at 20 °C can be described by the modified Kamal autocatalytic model; the critical degree of conversion (αc) decreases with increasing content of the unsaturated polyester pEGM and in the presence of fillers. In particular, for unfilled systems, αc was 0.77 for pEGM45 and 0.60 for pEGM60. TGA results demonstrated that higher pEGM content and the incorporation of fillers lead to increased thermal stability and residual mass, along with a reduction in the maximum decomposition rate (dTGₘₐₓ). Calculations using the Kissinger–Akahira–Sunose and Friedman methods also confirmed an increase in the activation energy of thermal degradation (Ea): EKAS was 419 kJ/mol for pEGM45 and 470 kJ/mol for pEGM60, with the highest values observed for pEGM60 systems with fillers (496 kJ/mol for SiO2 and 514 kJ/mol for CaCO3). Rheological studies employing three-interval thixotropy tests revealed the onset of thixotropic behavior upon filler addition and an increase in structure recovery after deformation of up to 56%. These findings underscore the potential of pEGM-based systems for low-temperature curing and for the design of composite materials with improved thermal resistance.

The present work aims to enhance the use of agricultural byproducts for the production of bio-composites by melt extrusion. It is well known that in the production of such bio-composites, the weak point is the filler-matrix interface, for this reason the adhesion between a polylactic acid (PLA)/poly(butylene succinate)(PBSA) blend and rice and wheat bran platelets was enhanced by a treatment method applied on the fillers using a suitable beeswax. Moreover, the coupling action of beeswax and inorganic fillers (such as talc and calcium carbonate) were investigated to improve the thermo-mechanical properties of the final composites. Through rheological (MFI), morphological (SEM), thermal (TGA, DSC), mechanical (Tensile, Impact), thermomechanical (HDT) characterizations and the application of analytical models, the optimum among the tested formulations was then selected.

The global asphalt industry seeks sustainable alternatives to reduce its environmental footprint. This study investigates the potential of an industrial by-product, namely lime kiln dust (LKD) as an alternative mineral filler for asphalt mixtures, focusing on its impact on physico-chemical properties and overall mixture performances. Collaborative efforts involving university and industry laboratories were undertaken from sample preparation to performance testing and to investigate the potential of LKD-modified mixture. Through a comprehensive laboratory investigation involving mechanical tests (Marshall stability, indirect tensile strength, resilient modulus, dynamic creep, and Hamburg wheel tracking) and microstructural analysis (field emission scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray diffraction), LKD-modified mixtures demonstrated superior performance. The main quantitative results show that the AC14 + 2%LKD mixture exhibited a 27% increase in resilient modulus (5549 MPa vs. 4375 MPa) and a 58% higher Dynamic Stability (4167.94 vs. 2630.06 cycles/mm) compared to the standard AC14 + 2%OPC mixture. Furthermore, LKD mixtures showed enhanced moisture resistance, with the AC20 + 2%LKD mix achieving a tensile strength ratio of 1.21, indicating superior moisture damage resistance compared to conventional fillers. Critically, the AC14 + 2%LKD mixture demonstrated a 44% reduction in rut depth (2.51 mm vs. 4.50 mm) compared to the traditional AC14 + 2%OPC mixture. The study concludes that LKD is not only an eco-friendly filler aligning with circular economy principles but similarly a technically superior one that significantly improves rutting resistance and durability of asphalt pavements.

The durability of building composites with polymer matrix, such as polymer concretes, is considered high or excellent. However, very few studies are available that show the properties of such composites tested long after the specimens’ preparation, especially composites with fillers other than traditional rock aggregates. The paper presents the long-term compressive strength of polymer concrete containing common and alternative fine fillers, including quartz powder (ground sand) and by-products of the combustion of Polish fossil fuels (coal and lignite), tested nine or 9.5 years after preparation. The results were compiled with the data for respective specimens tested after 14 days, as well as 1.5 and 7 years. Data analysis confirmed the excellent durability of concrete-like composites with various fillers in terms of compressive strength. Density measurements of selected composites showed that the increase in strength was accompanied by an increase in volumetric density. This showed that the opinion that the development of the strength of composites with polymer matrices taking place within a few to several days was not always justified. In the case of a group of tested concrete-like composites with vinyl-ester matrices saturated with fly ashes of various origins, there was a further significant increase in strength over time.

This research activity aims to evaluate electrical insulation system (EIS) intended for electrical machine winding wires. The evaluation is based on mechanical, thermal, and electrical properties tests following international standards for enameled wires. Dielectric parameters such as dissipation factor, partial discharge inception voltage (PDIV), parallel capacitance, and parallel resistance behavior of different insulator configurations on twisted-pair samples are observed during thermal aging tests. Those configurations are formed of different combinations of dielectric layers based on conventional polymers (polyester-imide (PEI), polyamide-imide (PAI), polyimide (PI)) used as coating wires. A study using two mineral varnishes (silica-based) obtained by the sol-gel process integrated on these classical enamels an outer layer of extrusion of thermoplastic polymer with and without mineral fillers. Given the high consummation of energy and the use of unsustainable materials involving the production of wires, the principal interest of this work is to exploit new configurations of coating wire produced, with less environmental impact than conventional ones. This work investigates the impact of filled resins on the performance of insulating samples and the influence of the use of sol-gel solutions (mineral varnishes) on the insulated wire to increase the thermal class.