Search Results (305)

This study aimed to evaluate the impact of different adhesive solutions on the surface roughness and hardness of denture base materials. Twenty specimens (20 × 20 × 5 mm) were produced for each material group: heat-cured ProBase Hot^®, 3D-printed NextDent Denture 3D+^®, and PMMA-milled Exaktus^®. They were then divided into five solution subgroups (n = 4): control (T0), distilled water, Corega PowerMax^®, Elgydium Fix^®, and Kukident Pro Ultimate^®. Specimens were immersed in the solution at 37 °C daily for 28 days, simulating continuous use. Profilometry and Shore D hardness tests were performed at baseline and after 28 days of the immersion protocol. Data analysis was done using IBM SPSS Statistics 30.0, considering a confidence level of 0.05. At baseline, the materials differed in surface roughness and Shore D hardness, with the 3D-printed group showing the highest median values for the Rz parameter (p = 0.023) and the lowest for hardness (p = 0.023). Elgydium Fix had a significant effect on the heat-cured resin, with increased Rz and decreased hardness. Kukident caused higher roughness and lower hardness in the 3D-printed and milled resins (not significant). Corega showed minor effects in all tested materials. In conclusion, the denture base material and the adhesive formulation influence the physical and mechanical properties of denture base resins. Full article

The reintegration of waste into the production chain represents a sustainable method of reducing environmental impact while promoting economic growth. This also aligns with social and environmental demands. In this study, composites were produced from commercial and recycled gypsum, polyvinyl acetate (PVA) emulsions, and chemically treated short green coconut fibers, and characterized by physical and mechanical analyses. The addition of PVA improved paste workability, extended setting time, and reduced porosity, while fiber pretreatment enhanced adhesion and tensile performance. XRD, FTIR, and TGA-DTA confirmed modifications in crystallinity, bonding, and thermal stability due to the combined action of PVA and fibers. Compared with the recycled gypsum reference (RG), the optimized composite (R50C50P5F10) exhibited a 69.1% reduction in sorptivity (from 5440 × 10⁻⁴ to 1680 × 10⁻⁴ kg/m²·s^0.5), a 27.9% increase in flexural tensile strength (from 2.65 to 3.39 MPa), and a 15.1% increase in compressive strength (from 6.18 to 7.12 MPa). Surface hardness values remained statistically equivalent to RG but complied with normative requirements, maintaining all formulations within the moderate hardness category (55–80 Shore C). The results demonstrate the technical feasibility of incorporating recycled gypsum and agro-industrial fibers into gypsum composites, providing a sustainable route for developing more durable construction materials. Full article

Polymeric nanocomposites have been extensively investigated due to their potential for enhancing the mechanical and tribological properties of polymer composites. In this study, the mechanical performance of carbon fiber-reinforced epoxy composites modified with nano-sized ferrochrome slag particles, an industrial by-product from stainless steel manufacturing, was evaluated. Composite laminates were fabricated using a vacuum-assisted hand lay-up process, with consistent carbon fiber reinforcement and uniformly dispersed nanofillers in the epoxy matrix. Mechanical properties such as tensile, flexural, impact, and Shore D hardness were evaluated as per ASTM and ISO standards. At 2 wt.% nanofiller loading, enhanced tensile strength and hardness by 33.02% and 8.92%, respectively, were achieved, while flexural strength and impact strength increased by 3.70% and 3.62% at 1 wt.% compared to the neat composite. Higher filler contents (>3 wt.%) resulted in reduced performance due to particle agglomeration and microstructural inhomogeneity. A scanning electron microscope was used to determine the uniform dispersion and agglomeration of nanofillers. The results demonstrated the potential of ferrochrome slag as a sustainable and cost-effective nanofiller for advanced composite applications. Full article

This study describes the design and validation of an experimental setup for testing photoplethysmographic (PPG) devices intended for the non-invasive monitoring of vascular accesses in hemodialysis patients. Continuous assessment of arteriovenous fistulas is essential to detect pathological conditions such as stenosis, which can compromise patient safety and dialysis efficacy. While PPG-based sensors are capable of detecting such anomalies, their clinical applicability must be supported by controlled in vitro validation. The developed system replicates the anatomical, mechanical, optical, and hemodynamic features of vascular accesses. A 3D fistula model was designed and fabricated via 3D printing and silicone casting. The hydraulic circuit used red India ink and a PWM-controlled pump to simulate physiological blood flow, including stenotic conditions. Quantitative validation confirmed anatomical accuracy within 0.1 mm tolerance. The phantom exhibited an average Shore A hardness of 20.3 ± 1.1, a Young’s modulus of 10.4 ± 0.9 MPa, and a compression modulus of 105 MPa—values consistent with soft tissue behavior. Burst pressure exceeded 2000 mmHg, meeting ISO 7198:2016 standards. Flow rates (400–700 mL/min) showed <1% error. Compliance was 2.4 ± 0.2, and simulated blood viscosity was 3.9 ± 0.3 mPa·s. Systolic and diastolic pressures fell within physiological ranges. Photoplethysmographic signals acquired using a MAX30102 sensor (Analog devices Inc., Wilmington, MA, USA) reproduced key components of in vivo waveforms, confirming the system’s suitability for device testing. Full article

The main goal of a garlic planter is to plant garlic cloves individually with even spacing, requiring minimization of missed or multiple plantings. This study adopted an air-suction metering device to increase planting speed. To handle irregularly shaped garlic cloves effectively, soft silicone suction holes were fabricated and attached to the metering device. Performance was assessed by varying suction hole diameters (8, 11, 14, and 17 mm) and material hardness levels (1.4, 16.7, and 27.2 HA Shore A) at multiple-metering rates. The optimal metering rate of 98.2% was achieved with a 14 mm suction hole diameter and 16.7 HA hardness. This success was attributed to the soft suction hole effectively conforming to the garlic clove surface. The findings revealed a critical limitation: when metering rates exceeded 90%, multiple-metering rates increased linearly, indicating inherent constraints of air-suction techniques for single-seed metering. These results provide valuable insights into design parameters needed to improve reliability, operational efficiency, and mechanization performance of garlic planters. The metering device type is expected to be applicable to autonomous or unmanned agricultural machines, advancing agricultural mechanization capabilities. Full article

This study explores the mechanical characteristics of 3D-printed specimens fabricated using TPU-95A filament, with a focus on the influence of key printing variables—temperature, speed, and layer height—on tensile strength, toughness, and surface hardness. Through systematic testing, the tensile evaluation revealed a peak tensile strength of 329.02 kgf/cm² and toughness of 1.56 under conditions of elevated temperatures and optimized layer configurations. Similarly, the hardness assessment indicated a maximum average value of 74.9 Shore A, emphasizing the substantial effect of process parameters on material integrity and resilience. A detailed variance analysis confirmed the pivotal roles of temperature and layer height in enhancing mechanical properties. Using a statistical optimization approach, optimal printing conditions were identified, demonstrating that higher temperatures, moderate speeds, and reduced layer heights significantly improve the balance between strength, flexibility, and durability. These findings contribute to the development of tailored fabrication strategies, offering practical insights for applications where precision and mechanical reliability are critical. Full article

Auxetic structures, also known as metamaterials, exhibit a negative Poisson’s ratio under applied load and have found use across a variety of applications. This behavior may arise from material properties or from the structural design itself. Depending on the intended application, such structures can be subjected to either static or dynamic loading conditions. New geometries that potentially enhance energy absorption or damping in both static and dynamic conditions were investigated in this work, using the well-known Reentrant design reported in earlier research articles as a benchmark. As an alternative to the cellular limb angles employed in the well-known Reentrant model, the effect of radial limb radius was analyzed in the novel cell designs called Arched-Reentrant. Four alternative designs have been proposed, and all analyses were conducted in ANSYS-2025-R1. The specimens were manufactured by using the 3D printing method with thermoplastic polyurethane (TPU) material having a shore hardness of 95A. In the evaluation of the outcomes resulting from different designs, the specimens were analyzed under static, impulsive, and harmonic loading conditions. The energy absorption capacities of the samples were examined in relation to their design modifications. Within the scope of the study, it was observed that Arched-Reentrant structures are capable of absorbing higher amounts of energy under static loading and exhibit greater stiffness under dynamic loads compared to conventional Reentrant structures. The impulse analysis’s findings demonstrate that the suggested Arched-Reentrant-V3 model performs better, with over 50% less displacement and comparable reaction forces. In addition, the harmonic analysis findings show that the Arched-Reentrant-V3 model has lower ground reaction forces and displacement values. As a result, the suggested model can be regarded as an efficient damping component when dynamic loading occurs. Full article

Polytetrafluoroethylene (PTFE) is one of the alternative materials suitable for seawater-lubricated bearings, favored for its excellent corrosion resistance and good self-lubricating properties. As marine equipment develops towards higher load, higher reliability, and longer service life, more stringent requirements are imposed on the wear resistance of bearing materials. However, traditional PTFE materials struggle to meet the performance requirements for long-term stable operation in modern marine environments. To improve the wear resistance of PTFE, this study used alumina (Al₂O₃) particles with three different particle sizes (50 nm, 3 μm, and 80 μm) as fillers and prepared Al₂O₃/PTFE composites via the cold pressing and sintering process. Tribological performance tests were conducted using a ball-on-disk reciprocating friction and wear tester, with Cr12 steel balls as counterparts, under an artificial seawater lubrication environment, applying a normal load of 10 N for 40 min. The microstructure and wear scar morphology were characterized by scanning electron microscopy (SEM), and mechanical properties were measured using a Shore hardness tester. A systematic study was carried out on the microstructure, mechanical properties, friction coefficient, wear rate, and limiting PV value of the composites. The results show that the particle size of Al₂O₃ particles significantly affects the mechanical properties, friction coefficient, wear rate, and limiting PV value of the composites. The 50 nm Al₂O₃/PTFE formed a uniformly spread friction film and transfer film during the friction process, which has better friction and wear reduction performance and load bearing capacity. The 80 μm Al₂O₃ group exhibited poor friction properties despite higher hardness. The nanoscale Al₂O₃ filler was superior in improving the wear resistance, stabilizing the coefficient of friction, and prolonging the service life of the material, and demonstrated good seawater lubrication bearing suitability. This study provides theoretical support and an experimental basis for the design optimization and engineering application of PTFE-based composites in harsh marine environments. Full article

Polymer viscoelasticity is crucial for mechanical performance, but conventional low-frequency methods struggle to isolate viscous loss—a key viscosity indicator. This study introduces a high-frequency ultrasonic method to differentiate the polymer viscous dissipation index by analyzing acoustic phase shifts. We employ ultrasonic phase-shift thermometry to measure localized temperature increases resulting from minute variations in sound velocity during controlled heating. This allows for the quantification of viscous loss, which is then used to distinguish between different polymer formulations. Experimental and simulation results on a series of polyurethane specimens with varying Shore hardness levels demonstrate that decawatt-range (10–20 W) ultrasonic irradiation enables sensitive and precise differentiation. Notably, the Shore A70 polyurethane sample exhibited a significantly higher viscous dissipation index, evidenced by the largest temperature rise (27.5 °C) and the highest proportion of viscous heating to total power dissipation (93.1%) under 17 W acoustic irradiation. While this study focuses on commercially available polymers, the method can be extended to evaluate key performance parameters, such as tensile modulus and glass transition temperature, in polymers fabricated under various processing conditions, thereby offering a powerful tool for material quality assessment. Full article

Different polyurethanes (PURs) and silicone for potential use in particle accelerators and detectors have been characterized in the uncured state, after curing, and after exposure to ionizing irradiation in ambient air and in liquid helium. The viscosity evolution during processing was measured with a rheometer. Dynamic mechanical analysis (DMA) and Shore A hardness measurements were applied to detect irradiation-induced crosslinking and chain scission effects. Uniaxial tensile and flexural tests under ambient and cryogenic conditions have been performed to assess changes in mechanical strength, elongation at break, and elastic properties. The initial viscosity of 550 cP at 25 °C of the uncured PUR RE700-4 polyol and RE106 isocyanate system for protective encapsulation is sufficiently low for impregnation of small magnet coils, but the pot life of about 30 min is too short for impregnation of large magnet coils. The cured RE700-4 system has outstanding mechanical properties at 77 K (flexural strength, impact strength, and fracture toughness). When RE700-4 is exposed to ionizing radiation, chain scission and cross-linking occur at a similar rate. In the other casting systems, irradiation-induced changes are cross-linking dominated, as manifested by an increase of the rubbery shear modulus (G’_rubbery), the ambient temperature Young’s modulus (E_RT), and the Shore A hardness. Cross-linking rates are strongly reduced when irradiation occurs in liquid helium. The irradiation effect on mechanical properties can be strongly dependent on the testing temperature. The RT mechanical strength and strain at fracture of the cross-linking silicone is drastically decreased after 1.6 MGy, whereas its 77 K strain at fracture has almost doubled. In addition, 77 K elastic moduli are similar for all pure resins and only slightly affected by irradiation. Full article

Novel polyester–polyurethane polymeric materials were formulated by combining a natural aliphatic polyester, poly(3-hydroxybutyrate) (P3HB), with a synthetic aliphatic polyurethane via melt blending. The resulting fully biodegradable compositions were functionally modified through the incorporation of urea, with the aim of enabling post-consumer utilization of the material residues as nitrogen-rich fertilizers. The fabrication process was systematically established and optimized, focusing on homogeneous blending and processability. Comprehensive mechanical characterization—including tensile strength, impact resistance, and Shore hardness—was performed. Among the tested formulations, composites containing 1 wt.% urea demonstrated superior mechanical performance and optimal processing behavior. Fourier-transform infrared (FTIR) spectroscopy was employed to investigate molecular-level interactions between polymeric phases and urea, while scanning electron microscopy (SEM) was utilized to assess the morphological characteristics of the resulting biocompositions. Comparative analyses of the physico-mechanical properties and biodegradability were conducted among the urea-modified compositions, binary P3HB–polyurethane blends, and neat P3HB. The observed improvements in mechanical integrity and functional biodegradability suggest that the developed urea-enriched compositions are promising candidates for the fabrication of eco-friendly seedling pots via injection molding technology. Full article

By proportionally blending fresh latex from PR107, Reyan 72059, and Reyan 73397, and employing both acid- and enzyme-assisted microbial coagulation methods, this study analyzed the effects of the specific latex formulation on the following: physicochemical properties, non-rubber components, molecular weight and distribution, vulcanization characteristics of compounded rubber, and physical–mechanical properties of vulcanized natural rubber. The results indicate that, compared to acid-coagulated natural rubber, enzyme-assisted microbial coagulated natural rubber exhibits slightly lower levels of volatile matter, impurities, plasticity retention index (PRI), nitrogen content, calcium ions (Ca²⁺), iron ions (Fe³⁺), and fatty acid content. Conversely, it demonstrates higher values in ash content, initial plasticity (P₀), Mooney viscosity (M_L(1+4)), acetone extract, magnesium ions (Mg²⁺), copper ions (Cu²⁺), manganese ions (Mn²⁺), gel content, molecular weight and distribution, and glass transition temperature (Tg). With the increase in the proportion of PR107 and Reyan 72059 fresh latex, the ash content, volatile matter content, fatty acid content, gel content, and dispersion coefficient (PDI) of natural rubber gradually decrease, while the impurity content, PRI, nitrogen content, weight-average molecular weight (Mw), and number-average molecular weight (Mn) gradually increase. Compared to acid-coagulated natural rubber compounds, enzyme-assisted microbial-coagulated natural rubber compounds exhibit higher minimum torque (M_L) and maximum torque (M_H), but shorter scorch time (t₁₀) and optimum cure time (t₉₀). Furthermore, as the proportion of PR107 and Reyan 72059 fresh latex increases, the ML of the compounds gradually decreases. In pure rubber formulations, enzyme-assisted microbial-coagulated natural rubber vulcanizates demonstrate higher tensile strength, tear strength, modulus at 300%, and Shore A hardness compared to acid-coagulated natural rubber vulcanizates. When the fresh latex ratio of PR107, Reyan 72059, and Reyan 73397 is 1:1:3, the tensile strength and 300% modulus of the natural rubber vulcanizates reach their maximum values. In carbon black formulations, the tensile strength and tear strength of enzyme-assisted microbial-coagulated natural rubber vulcanizates are significantly higher than those of acid-coagulated natural rubber vulcanizates in pure rubber formulations, with the increase exceeding that of other samples. Full article

Alzheimer’s disease is the most widespread neurodegenerative disease in the world. Galantamine hydrobromide (GH) is one of the drugs used to treat mild to moderate dementia of the Alzheimer type. Due to the fact that the specificity of the disease requires maximally facilitated intake, orodispersible films present such an opportunity. In the present study orodispersible films based on poly(2-ethyl-2-oxazoline) as well as partially hydrolyzed poly(2-ethyl-2-oxazoline) were prepared and studied as delivery systems for GH. Two samples of partially hydrolyzed PEtOx were synthesized—one of relatively low degree of hydrolysis and another one of relatively high degree of hydrolysis, and studied by Nuclear Magnetic Resonance (NMR). Cytotoxicity assay was performed that validated the low hydrolyzed derivative as biocompatible polymer that maintained desirable physicochemical characteristics without compromising the safety, thereby it was selected for further research. The films were prepared by the solution casting method and characterized by different methods. FTIR was used to determine the potential interactions between the galantamine molecule and the film components. Based on the Thermogravimetric Analysis (TGA) conducted, it was concluded that all films were sufficiently thermally stable, as the component decomposition stage (after initial solvent removal) began above 180 °C. The polymer films were further characterized with the determination of Shore hardness and the results showed that the films containing glycerol as a plasticizer exhibited higher hardness compared to those with PEG as a plasticizer. The disintegration time of the films was determined visually using Petri dishes and it was found that the films disintegrated within the range of 0.52 to 1.58 min, fully meeting the pharmacopoeial requirements. GH release profiles in PBS at 37 °C were obtained, and it was found that by the second minute, 80–90% of the drug were released from the different films, and the release followed an anomalous diffusion mechanism (Case II). Full article

This study investigates the interplay between infill structure and surface texture in Fused Deposition Modeling (FDM)-printed polymer specimens and their combined influence on tribological and mechanical performance. Unlike previous works that focus on single-variable analysis, this work offers a comparative evaluation of Shore D hardness and coefficient of friction (COF) for PLA and Iglidur materials, incorporating diverse infill patterns. The results reveal that specific combinations (e.g., grid infill with 90% density) optimize hardness and minimize friction, offering practical insights for design optimization in functional parts. Our aim is to provide design insights for enhanced wear resistance and hardness through tailored structural configurations. Carbon Fiber-reinforced PLA (PLA CF), aramid fiber-reinforced Acrylonitrile Styrene Acrylate (Kevlar), and Iglidur I180-BL tribofilament. Disc specimens were fabricated with gyroid infill densities ranging from 10% to 100%. Experimental methodologies included Ball-on-Disc tests conducted under dry sliding conditions (5 N normal load, 150 mm/s sliding speed) to assess friction and wear characteristics. These tribological evaluations were complemented by profilometric and microscopic analyses and Shore D hardness testing. The results show that Iglidur I180-BL achieved the lowest friction coefficients (0.141–0.190) and negligible wear, while PLA specimens with 90% infill demonstrated a polishing-type wear with minimal material loss and a friction coefficient (COF) of ~0.108. In contrast, PLA CF and Kevlar exhibited higher wear depths (up to 154 µm for Kevlar) and abrasive mechanisms due to fiber detachment. Shore hardness values increased with infill density, with PLA reaching a maximum of 82.7 Shore D. These findings highlight the critical interplay between infill architecture and surface patterning and offer actionable guidelines for the functional design of durable FDM components in load-bearing or sliding applications. Full article

This study investigates the mechanical, morphological, and wear properties of SiO₂-filled tri-axial warp-knitted (TWK) glass fiber-reinforced vinyl ester matrix composites, with a focus on void fraction, tensile, flexural, hardness, and wear behavior. Adding SiO₂ fillers reduced void fractions, enhancing composite strength, with values ranging from 1.63% to 5.31%. Tensile tests revealed that composites with 5 wt% SiO₂ (GV1) exhibited superior tensile strength, Young’s modulus, and elongation due to enhanced fiber–matrix interaction. Conversely, composites with 10 wt% SiO₂ (GV2) showed decreased tensile performance, indicating increased brittleness. Flexural tests demonstrated that GV1 outperformed GV2, showcasing higher flexural strength, elastic modulus, and deflection, reflecting improved load-bearing capacity at optimal filler content. Shore D hardness tests confirmed that GV1 had the highest hardness among the specimens. SEM analysis revealed wear behavior under various loads and sliding distances. GV1 exhibited minimal wear loss at lower loads and distances, while higher loads caused significant matrix detachment and fiber damage. These findings highlight the importance of optimizing SiO₂ filler content to enhance epoxy composites’ mechanical and tribological performance. Full article