Search Results (234)

Recently, 3D-printed resins have been introduced as materials for definitive indirect restorations. Herein, a comparative assessment of the bond strengths of 3D-printed resins to a resin cement was performed. Methods: four definitive restorative materials were selected, i.e., a Feldspar ceramic (VITA Mark II, VM), a polymer-infiltrated ceramic network (VITA Enamic, VE), a nanohybrid resin composite (Grandio Bloc, GB), and one 3D-printed resin (Crown Permanent, CP). VM and VE were etched and silanized, GB was sandblasted, and CP was glass bead blasted; for one further experimental group, this was followed by sandblasting (CPs). A resin cement (RelyX Unicem) was then used for bonding, and then a notched shear bond strength test (nSBS) was performed. Failure modes were observed and classified as adhesive, cohesive, or mixed, and SEM representative images were taken. Data were statistically analyzed with one-way ANOVA, Tukey, and Chi-square tests. Significant differences were detected in nSBS among materials (p < 0.001). The highest nSBS was found in VM (30.3 ± 1.8 MPa) a, followed by CP^b, GB^bc, CP^bc, and VE^c. Failure modes were significantly different (p < 0.001), and with different prevalent failure modes. The bond strength for 3D-printed permanent resin materials was shown to be lower than that of the felspathic ceramic but comparable to that of the resin block and PICN substrates. Full article

Prefabricated unidirectional carbon fiber reinforced polymer (CFRP) composite strips are extensively used as a means of infrastructure rehabilitation through adhesive bonding to the external surface of structural concrete elements. Most data to date are from laboratory tests ranging from a few months to 1–2 years providing an insufficient dataset for prediction of long-term durability. This investigation focuses on the assessment of the response of three different prefabricated CFRP systems exposed to water, seawater, and alkaline solutions for 5 years of immersion in deionized water conducted at three temperatures of 23, 37.8 and 60 °C, all well below the glass transition temperature levels. Overall response is characterized through tensile and short beam shear (SBS) testing at periodic intervals. It is noted that while the three systems are similar, with the dominant mechanisms of deterioration being related to matrix plasticization followed by fiber–matrix debonding with levels of matrix and interface deterioration being accelerated at elevated temperatures, their baseline characteristics and distributions are different emphasizing the need for greater standardization. While tensile modulus does not degrade appreciably over the 5-year period of exposure with final levels of deterioration being between 7.3 and 11.9%, both tensile strength and SBS strength degrade substantially with increasing levels based on temperature and time of immersion. Levels of tensile strength retention can be as low as 61.8–66.6% when immersed in deionized water at 60 °C, those for SBS strength can be 38.4–48.7% at the same immersion condition for the three FRP systems. Differences due to solution type are wider in the short-term and start approaching asymptotic levels within FRP systems at longer periods of exposure. The very high levels of deterioration in SBS strength indicate the breakdown of the materials at the fiber–matrix bond and interfacial levels. It is shown that the level of deterioration exceeds that presumed through design thresholds set by specific codes/standards and that new safety factors are warranted in addition to expanding the set of characteristics studied to include SBS or similar interface-level tests. Alkali solutions are also shown to have the highest deteriorative effects with deionized water having the least. Simple equations are developed to enable extrapolation of test data to predict long term durability and to develop design thresholds based on expectations of service life with an environmental factor of between 0.56 and 0.69 for a 50-year expected service life. Full article

To broaden clean asphalt modification methods, this study employs a composite polymer of maleic anhydride-grafted styrene-butadiene-styrene (MA-g-SBS) and styrene-butadiene-styrene (SBS) as a modifier. The composite is formulated into polymer latex and used to modify emulsified asphalt. Routine performance tests were conducted on MA-g-SBS/SBS composite latex-modified emulsified asphalt (MSMEA) with varying ratios to determine the optimal composition. The ideal ratio was found to be MA-g-SBS:SBS = 1:4. Subsequently, conventional property tests, rheological analyses, microphase structure observations, and bending beam creep tests were conducted on MSMEA with the optimal ratio to assess the impact of the composite latex on asphalt performance. Findings indicated that increasing the latex content significantly enhanced the softening point and ductility while reducing penetration. These macroscopic improvements were notably superior to those achieved with single SBS latex modification. Fluorescence microscopy revealed that at low dosages, the MA-g-SBS/SBS composite dispersed uniformly as point-like structures within the asphalt. At higher dosages (above 5%), a distinct network structure emerged. The addition of the composite latex raised the complex shear modulus and rutting factor while reducing the phase angle, with pronounced fluctuations observed between 4% and 5% dosages. This suggests a substantial enhancement in the high-temperature performance of the emulsified asphalt, attributed to the formation of the network structure. FT-IR results confirmed that a chemical reaction occurred during the modification process. Additionally, the bending beam creep test demonstrated that the composite latex reduced asphalt brittleness and improved its low-temperature performance. Full article

To obtain waterborne polymer-modified emulsified asphalt materials with better comprehensive performance, waterborne polymer modifiers including waterborne epoxy resin (WER)-reinforced styrene–butadiene–styrene block copolymer (SBS), waterborne acrylate (WA) or styrene butadiene rubber (SBR) emulsion were prepared. The mechanical strength, toughness, adhesion and impact resistance of these waterborne polymers were evaluated. Furthermore, the correlation between the performance indicators of the waterborne polymers was analyzed. Based on Fourier transform infrared (FTIR) spectroscopy and thermogravimetric (TG) analysis, the mechanism of WER-modified SBS and WA was characterized. The results show that adding 10%–15% WER can significantly improve the mechanical properties of the waterborne polymer. The performances of modified SBS and WA are better than that of modified SBR. When the content of WER is 10%, the tensile strength, elongation at break and pull-off strength of WER-modified SBS and WA are 4.80–6.38 MPa, 476.3%–579.6% and 1.62–1.70 MPa, respectively. The mechanical strength and breaking energy of the waterborne polymers show a significant linear correlation with their application properties such as adhesion, bonding and impact resistance. FTIR and TG analyses indicate that WER-modified SBS or WA prepared via emulsion blending undergo primarily physical modifications, enhancing thermal stability while promoting crosslinking and curing. Full article

This study investigates the performance improvement of asphalt binders through the incorporation of two polymers, polyvinyl chloride (PVC) and styrene–butadiene–styrene (SBS), with asphalt grade (60–70), to address the growing demand for durable and climate-resilient pavement materials, particularly in areas exposed to high temperatures like Iraq. The main objective is to improve the mechanical characteristics, thermal stability, and workability of typical asphalt mixtures to extend pavement lifespan and lessen maintenance costs. A thorough set of rheological, physical, morphological, and workability tests was performed on asphalt binders modified with varying content of PVC (3%, 5%, 7%, and 9%) and SBS (3%, 4%, and 5%). The significance of this research lies in optimizing binder formulations to enhance resistance to deformation and failure modes such as rutting and thermal cracking, which are common in extreme climates. The results indicate that PVC enhances performance grade (PG), softening point, and viscosity, although higher contents (7% and 9%) exceeded penetration grade specifications. SBS-modified binders demonstrated marked improvements in softening point, viscosity, and rutting resistance, with PG values increasing from PG64-x (unmodified) to PG82-x at 5% SBS. Fluorescence microscopy confirmed optimal polymer dispersion at 5% concentration for both SBS and PVC, ensuring compatibility with the base asphalt. Workability testing revealed that SBS-modified mixtures exhibited higher torque requirements, indicating reduced workability compared to both PVC-modified and unmodified binders. These findings offer valuable insights for the design of high-performance asphalt mixtures suitable for hot-climate applications and contribute to the development of more durable and cost-effective road infrastructure. Full article

Antimicrobial resistance arises from treatment non-adherence and ineffective delivery systems. Optimal wound dressings combine localized drug release, exudate management, and bacterial encapsulation through hydrogel-forming nanofibers for enhanced therapy. In this work, polylactic acid (PLA) and polyvinylpyrrolidone (PVP) fibers loaded with chlorhexidine (CHX) were developed using Solution Blow Spinning (SBS), a scalable electrospinning alternative that enables in situ deposition. Molecular interactions between CHX and polymers in solution (by UV-Vis and fluorescence spectroscopy) and in solid state (by FTIR, XRD and thermal analysis) were studied. The morphology of the polymeric fibers was determined by optical microscopy, showing that PVP fibers are thinner (1625 nm) and more uniform than those of PLA (2237 nm). Finally, drug release from single-polymer fibers discs, overlapping fibers discs (PLA/PVP/PLA and PVP/PLA/PVP), and solid dispersions was determined by UV-Vis spectrometry. PVP-based fibers exhibited faster CHX release due to their hydrophilic nature, while PLA fibers proved sustained release, attributed to their hydrophobic matrix. This study highlights the potential of PLA/PVP-CHX fibers made from SBS as advanced wound dressings, combining biocompatibility and personalized drug delivery, offering a promising platform for localized and controlled antibiotic delivery. Full article

It is challenging for mortar to simultaneously enhance the transmission property of water vapor while maintaining excellent waterproofness and impermeability. However, in some applications, both are necessary. Therefore, three different kinds of modifiers, i.e., cementitious capillary crystalline waterproof materials (XYPEX), γ-methacryloxy-propyl-trimethoxy-silane (KH570), and styrene-butadiene rubber latex (SB), are employed to explore how modified mortar can possess excellent waterproofness, impermeability, and the water vapor transmission property simultaneously. Combining characterization techniques, the influencing factors of these three properties are studied. The results indicate that XYPEX promotes the formation of hydration products within pores, improves waterproofness and impermeability, but decreases the water vapor transmission property. KH570 introduces numerous pores ranging from 0.1 to 5 micrometers and enhances the hydrophobicity of mortar; at 1.25% and 2.5% contents, the modified mortar exhibits excellent waterproofness and water vapor transmission property but poor impermeability. SB introduces numerous air pores and forms polymer films; at 20% content, the modified mortar exhibits excellent waterproofness and water vapor transmission property, with impermeability remaining unchanged, making SB a favorable modifier that combines these three properties. Finally, the mechanisms of these three properties are discussed, which provides a theoretical reference for the control of mortar’s waterproofing, impermeability, and water vapor transmission. The selection of modifiers is based on the actual performance requirements. Full article

This study explores the rheological performance of bitumen modified with a synthetic polymer (styrene–butadiene–styrene, SBS) and two environmentally sustainable additives—animal bone ash (AB) and waste cooking oil (WCO)—to enhance durability and deformation resistance under dynamic loading. Frequency sweep and linear amplitude sweep (LAS) tests were conducted to evaluate viscoelastic and fatigue behavior. SBS at 5% showed the highest elasticity and fatigue life, making it optimal for heavily trafficked pavements. Among bio-waste additives, 6% AB provided the highest stiffness and rutting resistance in laboratory tests; however, 5% AB offered a better balance between structural integrity and cracking resistance, making it more suitable for general pavement applications. WCO-modified binders demonstrated improved flexibility, with 4% WCO achieving the best balance between elasticity and softening, ideal for low-load or temperate environments. These results highlight the potential of combining synthetic and bio-based waste materials to tailor bitumen properties for sustainable and climate-responsive pavement design. Full article

Gap-graded asphalt mixtures like stone mastic asphalt (SMA), porous asphalt (PA), and asphalt mixtures for very thin layers (fr. Béton Bitumineuse Très Mince—BBTM) are usually made with the use of SBS (styrene-butadiene-styrene) polymer-modified bitumen. This is a binder that allows one to achieve the required parameters, but at the same time, its use increases the costs of making pavement layers. An alternative to polymer-modified bitumen (SBS) is rubber-modified bitumen. The research presented in this publication includes an assessment of the resistance to permanent deformation and susceptibility to aging of SMA and porous asphalt (PA) mixtures containing both SBS polymer-modified bitumen and rubber-modified bitumen, where the modification process was carried out directly in the refinery. The laboratory tests of resistance to deformation were assessed based on the rutting test and on the assessment of the dynamic modulus (SPT). The changes in the tested asphalt mixtures after aging in laboratory conditions were assessed based on the changes in the stiffness modulus (IT-CY) and the changes in the indirect tensile strength (ITS) after the short-term and long-term aging processes. The presented research results clearly show that the use of rubber-modified bitumen produced in industrial conditions (i.e., in a refinery) allows one to obtain gap-graded mixtures that are as resistant to permanent deformation as mixtures containing SBS polymer-modified bitumen. Similar conclusions resulted from the study of susceptibility to aging. Changes after aging for both types of asphalt mixtures were at a similar level. The presented results clearly indicate that, in the case of gap-graded mixtures such as SMA- and PA-type mixtures, they meet the rutting and aging expectations when either expensive modified bitumen or a cheaper, more environmentally friendly alternative (rubber-modified bitumen) is used. Full article

Compatibilizers play a critical role in resolving compatibility issues between styrene–butadiene–styrene (SBS) modifiers and asphalt systems. These additives enhance the uniform dispersion of SBS modifiers and stabilize their cross-linked network structure within the asphalt matrix. This study employed molecular dynamics (MD) simulations via Materials Studio (MS) to investigate the effects of a compatibilizer on compatibility mechanisms and diffusion behavior in SBS-modified asphalt (SBSMA). Model validation was conducted through density and glass transition temperature (Tg) analyses. The cohesive energy density (CED) and solubility parameters were quantified to assess the impact of compatibilizer dosage on system compatibility. Radial distribution function (RDF) and mean square displacement (MSD) analyses elucidated molecular diffusion dynamics. The results indicate that compatibilizers enhance cohesive energy density by 12.5%, suppress irregular intermolecular motion, and reduce system instability. The synergistic interaction between aromatic and saturated components in compatibilizers effectively disperses asphaltene aggregates and inhibits π–π stacking. Additionally, strong solubility interactions with hydrocarbon mixtures facilitate the diffusion of asphaltene gum molecules. These findings provide molecular-level insights for optimizing compatibilizer design in SBSMA applications. Full article

Water is the most environmentally friendly solvent; however, conventional solution spinning using water as a solvent is challenging due to its low evaporation rate. We developed a double-pronged solution blow spinning (DP-SBS) system. This spinning technique significantly enhances solvent evaporation, and the designed structure (double-pronged) avoids the common problem of needle clogging caused by heating. DP-SBS enables high-yield production of water-soluble polymer nanofibers, with a production rate of up to 5.94 g/h, which far exceeds what can be achieved with traditional electrospinning or solution blow spinning. This method is also highly efficient for producing non-water-soluble polymer nanofibers, achieving a production rate of up to 7.91 g/h, the highest reported value to date. Additionally, this approach can be used to produce not only common two-dimensional fiber membranes but also fiber sponges in a single step using the double-pronged airflow system. For the first time, chitosan nanofiber sponges were successfully produced and demonstrated to have excellent hemostatic properties in medical hemostasis. This method can also be extended to the production of other 3D nanomaterials, such as mullite nanofiber sponges, which exhibit outstanding thermal insulation performance at high temperatures. Full article

It is uncertain whether the interchangeable use of two adhesive systems would yield comparable shear bond strength (SBS) for both Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK); investigating this was the main objective of this study. Milled PEEK (Bredent, Senden, Germany) and PEKK (Pekkton Ivory, AnaxDent, Stuttgart, Germany) blocks were prepared with standardized roughness (0.20 μm) and randomly assigned into two groups (n = 72): with and without aluminum oxide air abrasion (AquaCare Twin, Medivance Instruments, London, UK). Two adhesive systems (Visio.link, Bredent, Senden, Germany, or PEKKBond, AnaxDent, Stuttgart, Germany) were randomly applied (n = 36). Flowable gingival composite (AnaxGum Gingiva, AnaxDent, Stuttgart, Germany) was bonded, and the samples were stored in water (37 °C, 24 h). SBS was measured (MPa) and data were analyzed using three-way ANOVA, followed by Tukey’s test (α = 0.05). All main effects and interactions were significant (p < 0.05), except for polymer (p = 0.163) and the triple interaction (p = 0.601). In the PEEK group, Visiolink showed higher SBS (p < 0.001), regardless of prior air abrasion. For the PEKK group, PEKKBond significantly increased SBS values (p < 0.001) for both pre-treatment groups. Previous air abrasion only significantly increased the SBS of controls without adhesive. This study highlights the importance of material-specific adhesive selection, rather than interchangeable use, for optimal results. The bond strength of PEEK and PEKK is influenced by the adhesive system applied. Moreover, PEKK consistently demonstrated higher SBS values in comparison to PEEK, even without the need for pre-treatment or adhesive conditioning. This characteristic renders PEKK a preferred choice for the fabrication of adhesive restorations. Full article

This study investigates the development of high-performance asphalt binders modified with Trinidad Lake Asphalt (TLA) and styrene–butadiene–styrene (SBS) polymers to enhance pavement durability under extreme climate conditions. A comprehensive evaluation of physical, rheological, and mechanical properties was conducted using Superpave performance tests, Multiple Stress Creep Recovery (MSCR), and a Dynamic Shear Rheometer (DSR). The results indicate that integrating 20% TLA significantly increases stiffness and rutting resistance by 51.7% compared to unmodified PG 64-22 asphalt, while 10% SBS improves elasticity and enhances elastic recovery by 85.3%. However, at 15% SBS, excessive viscosity was observed, reaching 13,000 cP at 135 °C, posing workability challenges and sampling challenges in the lab environment. The MSCR test confirmed that binders modified with 20% TLA and 15% SBS exhibited over 88% recovery and reduced non-recoverable creep compliance (J_nr < 0.01 kPa⁻¹), demonstrating superior resistance to permanent deformation. Additionally, low-temperature rheological testing (BBR at −12 °C) revealed that SBS incorporation mitigates excessive stiffness caused by TLA, improving the binder’s flexibility. These findings underscore the potential of TLA-SBS modified binders in achieving long-lasting, traffic-resilient pavements for extreme climatic conditions. Field validation is recommended to assess long-term feasibility in real-world applications. Full article

The growing demand for electricity in developing countries has called attention and interest to renewable energy sources to mitigate the adverse environmental effects caused by energy generation through fossil fuels. Among different renewable energy sources, such as photovoltaic, wind, and biomass, hydraulic energy represents an attractive solution to address the demand for electricity in rural areas of Colombia that are not connected to the electrical grid. In the current paper, the fluid–structure interaction (FSI) of a recently designed Vertical-Axis Hydrokinetic Turbine (VAHT) Straight-Bladed (SB) Darrieus-type, modified with symmetric winglets, was studied by implementing the sliding mesh method (SMM). By coupling with Computational Fluid Dynamics (CFD) numerical simulations, the FSI study demonstrated that the hydrodynamic loads obtained can cause potential fatigue damage in the blades of the Straight-Bladed (SB) Darrieus VAHT. Fatigue life was assessed using the stress–life (S-N) approach, and materials such as structural steel, short glass fiber reinforced composites (SGFRC), and high-performance polymers (HPP), such as PEEK, were studied as potential materials for the construction of the blades. FSI results showed that the biaxiality index (BI) provides a good understanding of the dominant stresses in the blades as the azimuth angle changes. It was also shown that structural steel and PEEK are good materials for the manufacturing of the blades, both from a fatigue resistance and modal perspective. Full article

The increasing demand for sustainable road construction materials necessitates innovative solutions to overcome the challenges of Recycled Asphalt Pavement (RAP), including aged binder brittleness, reduced flexibility, and durability concerns. Waste Plastic Aggregates (WPA) offer a promising alternative; however, their thermal aging behavior and interactions with RAP remain insufficiently understood. This study evaluates the performance of RAP-based asphalt mixtures, incorporating three types of WPA—Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), and Polypropylene (PP)—under three thermal aging conditions: mild (60 °C for 7 days), moderate (80 °C for 14 days), and severe (100 °C for 30 days). The mixtures were designed with 30% RAP content, 10% and 20% WPA by aggregate weight, and SBS-modified binder rejuvenated with 2% and 4% sewage sludge bio-oil by binder weight. It is considered that thermal aging may impact the performance of WPA in RAP mixtures; therefore, this study evaluates the durability and mechanical properties of RAP mixtures incorporating LDPE, HDPE, and PP under varying thermal aging conditions to address these challenges. The results showed that incorporating WPA and bio-oil significantly enhanced the mechanical performance, durability, and sustainability of asphalt mixtures. Marshall Stability increased by 12–23%, with values ranging from 12.6 to 13.2 kN for WPA-enhanced mixtures compared to 12.7 kN for the control. ITS improved by 15–20% in dry conditions (1.34–1.44 MPa) and 12–18% in wet conditions (1.15–1.19 MPa), with TSR values reaching up to 82.64%. Fatigue life was extended by 28–43%, with load cycles increasing from 295,600 for the control to 352,310 for PP mixtures. High-temperature performance showed a 12–18% improvement in softening point (57.3 °C to 61.2 °C) and a 23% increase in rutting resistance, with rut depths decreasing from 7.1 mm for the control to 5.45 mm for PP mixtures after 20,000 passes. These results demonstrate that combining RAP, WPA, and bio-oil produces sustainable asphalt mixtures with superior performance under aging and environmental stressors, offering robust solutions for high-demand applications in modern infrastructure. Full article