Search Results (435)

This study evaluated the partial and total replacement of zinc oxide (ZnO) with magnesium oxide (MgO) in styrene–butadiene rubber (SBR) composites, as well as the incorporation of ground tire rubber (GTR), aiming to develop more sustainable elastomer formulations. Ten formulations were prepared with varying ZnO/MgO ratios (100/0 to 0/100), with and without 20 phr of GTR. The composites were characterized by particle size distribution, morphology, rheometric behavior, density, crosslink density, mechanical properties, abrasion resistance, compression behavior, and thermo-oxidative aging. The results showed that hybrid ZnO/MgO activation systems exhibited a synergistic effect, enhancing vulcanization kinetics and mechanical performance compared to single-activator systems. Total replacement of ZnO by MgO was less effective, leading to reduced crosslink density and inferior properties. The addition of GTR increased compound viscosity and altered morphology but improved abrasion and compression resistance without significantly affecting tensile strength. Aging tests indicated good thermal stability, with maintenance or improvement of tensile properties due to post-curing effects. Overall, the combination of reduced ZnO content with MgO and GTR represents a viable approach for producing SBR composites with adequate performance and lower environmental impact. Full article

Conductive core–shell superabsorbent polymers (SAPs) are emerging as multifunctional additives for cementitious materials, combining moisture management with electrical functionality. In cement-based systems, a swellable polymeric core enables internal curing and crack-sealing through controlled water uptake and release, while a conductive shell introduces ionic and/or electronic charge transport, addressing key limitations of conventional non-conductive SAPs. This dual functionality provides a pathway toward smart cementitious composites with enhanced durability, self-sensing capability, and moisture-responsive behavior. This review focuses on the physical chemistry mechanisms governing conductive core–shell SAPs in cementitious environments, with emphasis on swelling thermodynamics, water transport kinetics, interfacial phenomena, and charge transport mechanisms. The roles of osmotic pressure, elastic network constraints, ionic effects, and pore solution chemistry are critically discussed, together with their impact on conductivity, hydration processes, microstructure development, and long-term performance. The relative contributions of ionic and electronic conduction are examined in relation to hydration state, shell morphology, and percolation of conductive networks. In addition, the relevance of core–shell SAP architectures to sustainable packaging is briefly discussed as a secondary application, illustrating how similar physicochemical principles—such as moisture buffering and functional coatings—apply beyond construction materials. Finally, key knowledge gaps are identified, including long-term stability in highly alkaline environments, trade-offs between swelling capacity and conductivity, environmental impacts of conductive phases, and the need for integrated experimental and modeling approaches. Addressing these challenges is essential for the rational design and practical implementation of conductive core–shell SAPs in next-generation cementitious materials. Full article

Aligned CS/Rx aerogels were fabricated by inducing non-directional ice growth (freeze-molding) followed by low-temperature curing, resulting in monoliths with interconnected channels, a high void fraction, and moldability. The swelling index (S%) was calculated to be 1029, the apparent density 0.496 g·cm⁻³, and the estimated porosity 90% based on micrographic analysis. Aerogels have mechanical behavior Shore A hardness greater than 25. Batch metal removal tests were performed (10 mL, 100 mg·L⁻¹ Cr(VI), 0.19 g adsorbent, 24 h, and pH 5–5.5), and the material achieved 95% metal removal. Additional kinetic and isothermal results were obtained using CS85R15 on a packed column (20 to 140 mg·L⁻¹, 1000 mL Cr(VI), 0.80 g adsorbent, 24 h, and pH 5–5.5). Equilibrium data were consistent with a heterogeneous surface hosting a specific site, as reflected in the joint Freundlich/Langmuir fit (q_max 100.8 mg·g⁻¹ for Langmuir). This confirmed the preservation of chitosan functionalities (–OH/–NH) after processing, while XPS detected chromium on the surface with signals consistent with the partial reduction of Cr(VI) to Cr(III) on the aerogel surface. This highlights the relevance of adsorption-based technologies for water remediation, where high-porosity and low-density materials allow for short diffusion pathways and capture electrostatics by protonated amines and redox conversion of hazardous substances. The soft-cure freeze-molding technique is simple, scalable, and compatible with packed-bed/column operation, providing a material platform for tailoring the microstructure (sheets and channels) and surface chemistry to regenerable sorbents for industrial wastewater treatment. Full article

In liquid composite moulding processes, the curing behaviour of thermoset matrices plays a decisive role in determining manufacturing quality and cycle time. Premature demoulding may lead to insufficiently cured components, whereas excessively long curing times reduce production efficiency. Reliable monitoring and modelling of the curing process are therefore essential for process optimisation. In this study, the cure kinetics of a fast-curing epoxy resin system are modelled using the Grindling kinetic model, which accounts for diffusion-controlled reaction behaviour and vitrification effects. Model parameters are identified using both dynamic and isothermal differential scanning calorimetry (DSC) measurements. In addition, the glass transition temperature is described as a function of the degree of cure using the DiBenedetto relationship. To demonstrate the applicability of the model for process monitoring, an experimental mould equipped with temperature sensors was developed to simulate real-time estimation of the degree of cure during isothermal processing. The predicted degree of cure is validated by post-process DSC analysis of the manufactured samples. Initial comparisons reveal systematic deviations caused by temperature measurement uncertainties. After implementing a temperature correction based on experimentally determined sensor deviations, the predicted degree of cure shows significantly improved agreement with DSC measurements. The results demonstrate that combining kinetic modelling with temperature monitoring enables reliable real-time estimation of the curing state for fast-curing epoxy systems. The study also highlights the critical importance of accurate temperature measurement for curing monitoring and provides insights into the practical implementation of sensor-based monitoring strategies in liquid composite moulding processes. Full article

This study investigates the residual stresses developed during the curing process of polymer fiber-reinforced composites and their influence on fracture behavior, particularly the initiation and propagation of interlaminar cracks. The main objective is to quantify how different curing histories, including incomplete cure, alter the spatial distribution of residual stresses and, in turn, affect the mode-I fracture response of carbon-fiber/epoxy laminates. A transient thermal–structural finite element framework incorporating an autocatalytic cure kinetics model was used to simulate the curing process and predict residual stress development in a unidirectional carbon-fiber/epoxy laminate with an edge crack, considering thermal, chemical, and geometric effects. The cure model was calibrated using isothermal differential scanning calorimetry data to determine the degree of cure under different thermal conditions. The key novelty of this work is the integration of a validated cure-kinetics-based curing simulation with fracture analysis, enabling direct correlation of thermal history and degree of cure with spatially varying residual stresses at the crack front and their effect on fracture toughness. Numerical load–displacement predictions were compared with double cantilever beam experimental results and showed good agreement for the curing profiles examined. The results demonstrate that residual stresses generated by different cure cycles, including hold conditions and incomplete curing, significantly influence fracture toughness. In particular, the incomplete-cure profile produced an approximately 40% reduction in toughness compared with profiles that achieved complete cure, highlighting the importance of cure history in determining final structural performance. Full article

Fiber-reinforced cemented tailings backfill (FTB) has been widely adopted in underground mining operations as an effective solution for mitigating the brittleness of cemented tailings backfill (CTB) and ensuring compatibility with deep mining environments. Understanding the coupled effects of temperature and binder composition on the thermal–hydro–mechanical–chemical (THMC) behavior of FTB is essential for low-carbon mix design and practical application. To address this knowledge gap, this work presents a systematic investigation into the influences of curing temperature, binder type, and cement content on the rheological properties, compressive strength, and THMC-related parameters of FTB. The results demonstrate that elevated temperatures accelerate hydration, reducing flowability while significantly enhancing strength and pore structure refinement. Conversely, low temperatures preserve flowability but impede strength development. The incorporation of slag or fly ash as partial cement substitutes reduces rheological parameters; however, fly ash substitution tends to compromise ultimate strength. Multi-field performance monitoring further reveals the underlying coupling mechanisms among temperature evolution, hydration kinetics, matric suction, and mechanical strength development. Based on these insights, a low-carbon design strategy is proposed, emphasizing dynamic optimization of cement content according to ambient temperature. These findings offer a theoretical foundation for the sustainable proportioning and performance control of mine backfill materials. Full article

Growing interest in developing sustainable materials that reduce dependence on fossil resources has led to increased development of bio-based elastomers that can compete with traditional materials in terms of performance when reinforced with additives. This study shows that functionalizing graphene oxide with different alkylamine chains (C8, C12, and C16) enables precise, multidimensional modulation of polymyrcene rubber (PMy) composite behavior. The main finding is that there is a critical concentration of ~1.5–2.0 phr and an optimal chain length of C16 that maximizes mechanical strength, elongation, and toughness simultaneously, thus avoiding the classic trade-off between stiffness and extensibility. Additionally, the study reveals biphasic behavior of graphene oxide modified with dodecylamine (GO_A12) on curing kinetics. At low concentrations, GO_A12 slows vulcanization by competing with accelerators, while at higher concentrations, it accelerates vulcanization via Zn–amine–sulfur complexes. This duality is reflected consistently in the crosslink density, Payne effect, and tensile properties, establishing a coherent structure–property correlation. Identifying an optimal crosslinking regime of ~8.5 × 10⁻⁴ mol/cm³ as the common denominator of the best formulations provides a rational design guide for high-performance elastomers based on renewable matrices and graphene-derived reinforcements. The decrease in tan δ observed through mechanical dynamic analysis suggests potential applications in the tire industry due to increased energy dissipation, which would improve fuel efficiency. Full article

To enhance the early-age properties of steel slag cement mortar and promote the resource utilization of metallurgical solid waste, in this study, nano-SiO₂ (KH-NS) was modified using a KH550 silane coupling agent. The hydration kinetics and microstructure evolution were systematically analyzed by means of a macroscopic performance test (setting time and compressive strength) and multi-scale microscopic characterization (characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, X-ray Diffraction, Thermogravimetry-Differential Thermal Analysis, and isothermal calorimetry). The influence mechanism of its content on the early performance of the steel slag cement system was systematically studied. Research findings indicate that at a given dosage, increasing the proportion of KH-NS results in a shorter setting time for steel slag mortar. When the KH-NS dosage reaches 1.5%, the initial and final setting times of steel slag mortar decrease by 24.21% and 21.20%, respectively. The addition of KH-NS effectively enhances the compressive strength of mortar, with a particularly pronounced effect on early strength prior to 14 h of curing. At a KH-NS dosage of 1.5%, the onset of the accelerated phase of hydration heat release in steel slag cement mortar is advanced by 2.5 h. Mechanistic studies indicate that KH-NS accelerates cement hydration by promoting C₃S dissolution and C-S-H gel nucleation through interactions between surface silanol groups (Si-OH) and amino groups (-NH₂). Furthermore, KH-NS refines the pore structure via a micro-aggregate filling effect, reducing the number of harmful pores and improving the pore size distribution. KH-NS continuously consumes Ca(OH)₂ through pozzolanic reactions to generate C-S-H, with its reactivity increasing with higher dosage. Research confirms that KH-NS significantly enhances the early strength and density of steel slag mortar, providing both theoretical justification and technical support for developing low-carbon building materials based on solid waste with high dosage. Full article

The aim of this study is to evaluate the influence of traditional and industrial smoking technologies on the physicochemical properties, color, texture, and mass loss of selected cured pork products. Four products (dry-cured pork neck, dry-cured pork loin, pancetta, and fermented sausages in natural and collagen casings) were produced using two smoking regimes (traditional and industrial). The samples were analyzed at two processing stages, after smoking and at the end of the production process. Physicochemical composition, pH, water activity (a_w), color parameters (CIE L*a*b*), texture profile parameters, and mass loss were determined using standard analytical methods. Statistical differences between treatments were evaluated using the analysis of variance (ANOVA) followed by Fisher’s least significant difference (LSD) test (p < 0.05). Traditional smoking resulted in greater dehydration, with moisture content reduced by approximately 8–15% and water activity lower by about 0.04–0.09 compared with industrial smoking. Traditionally smoked products also showed higher mass loss (up to 10–12%) and lower L* values, indicating darker color. Texture profile analysis indicated higher hardness values in several traditionally smoked products, particularly in sausages and pancetta. In contrast, industrial smoking resulted in higher moisture retention and more uniform physicochemical characteristics. The differences between smoking regimes were less pronounced in dry-cured pork neck. These results demonstrate that smoking technology significantly influences dehydration dynamics and several technological quality parameters of cured meat products, providing useful information for optimizing smoking regimes in traditional and industrial meat processing. Full article

Unsaturated polyester resin (UPR)–quartz composites have become increasingly important in structural, sanitary, and architectural applications. However, their manufacturing processes still rely heavily on empirical knowledge. This review compiles recent developments in materials science, curing kinetics, and digital manufacturing, outlining a pathway toward data-driven, adaptive production of quartz-filled thermosets. The chemical and physical fundamentals of UPR polymerization are summarized, including the influence of initiator systems, filler characteristics, and thermal management on network formation. Challenges associated with highly filled formulations—such as viscosity control, dispersion, shrinkage, and exothermic peak prediction—are discussed in detail. Recent advances in digital twins (DTs) and artificial intelligence (AI) are reviewed, demonstrating how physics-based simulations, machine learning models, and hybrid mechanistic–data-driven approaches improve the prediction of rheology, curing behavior, and quality outcomes in thermoset polymer processes. A practical application example demonstrates the prediction of peak time in quartz–UPR composites using Random Forest and Gradient Boosting ensemble models. Two prediction scenarios are evaluated: Scenario A with gel time by Leave-One-Out cross-validation, and Scenario B without gel time, representing post-mixing and pre-process prediction contexts, respectively. Stratified bootstrap augmentation improves Gradient Boosting in both scenarios. Principal component analysis confirms that the curing process is governed by three independent physical dimensions: curing reactivity, thermal environment and resin thermal state. Full article

Dynamic mechanical thermal analysis (DMTA) is widely used to assess the effects of process- and environment-induced changes in polymer matrix composites, with the glass transition temperature (T_g) often reported from the tan d peak at a single excitation frequency. However, such an approach neglects the inherently kinetic nature of the glass transition and may obscure thermally induced changes in relaxation response. Multi-frequency DMTA was employed to investigate the evolution of glass transition response of a wet-layup unidirectional carbon/epoxy composite subjected to thermal aging at temperatures ranging from 66 °C to 260 °C for periods up to 72 h, using unexposed (23 °C) results as an ambient baseline reference. Tests were conducted using a single cantilever mode in both longitudinal and transverse configurations over a range of excitation frequencies from 0.3 to 30 Hz. Results demonstrate that thermal exposure affects not only the absolute value of the glass transition temperature, but also its frequency sensitivity and directional dependence. A frequency sensitivity parameter and a directional amplification factor are introduced to quantify frequency–direction coupling. While post-cure-dominated aging regimes exhibit relatively stable coupling behavior, degradation-dominated conditions at elevated temperatures and longer periods of thermal exposure lead to pronounced increases in transverse frequency sensitivity, which reflects early evolution of matrix- and interphase-level deterioration. These findings highlight the value of multi-frequency DMTA with tests in both primary directions for the mechanistic assessment of effects of thermo-oxidative response in polymer matrix composites. Full article

Fast-curing polyurethane (PU) systems are attractive for high-throughput manufacturing, but quantifying cure kinetics, gelation, and cure-dependent glass transition temperature ($T_g$) is difficult, especially at a low degree of cure (DoC). Here, a fast-reacting BASF PU formulation was studied using non-isothermal differential scanning calorimetry (DSC) at multiple heating rates, rheometry at 50 °C, and molecular dynamics (MD) simulations to extend $T_g\left(\alpha \right)$in the low-DoC regime. DSC provided reaction enthalpy and conversion histories, and Kamal–Sourour (KS) parameters were identified by robust nonlinear fitting, reproducing conversion and curing rate profiles (R² > 0.99 and >0.95). Rheology indicated gelation between 475 and 625 s (DoC ≈ 0.53), and DSC-based $T_g$ at uncured, gelation, and fully cured states, established the experimental $T_g$ trend. MD (LAMMPS) with topological crosslinking and NPT thermal scans extracted $T_g$from density–temperature slopes at selected DoC points. Experimental and MD $T_g$ data were fused with Gaussian process regression constrained by the DiBenedetto relationship (5-fold cross-validation), giving λ ≈ 0.29 and confidence intervals. This framework links kinetics, gelation, and $T_g$ evolution for fast-curing PU and identifies the low-DoC region as the main source of uncertainty. Full article

Standard maturity methods for concrete monitoring rely primarily on temperature history, often neglecting the influence of internal relative humidity (RH) on hydration kinetics and self-desiccation risks. Continuous in situ monitoring of internal RH remains a challenge due to the high cost, proprietary nature, and lack of reproducibility of existing solutions. This study evaluates a low-cost, open-source embedded sensor array designed to characterize early-age curing behavior through trend-based monitoring—defined here as the evaluation of ensemble consistency and repeatability rather than absolute metrological traceability. The prototype system, based on SHT31 sensors controlled by an ESP32 microcontroller, was embedded in high-performance concrete cylinders (f′c = 45 MPa) to capture the exothermic hydration peak and the equilibration of internal humidity. Results demonstrate that while the sensor encapsulation introduced a geometric disturbance that reduced compressive strength by approximately 25%—a limitation requiring mitigation in structural applications—the system successfully captured reproducible curing transitions. The proposed framework provides an accessible tool for experimental research into internal curing conditions, offering a digital complement to traditional surface-based quality control. Full article

Octa(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane (8F-POSS) was synthesized via a vertex-capping method and incorporated into natural rubber (NR) and deproteinized natural rubber (DPNR) to fabricate inorganic–organic vulcanizates. Curing characteristics, crosslink density, and the filler–rubber interaction parameter (α) were evaluated. We found that 8F-POSS retarded vulcanization kinetics but eventually enhanced network integrity. Two-dimensional infrared (2D-IR) spectroscopy indicated a hydrogen-bond shielding effect between siloxane cages and protein hydroxyl groups in NR. This interaction governed morphology development: proteins in NR acted as compatibilizers to improve initial POSS dispersion, though at high loadings they compromised reinforcement efficiency (α fell from 18.12 to 9.04). In contrast, DPNR vulcanizates showed stronger direct filler–rubber interactions, with higher α values (25.66–35.58) and a more constrained physical network. Despite a denser physical network, the 8F-POSS cages increased fractional free volume and promoted interfacial frictional slippage, leading to a synergistic “reinforcement–dissipation” effect. As a consequence, 8F-POSS/DPNR vulcanizates exhibited an enhanced damping performance (e.g., a loss factor of 1.26) alongside a depressed Tg, reduced equilibrium swelling in oil from 324% to 147%, high hydrophobicity (water contact angle above 120°), and distinctive multi-stage thermal stability. These findings demonstrate a strategy to manipulate the protein network in NR using nanoscale hybrid fillers for the design of high-performance vulcanizates. Full article

Carbon-fiber-reinforced polymer (CFRP) composites possess outstanding specific stiffness and strength but typically exhibit low intrinsic damping, which limits vibration attenuation in lightweight dynamic structures. Herein, a hybrid toughening strategy combining carboxyl-terminated butadiene nitrile rubber (CTBN) and hexagonal boron nitride (h-BN) is developed to enhance the damping of CFRP laminates while preserving cure feasibility and thermomechanical stability. An E51/DICY/accelerator epoxy system (100:6.5:1.2, mass ratio) is used as the baseline matrix. Differential scanning calorimetry shows that both CTBN and h-BN shift the cure peak temperature upward (Tp: 160.6 → 170.3 °C) and reduce the reaction enthalpy (ΔH: 386.5 → 255.1 J/g), indicating dilution/transport effects and altered cure kinetics. Dynamic mechanical analysis (DMA) reveals that CTBN exhibits an optimum damping enhancement at 25 phr (tan δ_max = 0.300), whereas h-BN provides a stronger monotonic increase up to 25 phr (tan δ_max = 0.437). Notably, the CTBN/h-BN hybrid (25/25 phr) delivers a high tan δ_max of 0.468 together with the broadest effective damping window (ΔT_half = 28.6 °C), exceeding 85% of the linear additivity criterion proposed herein. When the materials are transferred into CFRP laminates, free-vibration tests (using the logarithmic decrement method) demonstrate a clear structural damping improvement (ζ: 0.021 → 0.035; δ: 0.132 → 0.221; t₁/₂: 0.48 → 0.27 s). Overall, the results suggest that the damping enhancement arises from a combination of EPBN-mediated ductile energy dissipation and h-BN-related interfacial/interlayer frictional losses, which can be jointly tuned to balance processability, thermal response, and damping performance in CFRPs. Full article