Curing Process Research Articles

Potassium Ion-Selective Electrodes with BME-44 Ionophores Covalently Attached to Condensation-Cured Silicone Membranes.

For ion-selective electrodes (ISEs) to be employed in wearable and implantable applications, the ion-selective membrane components should be biocompatible, and leaching of components, such as plasticizer or ionophore, out of the sensing membrane should be inhibited. To achieve this, we employed a plasticizer-free silicone as the membrane matrix and synthesized as the ionophore a derivative of the bis-crown ether based potassium ionophore BME-44, incorporating a triethoxysilyl functional group that covalently attaches to condensation-cured silicones during the curing process. Soxhlet extraction of these membranes with dichloromethane shows that up to 96% of the ionophore is attached to the silicone membrane during curing. We found that the covalently attachable BME-44 derivative can inadvertently adsorb onto high surface area carbon solid contacts before attaching to the silicone matrix if the curing of the silicone is performed in the presence of the high surface area carbon, resulting in depletion of ionophore from the membrane and yielding solid-contact ISEs with poor selectivity. In contrast, we observed Nernstian responses to K+ in plasticizer-free silicone-based K+ ISMs with either mobile BME-44 or the covalently attachable BME-44 derivative when the membranes were prepared on octane-thiol coated gold electrodes, where ionophore adsorption does not occur to a noticeable extent. As compared with ISMs doped with the mobile BME-44, ISMs prepared with the covalently attachable BME-44 derivative have better selectivity for K+ vs Na+ ( values of -3.54 and <- 4.05 for mobile and covalently attachable BME-44, respectively) and lower resistance. This can be explained by a more homogeneous incorporation of the covalently attachable BME-44 derivative into the silicone matrix than is the case for the mobile BME-44.

Study on mechanical properties and curing properties of shear‐thickening gel toughened epoxy resin

AbstractThe shear‐thickening gel (STG) is introduced as a toughening agent into the epoxy resin (EP) to improve the toughness and impact resistance of the EP without significantly increasing its viscosity. By utilizing the unique BO dynamic bonds present in STG, the EP/STG composite exhibits remarkable toughness at low strain rates due to the gradual disentanglement of molecular chains. Conversely, at high strain rates, the disentanglement of molecular chains is hindered, resulting in a pronounced impact hardening effect and overall superior impact resistance. Our findings reveal that when STG is added at a concentration of 15%, the EP/STG composite material attains its peak mechanical performance. Specifically, it demonstrates a tensile strength of 31.8 MPa and a modulus of elasticity of 550.6 MPa. Furthermore, compared to pure EP, the EP/STG composite experiences an increase in elongation at break and impact strength by 40% and 8.1%, respectively. Additionally, the introduction of hydroxyl and B atoms in STG promotes the ring‐opening reaction of epoxy groups during the curing process of the EP, thus accelerating the curing reaction rate. These insights provide a solid theoretical foundation for optimizing the performance of EPs in engineering applications.Highlights The STG was actively utilized to enhance the toughness of EP. The modified EP system exhibits significant improvements in toughness and impact resistance without a notable increase in viscosity. The promotional effect of STG on the curing of EP systems was revealed through curing kinetics analysis and rheological analysis.

Exploring the curing kinetics of Acrolein-Pentaerythritol resin: Impact of molecular weight and molecular weight distribution on cure behavior

Curing kinetics are crucial for designing and optimizing the process parameters of a resin. This study examines the non-isothermal curing kinetics of acrolein-pentaerythritol (APE) resins, focusing on the impact of molecular weight (MW) and molecular weight distribution (MWD) on their cure behavior. Kinetic parameters were determined using isoconversional and combined kinetic analysis methods through microcalorimeter measurements. The findings suggest that the cure process follows the nucleation and growth models (Avrami−Erofeev equation), with an activation energy of 72.2 kJ/mol. A comparison of two APE resins with different molecular weights and molecular weight distributions reveals that higher MW components expedite the initial curing reaction but impede the main curing process, leading to extended curing durations. This study provides valuable insights into the curing kinetics of APE resin and the influence of MW and MWD, contributing to the reliable and reproducible production of composite parts.

Enhancing epoxy composite materials through lime‐treated sugarcane bagasse and glass fiber reinforcement: Morphological, mechanical, and flame‐retardant insights

AbstractThis study investigates the utilization of sugarcane bagasse and glass fiber to reinforce epoxy composites, enhancing both mechanical and fire resistance properties. Initially, bagasse is collected, sun‐dried, and finely ground before being treated with lime water at concentrations of 3%, 5%, and 7% by weight. The treated bagasse is then mixed with epoxy resin and a hardening agent, followed by a curing process. For samples incorporating glass fibers, the fibers are manually integrated and cured similarly. The methodology involved detailed preparation of the bagasse, its treatment, and subsequent integration with epoxy resin. The mixture was processed under controlled conditions to ensure uniformity and quality. Mechanical properties such as tensile strength, flexural strength, compressive strength, and impact resistance were measured. Thermogravimetric analysis (TGA) was employed to assess thermal stability, while fire resistance was evaluated using the limiting oxygen index (LOI) and the 94‐V test method. Results demonstrated significant improvements in both mechanical and thermal properties with the addition of bagasse and glass fibers. The optimal treatment was identified at a 5% lime water concentration, yielding a tensile strength of 295.08 MPa, flexural strength of 371.24 MPa, compressive strength of 255.39 MPa, and Izod impact strength of 157.04 kJ/m2. TGA results showed the highest thermal stability at 5% concentration, with decomposition temperatures peaking at 402.52 °C. Fire resistance was markedly enhanced, achieving an LOI of 29.8% and meeting V2 level standards according to the 94‐V test method. In conclusion, treating sugarcane bagasse with a 5% lime water solution significantly enhances the mechanical and fire‐resistant properties of epoxy composites. The combination of sugarcane bagasse and glass fiber creates a robust material with high thermal stability and fire resistance, making it a viable option for applications requiring these enhanced properties.

Performance of magnesium oxysulfate (MOS) cement prepared by MgCl2·6 H2O replacing MgSO4·7 H2O

Despite the influence of Cl- on the properties of cement-based materials, water containing Cl- is more convenient for manufacturing cement-based materials in special areas such as islands and reef construction, compared to fresh water. However, research on the effects of Cl- on the properties of magnesium oxysulfate (MOS) cement was limited. In this paper, MOS cement was prepared by replacing MgSO4·7 H2O with MgCl2·6 H2O to investigate the effect of Cl- on the evolution of MOS cement properties. The mechanical properties, water resistance, phase composition, and microstructure of MOS cement were analyzed. When the replacement rate of MgSO4·7 H2O with MgCl2·6 H2O reached 5 %, MOS cement achieved its highest compressive strength of 77.5 MPa after curing for 90 days, despite a reduction in flexural strength due to MgO hydration. After immersion in water, the trend of compressive strength change in MOS cement remained insensitive to increasing immersion time. During the curing process, Cl- facilitated the formation of hexagonal Mg(OH)2 by participating in the hydration products formation process of MOS cement. Hexagonal Mg(OH)2 contributed to matrix construction and became connected with the 5Mg(OH)2·MgSO4·7 H2O phase. Additionally, Cl- promoted the formation of the modified 5Mg(OH)2·MgSO4·7 H2O phase, known as Mg-S-O-H-Cl phase. After immersion in water, the Mg-S-O-H-Cl phase displayed stability, showcasing their capacity to maintain compressive strength relative stability despite adverse factors such as ions leaching (including Mg2+, SO42-, and Cl-) and the phase transformation of MgO.

Curing-dependent behaviors of sustainable alkali-activated fiber reinforced composite: Temperature and humidity effects

Despite alkali-activated fiber reinforced composite (AAFRC) attracting increasing attention due to the advantages of low-carbon and superior tensile performance, the curing-dependent behaviors in practical environments are lack of knowledge. This paper aims to fill this gap by comparably investigating the macro-mechanical properties and pore structures of AAFRC under the different temperatures of −5, 20, and 60 °C and humidities of 60 % and 95 % RH. The loss on ignition, scanning electronic microscope (SEM), and fourier transform infrared spectroscopy (FT-IR) tests were performed to decouple the influence mechanisms. The results showed that the high-temperature curing slightly decreased the tensile and compressive strength but increased the tensile strain capacity with the main reason of decreasing the matrix toughness by forming more micro-cracks. The low-temperature curing deteriorated both the strength and tensile strain capacity by hindering its geopolymerization reaction. A decrease in humidity during the curing process was unconducive to the mechanical strength and slightly affect the tensile strain capacity of AAFRC, which resulted from the loss of water impeded its reaction to proceed. The normalized energy consumption and carbon emission of the AAFRC cured under the standard curing decreased by 22.6 % and 70.2 % than the classic engineered cementitious composite (ECC-M45), respectively, showing great sustainability.

High Throughput Manufacturing of Highly Ordered Mesoporous Thin Film Oxides for Hybrid-Polymer Nanocomposite Dielectrics

Highly ordered mesoporous metal oxide thin films have potential to become integrated into widely impactful dielectric materials due to the tunable properties of the oxide and its polymer filling; however, current manufacturing techniques to form the mesoporous oxide greatly limit scalable fabrication. Sol-gel mesoporous metal oxides generated via traditional processes require multi-day aging and high temperature, prolonged curing processes to yield controlled porosity at the expense of manufacturability. Moreover, high cost and unstable alkoxide precursors require precision over the solution precursor pH and subsequent thin film aging humidity after deposition.Solution combustion synthesis (SCS) is a next-generation method of generating metal oxides at reduced process temperatures (often <300 ºC) and using green precursors compared to the sol-gel approach. The metal oxide is typically produced from a metal nitrate, which provides both the metal cation and oxidant and an organic chelator fuel. The fuel acts to stabilize the cation against hydrolysis and to participate in the exothermic redox reaction that results in the metal oxide.Here, we present porogen integrated rapid oxidation (PIRO) which utilizes the principles of SCS to fabricate large-area mesoporous thin films of AlOx in less than 1 hour and at a temperature of 230 ºC. The PIRO method uses low-cost precursors to generate micelles with a controllable open-cell porosity ranging from ~30 – 60% and with varying degrees of closed-packed cubic ordering at a nearly 95% reduction in overall processing time. We show the precursor chemistry can be deposited via ultrasonic spray or blade coating at up to 6 m/min to manufacture large area mesoporous oxides and demonstrate filling of the porous AlOx with TOPAS® polymer to generate a hybrid nanocomposite with a dielectric constant of 6.26.

Thermal/photothermal-induced flexible folding and rapid soft-to-rigid transition in dark fiber composite structural components

Foldable and deployable structures find extensive applications in space deployment equipment, yet dark fiber composites (DFCs) utilized for crafting these structures still grapple with the trade-offs among resin flow, curing speed, and degree of cure. To address these issues, a novel thermal/photothermal (TPT) system was developed, leveraging two-stage and photo-induced photothermal synergistic techniques. The first stage involves a room-temperature click reaction, producing a gel intermediate state with an impressive fracture elongation rate of up to 123.15 %, allowing for arbitrary flexible folding and deployment. The second stage involves photo-induced photothermal curing, where the heat generated during the curing process (reaching temperatures up to 131.5 °C) can trigger thermal curing. The second-stage sample can achieve a Young's modulus up to 22,000 times that of the first stage. When applied in the fabrication of DFCs, the TPT system significantly enhances the curing degree of the resin on the backside of the DFCs, achieving a rapid soft-to-rigid transformation within 1 min. This represents a significant improvement over thermal curing in terms of speed and energy consumption. The use of DFCs in structural components has demonstrated their capability for flexible folding and rapid soft-to-rigid transformation.

The effect of absorbed moisture and resin pressure on porosity in autoclave cured epoxy resin

AbstractOne of the main issues in epoxy‐based composite manufacturing is the formation of porosity derived from moisture absorption during storage and layup due to the high hydrophilicity of epoxy matrices. During the curing process, the presence of moisture and other volatile compounds can initiate the nucleation and growth of voids. In this study, the effect of both the initial water content absorbed in the uncured resin and the pressure on the porosity development in an epoxy resin was investigated. In particular, Kardos' and Ledru's models, aimed at predicting void formation in polymers, were applied to study the effect of different hydrostatic pressures in an epoxy resin during curing up to the gel point, after conditioning it at two different relative humidity levels, 50% and 95%. Subsequently, the porosity of the cured resin samples was quantified through density measurements. Comparative analysis of the microscopy images of cured samples and the predictions of both models revealed an overestimation of the final void sizes by both models, with the Kardos' model exhibiting a higher deviation. Additionally, a finite element model was employed to investigate the conditions leading to void formation, aiming to understand the factors influencing the porosity development and properly set the process parameters during composite manufacturing.Highlights Evaluation of the conditions leading to void growth in epoxy resin during curing Moisture sorption in uncured epoxy resin Effect of curing pressure on pore development Finite element analysis for void growth during resin curing

Monoclonal Antibody Delivery Using 3D Printed Biobased Hollow μNe3dle Arrays for the Treatment of Osteoporosis.

Transdermal microneedles have demonstrated promising potential as an alternative to typical drug administration routes for the treatment of various diseases. As microneedles offer lower administration burden with enhanced patient adherence and reduced ecological footprint, there is a need for further exploitation of microneedle devices. One of the main objectives of this work was to initially develop an innovative biobased photocurable resin with high biobased carbon content comprising isobornyl acrylate (IBA) and pentaerythritol tetraacrylate blends (50:50 wt/wt). The optimization of the printing and curing process resulted in μNe3dle arrays with durable mechanical properties and piercing capacity. Another objective of the work was to employ the 3D printed hollow μNe3dles for the treatment of osteoporosis in vivo. The 3D printed μNe3dle arrays were used to administer denosumab (Dmab), a monoclonal antibody, to osteoporotic mice, and the serum concentrations of critical bone minerals were monitored for six months to assess recovery. It was found that the Dmab administered by the 3D printed μNe3dles showed fast in vitro rates and induced an enhanced therapeutic effect in restoring bone-related minerals compared to subcutaneous injections. The findings of this study introduce a novel green approach with a low ecological footprint for 3D printing of biobased μNe3dles, which can be tailored to improve clinical outcomes and patient compliance for chronic diseases.

A Study of Hydroxyl-Terminated Block Copolyether-Based Binder Curing Kinetics.

In order to determine the curing reaction model and corresponding parameters of hydroxyl-terminated block copolyether (HTPE) and provide a theoretical reference for its practical application, the non-isothermal differential scanning calorimetry (DSC) method was used to analyze the curing processes of three curing systems with HTPE and N-100 (an aliphatic polyisocyanate curing agent), isophorone diisocyanate (IPDI), and a mixture of N-100 and IPDI as curing agents. The results show that the curing activation energy of N-100 and HTPE was about 69.37 kJ/mol, slightly lower than the curing activation energy of IPDI and HTPE (75.60 kJ/mol), and the curing activation energy of the mixed curing agent and HTPE was 69.79 kJ/mol. The curing process of HTPE conformed to the autocatalytic reaction model. The non-catalytic reaction order (n) of N-100 and HTPE was about 1.2, and the autocatalytic order (m) was about 0.3, both lower than those of IPDI and HTPE. The reaction kinetics parameters of the N-100 and IPDI mixed curing agent with HTPE were close to those of N-100 and HTPE. The verification results indicate a high degree of overlap between the experimental data and the calculated data.

Curing kinetics and mechanical properties of the epoxy vitrimer based on transesterification and its composite laminates

AbstractThe resin is a fundamental factor in determining the performance and usage conditions of its composites. The epoxy vitrimer, which combines both thermoplastic and thermosetting properties, shows significant potential in extending the service life of material. The curing process significantly affects the macroscopic properties of the vitrimer and the resulting carbon fiber reinforced plastics (CFRP). Effective control of curing parameters constitutes the critical factor for the assurance of product quality. In the study, a differential scanning calorimetry (DSC) was utilized to establish a curing kinetics model for a modified, self‐healable epoxy vitrimer based on transesterification. Then the molecular structure, thermodynamic, and mechanical properties of the cured vitrimer were analyzed. Next vitrimeric CFRP (vCFRP) laminates were fabricated, and the tensile and bending properties of the vCFRP laminates were investigated. The results showed the curing process was obtained: 95°C/1 h + 150°C/2 h + 170°C/2 h. The thermodynamic and mechanical properties of cured vitrimer could meet practical requirements. The minimal differences observed in the stress–strain curves of the specimens indicated that the curing process was appropriately configured. The prepared laminates exhibited performance comparable to that of commercial thermosetting composites.

Experimental Assessment of Hemp Shiv and Green Adhesives to Produce a Biocomposite Material.

This study investigated the utilization of innovative green composites made from hemp shiv, a waste by-product of hemp cultivation, with the aim of promoting sustainability within the construction industry. The manufacturing method involved the application of pressure in a mold to create the samples. These materials were produced using an environmentally friendly binder consisting of colophony, arabic gum, and corn starch. Moreover, white glue and bioepoxy were also used to compare with the green resins. Three different binder compositions were used for the specimens. The samples underwent mechanical testing through tensile and bending assessments, and their performance was compared to that of non-green binders to validate the effectiveness of the manufacturing processes. The study revealed that decreasing the moisture content during the curing process was crucial for improving the mechanical properties. The best results were achieved when using arabic gum as a binder, yielding a tensile strength of 2.16 MPa and a bending strength of 5.25 MPa, with a composition of 62.5% hemp shiv and a manufacturing process involving a pressure of 5 MPa.

Exploring anti-corrosion properties and rheological behaviour of tannic acid and epoxidized soybean oil-based fully bio-based epoxy thermoset resins

This research explores the physicochemical attributes of a fully bio-epoxy thermoset aimed at serving as an anti-corrosion coating for safeguarding carbon steel structures in marine environments. Throughout this investigation, various epoxy thermosets formulations, based on epoxidized soybean oil (ESO) and tannic acid (TA), were synthesized by adjusting the initial ratios of epoxide:hydroxyl groups (epoxy:OH). These formulations were subsequently applied onto carbon steel substrates and subjected to thermal curing at moderate temperatures (170 °C) to evaluate their anti-corrosion effectiveness using electrochemical impedance spectroscopy (EIS). The examination of the total impedance values derived from EIS Bode diagrams (>106 Ω) revealed a notable anti-corrosion efficacy that endured over several months of immersion in 3.5 wt% NaCl solutions. In addition to electrochemical assessment, a rheological analysis was conducted to determine the optimal curing temperature for each formulation and to track the evolution of their mechanical properties throughout the curing process. Furthermore, the progression of corrosion at the coating-metal interphase was quantified using samples featuring artificially created notches to facilitate rapid water penetration, reaching the protected surface. Moreover, cross-cut and pull-off adhesion tests were conducted on coatings cured with various epoxide:hydroxyl ratios, yielding exceptional results on carbon steel substrates. Overall, a great potential for anti-corrosion protection has been demonstrated on the developed fully bio-based coatings with tuneable mechanical properties, regarding the initial component ratio, to reach the specific requirements for specific applications.

Biomimetic 3D printed spicule-like structure composite of organic material/rigid resin cylinders with highly enhanced strength and toughness

Recently, the microstructure of Euplectella Aspergillum (EA) marine sponges, called spicule, has been recognized as one of the attractive biological microstructures with superior flexural strength and toughness. The lack of studies to mimic this structure motivated us to design rods with a spicule-inspired structure with improved mechanical properties. In this study, spicule-inspired structures were produced by the stereolithography (SLA) method. Different adhesives were infiltrated between the layers to evaluate the effect of organic materials on their mechanical properties. The effect of the curing process on the mechanical properties of spicule-inspired structures with and without organic (adhesive) interlayers was evaluated. Also, the effects of various adhesives, different spaces between the cylinders, and ultraviolet (UV) curing on mechanical properties were evaluated. The results showed that the flexural strength of spicule-inspired structures was improved by about 71 % after curing the samples at 60 °C and under UV light for 30 min and aging in the air for 30 days. Samples including Titebond adhesive (SP1-1.1) showed a higher amount of peak load (129.5 ± 17.21 N) and extension (22.3 ± 3.12 mm) compared to those counterparts without any organic layers (SP-1.1) with a peak load of 101.5 ± 13.34 N and extension of 19.1 ± 1.32 mm. Adding the adhesive layers between the rigid cylinders enhanced the flexibility and strength of the structures. It was found that the curing time by UV after 30 days of aging did not affect the mechanical properties of the samples.

Synthesis of a novel bio-based curing agent and the curing behavior of the corresponding epoxy asphalt system

Traditional epoxy asphalt is made from petroleum resources. However, petroleum-based materials may cause environmental pollution and are not renewable. In this study, a bio-based curing agent MYM was synthesized from Maleic anhydride and Myrcene. The cured epoxy EP/MYM with the weight ratio of 1:1 were prepared. When preparing the modified asphalt, carboxyl-terminated liquid nitrile butadiene rubber (CTBN) was incorporated into the EP/MYM system to obtain the EP/MYM/CTBN modified asphalt system (referred to EMC epoxy asphalt). Firstly, the chemical structure of MYM was characterized using Fourier transform infrared spectroscopy (FTIR). Secondly, the mechanical properties and thermal stability of the cured EP/MYM were investigated by tensile test and thermogravimetric analysis (TG). Thirdly, the novel EMC epoxy asphalt was prepared and its composition was optimized. The curing behavior of the EMC epoxy asphalt was investigated by differential scanning calorimetry (DSC). And the time-temperature-transition diagrams (TTT diagrams) were plotted to determine the optimal curing process. Then the surface micro-morphology of EMC epoxy asphalt was investigated by atomic force microscopy (AFM). Finally, the high-temperature viscoelastic properties of EMC epoxy asphalt were investigated using dynamic shear rheology (DSR) tests. The results showed that EP/MYM has better mechanical strength and more excellent flexibility than those of EP/MTHPA and EP/MHHPA. The weight ratio of EP:MYM:CTBN was 10:8:1.5, and the optimal amount of diluent was 8 % of the total weight of the modifier. The semi-empirical kinetic modes of curing reaction were used to plot the TTT diagram of EMC epoxy asphalt, thus determining its curing technique as 120℃/2 h+160℃/3 h. The cured EMC epoxy asphalt showed uniform alternation of light and dark areas in the AFM images, indicating good compatibility and stability. The high-temperature deformation resistance of EMC epoxy asphalt was significantly improved compared to the base asphalt. The novel epoxy asphalt system prepared in this research provides a new route for the development of echo-friendly epoxy asphalt.

Characterization of Sequential Trial‐Curable Off‐Stoichiometric Amine‐Epoxy Thermosets with Ionic Liquids

This work aims to develop sequential trial‐curable off‐stoichiometric thermosets, patterning the approach upon the dual‐curing processing, which is a promising method to tailor material properties by combining two polymerization reactions. The presented epoxy resin systems are based on diglycidyl ether of bisphenol A (DG) as an epoxy resin, Gaskamine 240 (G) as a low‐temperature amine curing agent, and 1‐ethyl‐3‐methylimidazolium dicyanamide (IL) as an ionic liquid, which is known by its potential efficient latency. Therefore, three curing polymerization reactions take place, in contrast to common dual‐curable formulations. In this study, the target is to still separate the first curing process – which is the epoxy‐amine condensation reaction – from the remaining two curing processes, which are triggered by IL. The trial‐curable systems offer the possibility to achieve different intermediate materials, from highly viscous through shape‐conformable to rigid. This is attained by changing the relative contribution of the first and the other two curing steps, e.g. the change in the amount of G. Another motivation to use IL is to enhance the glass transition temperature of final samples; the values are between 84.4 and 152.2 °C.

Wear Performance Evaluation of Polymer Overlays on Engine Bearings.

Modern engine bearing materials encounter the challenge of functioning under conditions of mixed lubrication, low viscosity oils, downsizing, start-stop engines, potentially leading to metal-to-metal contact and, subsequently, premature bearing failure. In this work, two types of polymer overlays were applied to the bearing surface to compensate for extreme conditions, such as excessive loads and mixed lubrication. Two different polymer overlays, created through a curing process on a conventional engine bearing surface with an approximate thickness of 13 µm, were investigated for their friction and wear resistances under a 30 N load using a pin-on-disc setup. The results indicate that the newly developed polymer overlay (NDP, PAI-based coating) surface has a coefficient of friction (COF) of 0.155 and a wear volume loss of 0.010 cm3. In contrast, the currently used polymer overlay (CPO) in this field shows higher values with a COF of 0.378 and a wear volume loss of 0.024 cm3, which is significantly greater than that of the NDP. It was found that, in addition to accurately selecting the ratios of solid lubricants, polymer resins, and wear-resistant hard particle additives (metal powders, metal oxides, carbides, etc.) within the polymer coating, the effective presence of a transfer film providing low friction on the counter surface also played a crucial role.

Development of alginate/chitosan hydrogel loaded with obestatin and evaluation of collagen type I, III, VEGF and TGF-β1 gene expression for skin repair in a rat model (in vitro and in vitro study).

Skin injuries have long been recognized as a prevalent type of physical injury. As a result, numerous research studies have been performed to discover an effective mechanism for wound healing. Therefore, tissue engineering of skin has developed as a potential solution for traditional methods of treating skin injuries. Alginate/Chitosan hydrogel was mixed with 1, 10, 100, and 150µM Obestatin, and evaluated the morphology, cumulative release, hemocompatibility and cytocompatibility, water absorption, cell viability, weight loss, and antibacterial characteristics of three-dimensional (3D) alginate (Alg) and chitosan (Cs) hydrogels during the process of wound curing. Various concentrations of Obestatin (Obes) were utilized for this purpose. Finally, the hydrogels that were made were tested on a full-thickness dermal wound in a Wistar rat model. The curative effects were determined by analyzing RNA expression and examining tissue stained with Masson's trichrome (MT) and hematoxylin-eosin (H&E). The biodegradability of this hydrogel was verified using weight loss testing, which demonstrated a reduction of around 90% after a period of 3 days. Furthermore, the MTT assay demonstrated that hydrogels have a beneficial effect on cell proliferation without inducing any harmful effects. Furthermore, the hydrogels produced demonstrated higher wound closure in vivo compared to the wounds treated with gauze (negative control group). Among the hydrogel groups, the chitosan/alginate/obestatin 100µM group exhibited the apical percentage of wound closure, gene expression, and secondary epithelialization, but in 150µM concentrations, we saw a lower rate of cell growth and proliferation and increase in hemolysis. In addition, RT-PCR analysis demonstrated that a concentration of 100µM obestatin resulted in an upregulation in the expression of mRNA for vascular endothelial growth factor (VEGF), collagen type I & type III, and transforming growth factor-beta (TGF-β). The present study suggests that 3D Alg/Cs hydrogels with a concentration of 100µM obestatin have the potential for clinical application in the treatment of skin injuries.

Mechanical properties of cement-based composites incorporating eco-friendly aggregate of waste rubber

The purpose of this study is to evaluate the waste tires that harm the environment as aggregate in concrete and to examine the effect on the mechanical properties of concrete. Three different classes (powder, crumb and chips) of waste rubber with seven different ratios (0%, 4%, 8%, 12%, 16%, 20% and 24%) and two different water to cement ratio (0.4 and 0.5) were used in concrete production. In this regard, this study conducted various experiments consisting of 28 and 90 days of the curing process to determine the properties of unit weight, compressive, flexural, and splitting tensile strength, along with ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity. The waste rubber concrete with the highest compressive strength at the end of 90 days is the concrete that includes 4% waste rubber (0.4WR4) with 58.81 MPa. Concrete containing 8% waste rubber has the highest UPV of 5660 m/s after 90 days. The increase in the water/cement ratio from 0.4 to 0.5 and the waste rubber ratio cause deterioration in the mechanical properties of concrete. Although the use of waste rubbers does not bring an increase in strength, it is feasible to produce high strength concretes with 4% and 8% waste rubber substitution ratios. The water/cement ratio and curing time were highly effective on the mechanical properties of rubberized concrete.