Curing System Research Articles

Establishment of 3D Cultures of Myometrium, Leiomyoma, and Leiomyosarcoma Cells: Advantages and Disadvantages of Two Different Models.

Uterine leiomyomas are the most common benign, monoclonal, gynaecological tumors in a woman's uterus, while leiomyosarcoma is a rare but aggressive condition caused by the malignant transformation of the myometrium. To overcome the common obstacles related to the methods usually used to study these pathologies, we aimed to devise three-dimensional models of myometrium, uterine leiomyoma and leiomyosarcoma cell lines, using two different types of biocompatible scaffolds. Specifically, we exploited the agarose gel matrix in common 6-well plates and the alginate matrix using Bioprinting INKREDIBLE + (CELLINK), a pneumatic extruded base equipped with a system with double printheads, and a UV printer LED curing system. Both methods allowed the development of 3D spheroids of all three cell types, that were also suitable for morphological investigations. We showed that all cell types embedded in both agarose and alginate formed spheroids in their growth medium. The spheroids successfully proliferated and self-organized into complex structures, developing a sustainable system that emulated the condition of the tissues through the accumulation of extracellular matrix. These models could be useful for a better understanding of pathophysiology, etiopathogenesis, and testing new methods or molecules from a preventive and therapeutic point of view.

Synergistic effects of tertiary amine and imidazole accelerators on epoxy resin curing

AbstarctIn order to improve the curing rate, this study investigated the influence of various accelerators and their combinations on the curing behavior of epoxy resins. differential scanning calorimetry (DSC) was used to analyze the curing behavior of various accelerators in diglycidyl ether of the bisphenol A epoxy resin and the methyl hexahydrophthalic anhydride curing system, and activation energies were calculated using the Kissinger and Ozawa models. The results indicated a self‐catalytic characteristic in the curing process and showed that the activation energies for tris(dimethylaminomethyl)phenol (DMP‐30) and 1‐cyano‐2‐ethyl‐4‐methylimidazole (2E4MZ‐CN) were significantly lower compared to N,N‐dimethylbenzylamine, demonstrating higher curing reactivity. Furthermore, a novel strategy combining tertiary amine accelerator (DMP‐30) and imidazole accelerator (2E4MZ‐CN) was proposed and the activation energy variations with the degree of cure were analyzed employing the KAS method. When the mass ratio of DMP‐30 to 2E4MZ‐CN was 1:3, the activation energy was 59.08 kJ/mol, approximately 12% lower than using a single accelerator, which indicated the synergistic effects of the accelerators. Finally, the mechanism of synergistic effect of tertiary amine and imidazole accelerators on epoxy resin curing were proposed.

Analysis of bio-based epoxy resins: Impact of amine hardeners on thermal, thermomechanical, optical and electrical properties of epoxidized resveratrol with high Tg

Epoxidized resveratrol (RES) has been cured with different amines in order to compare their possibilities to obtain high-temperature resistance of bio-based epoxy resins. Materials obtained from the bio-based monomer present glass transition temperatures (Tg) among the highest ever reported for an epoxy-amine curing system, with extremely high char residue, making them excellent candidates for extremely high-temperature applications. Particularly, epoxidized RES stoichiometrically cured with 4,4′-sulfonyldianiline (DDS) reached 297 °C, measured as the tan δ peak by DMTA, and two other materials, using 4,4′-methylenedianiline (DDM) and 4,4′-diaminodicyclohexylmethane (CAA) as curing agents, exceeded 300 °C. In fact, the material begins to degrade before the chains are fully relaxed, so they are thermosetting that never go completely into the rubbery state. Additionally, this resin improves the direct current (DC) insulating character (~1015 Ωcm) while decreasing the optical band gap (~2 eV) when compared to other epoxy resins available, which is of great interest for photovoltaic applications. Moreover, some of the materials presented a very high char residue proportion when heated (>40 wt% at 800 °C under nitrogen atmosphere), presenting good fire-retardant properties.

A Comparative Study on the Behaviour of Various Methods of Curing Concrete

Abstract: The properties of cement-based products, especially their durability, are predominantly influenced by curing, since it has a remarkable effect on the hydration of the cement. Proper curing of cement-based products is crucial to obtaining design strength and maximum durability. The curing period depends on the type of cement works, the purpose for which it is to be used and the surrounding atmosphere, namely temperature and relative humidity. Curing is designed primarily to maintain the moisture, by avoiding the loss of moisture from the period in which it is gaining strength. Curing may be applied in a number of different processes and the mass appropriate means of curing may be directed by the site or the construction method. In this critique, a paper struggle has been made to understand the working and efficiency of curing system which are generally adopted in the construction industry and compared with the standard water curing method.

Preparation and Electrical Properties of Nanocomposite Based on Epoxy Resin and Core-Shell Polyaniline/Multi-Walled Carbon Nanotubes

Nanocomposites of epoxy resin containing various concentrations of carboxylated multiwalled carbon nanotubes (C-MWCNTs) and surface modified C-MWCNTs various concentration of both C-MWCNTs and core-shell nanoparticles were prepared. The physical, mechanical and electrical properties of prepared epoxy nanocomposites were investigated using experimental evaluations such as dynamic mechanical thermal analysis (DMTA), differential scanning calorimeter (DSC), and tensile strength measurements. The results of DSC tests revealed that the introduction of nanoparticles into the epoxy resin did not have much effect on the curing system, and by adding these nanoparticles to the epoxy resin, there is no need to change the curing system. However, the released energy during of epoxy curing show a 24% increase with the introduction of nanofiller into the epoxy matrix. The results of electrical conductivity measurements indicated a higher elastic dielectric constant for nanocomposites up to 200% incomparison with neat epoxy resin. The use of these epoxy nanocomposites in modern electrical and electro-optical industries is of great practical importance.

Poly(lactide) Upcycling Approach through Transesterification for Stereolithography 3D Printing.

The legislature determines the recycled and waste contents in fabrication processes to ensure more sustainable production. PLA's mechanical recycling and reuse are limited due to the performance decrease caused by thermal or hydrolytic instability. Our concept introduces an upcycling route involving PLA depolymerization using propylene glycol as a reactant, followed by the methacrylation, assuring the liquid systems' curability provided by radical polymerization. PLA-containing curable systems were studied from a rheological and thermomechanical viewpoint. The viscosity levels varied from 33 to 3911 mPa·s at 30 °C, giving a wide capability potential. The best system reached 2240 MPa storage modulus, 164.1 °C glass-transition temperature, and 145.6 °C heat-resistant index, competitive values to commercial systems. The printability was verified for all of the systems. Eventually, our concept led to SLA resin production containing PLA waste content up to 51 wt %.

Preparation of Imidazole Compounds as Latent Curing Agents and Their Application in RGB LED Packaging.

LED packaging miniaturization has raised more requirements for LED materials. As a material contacting the LED chip directly, the reliability of LED non-conductive adhesive has also garnered increasing attention. This study optimized the formula for non-conductive adhesives for an imidazole curing system. The optimized composition of the adhesive is 25%wt for the curing agent and 30%wt for the silica. The prepared non-conductive adhesive has a 7-day pot life and 9-month storage stability. The shear strength reached 87 g and 72 g at 25 °C and 160 °C, respectively. The reliability of the LED modules packaged with the non-conductive adhesive was researched. The green and blue light intensity change was 4.7%, 43.7%, respectively, indicating good anti-aging properties. The blue light decay was mainly due to adhesive aging. The non-conductive adhesive effectively prevented "caterpillar" growth. This provides useful and practical guidelines for industry for applications of adhesive in different packages.

Mechanical properties and durability of lightweight cenosphere cementitious composites under coupling effect of dry-wet cycles and salt erosion

Cenospheres are suitable as supplementary cementitious materials to partially replace cement in the production of environmentally friendly lightweight cenosphere cementitious composites (LCCC). In this study, the correlation between the content and particle size of the cenosphere, the early curing system and the performance of LCCC was analyzed. The macroscopic properties and microstructural changes of LCCC under the conditions of dry-wet cycles and salt erosion were studied with different early curing conditions. The durability changes of LCCC mortar under the coupling effect of salt erosion and dry-wet cycles were studied by examining the mass loss rate, relative dynamic modulus of elasticity and salt corrosion resistance coefficient of LCCC mortar. Finally, a comparative analysis of the impact of existing cracks on the performance of LCCC under the coupling effect of dry-wet and salt erosion was conducted. The main innovation of the study includes the mechanical properties and durability of LCCC under dry-wet-salt erosion conditions, as well as the clarification of the impact of prefabricated cracks on the mechanical properties and durability of LCCC. It is found that the flexural strength and the compressive strength of specimens cured at high temperature is generally lower than that of the specimens cured under normal temperature conditions. The wet-dry salt corrosion can exacerbate the erosion the outer shell and inner wall of cenospheres and disrupt the stability of the internal interface transition zone (ITZ) in LCCC. LCCC with CsS exhibits better macroscopic performance and microstructural properties. Pre-existing cracks accelerates the erosion in the cenosphere shell and inner wall under salt solution.

Comprehensive Utilization of Industry By-Products in Precast Concrete: A Critical Review from the Perspective of Physicochemical Characteristics of Solid Waste and Steam Curing Conditions

Solid wastes have been widely used as a cement substitute in precast concrete. On the one hand, solid waste can effectively ameliorate a series of problems caused by steam curing. On the other hand, the use of solid waste can reduce the amount of cement used in the construction industry and reduce carbon emissions. However, due to the complexity of the steam curing system, the performance of precast concrete prepared under different steam curing conditions varies greatly. Moreover, there are a wide variety of solid wastes, and the differences in the physicochemical properties of different solid wastes are significant. Therefore, it is necessary to systematically determine the mechanism of action of commonly used solid wastes. In this paper, the steam curing system is introduced in detail, and the mechanism of action of solid waste in precast concrete is systematically summarized. It was found that an appropriate increase in the temperature and duration of steam curing facilitates the strength development of precast concrete. In addition, there is a difference in the effect of the addition of solid wastes on the early and late strength of precast concrete, which usually leads to a decrease in the demolding strength of precast concrete, but increases the late strength of precast concrete. This study provides a reference for rationally regulating steam curing systems and realizing the comprehensive utilization of solid wastes in precast concrete.

Coupling antitoxins and blue/white screening with parAB/resolvase mutation as a strategy for Salmonella spp. plasmid curing.

Plasmids play an important role in bacterial physiology, adaptation, evolution, virulence, and antibiotic resistance. An in-depth study of these roles partly depends on the generation of plasmid-free cells. This study shows that vector tools that target genes required for plasmid stability in the presence of an antitoxin-expressing helper plasmid are a viable approach to cure specific plasmids. Expression of bgaB from target plasmids can greatly facilitate visual detection of plasmid cured colonies avoiding time-consuming screening procedures. This approach can be refined for the development of a universal plasmid curing system that can be used to generate plasmid-free cells in other human bacterial pathogens including Gram positives and Gram negatives.

Regulation of the Phase Structure in the Crystallizing Curing System PCL–DGEBA

Qualitative and quantitative aspects of the formation of various types of phase structures, sizes and compositions were considered. For the studied polycaprolactone–epoxy resin/4,4′-diaminediphenylsulfone system, a phase diagram characterized by amorphous separation with a lower critical solution temperature was constructed and its evolution was traced with increasing conversion degree of epoxy groups. A method is proposed for determining the temperature–concentration parameters that determine the type of phase structure of composite materials, based on the optical interferometry method. All types of phase structures and features of structure formation in the phase reversal region and at its boundaries have been studied using optical and scanning electron microscopy methods. The dimensions of the structural elements were determined and their correlation with the temperature and concentration regimes of the system’s curing was established. The composition of phases in cured compositions was studied using FTIR spectroscopy, DSC and scanning electron microscopy. It is shown that by varying the temperature–concentration parameters of curing reactive thermoplastic systems, it is possible to specifically regulate the type of phase structure, phase sizes and their composition, which determine the operational properties of the material.

Rational design of a room‐temperature curing method, based on the epoxy–thiol click reaction, for UV‐curable hard coatings with ultrahigh strength and adhesion

AbstractIn recent years, there has been a growing demand for UV‐curable hard coatings because they offer several advantages, for example, lower energy consumption and the absence of volatile organic compound emissions. Anionic UV curing with photobase generators (PBGs), such as epoxy–thiol cross‐linking, enables curing under ambient conditions. However, designing a room‐temperature photoanionic curing system for epoxy–thiols remains challenging due to the complex effects of resin combinations on the cured products, thus making it difficult to prepare films with high hardness. Herein, we present a controlled reaction design for an anionic UV‐curing system by combining the chemical structures of epoxy resins and multifunctional thiols. The anionic UV‐curing system using PBGs that generate organic superbases demonstrated UV‐delayed curability, as evidenced by FT‐IR and photorheological analyses. To achieve high hardness, it was necessary to create the thiols with ultrarigid structures; epoxy resins with a bisphenol F structure were optimal for reacting with thiols for ultrarigid structures. This combination afforded an indentation hardness of 262 MPa with an epoxy conversion rate of 77% even at room temperature.

Cure, mechanical and swelling characteristics of composites of neoprene rubber and starch from non-edible variety of dioscorea tuber

Composites of Polychloroprene rubber (CR, Neoprene rubber) reinforced with starch from non-edible variety of dioscorea tuber were prepared using three different vulcanizing systems. The cure, mechanical, solvent resistance and biodegradable characteristics of the composites were studied. The addition of starch from dioscorea tuber was found to improve CR’s tensile strength. The maximum torque value increases with the loading of filler and it was found to be the highest at 20 phr. The addition of starch from dioscorea tuber was found to improve CR’s tensile strength and highest value observed at 20 phr. Among the different curing systems studied, the modified DCP system shows maximum mechanical properties, optimum properties of the composites are at 20 phr. The values of the swelling coefficients were determined by examining the intake of the solvents N, N-dimethylformamide, acetonitrile, dimethyl sulfoxide and water by the composites. The soil burial test indicated that biodegradability of CR enhanced with the addition of starch. The findings of mechanical properties are supported by studies using scanning electron microscopy. Since starch is a naturally occurring biopolymer, adding it encourages microbial activity, which breaks down the composite components. This quality is essential for resolving plastic waste-related environmental issues. It is anticipated that the findings of this study will aid in the development of materials for specific product applications like gasoline hoses, tire sidewalls, seals, and so on.

Using nitrogen-containing organosilicon compounds in the creation of heat- and fire-resistant filling compositions to seal high-voltage and high-frequency equipment

Objectives. To study the possibility of using nitrogen-containing organosilicon compounds in the creation of heat-resistant and fireresistant casting compositions to seal high-voltage high-frequency equipment.Methods. Nitrogen-containing organosilicon compounds were obtained using the N-siloxycarbonylation, formylation, and silylation methods. The methods used in the work were infrared spectroscopy, elemental analysis, viscometry, and differential scanning calorimetry. The mechanical and dielectric properties of the samples were determined.Results. Previously unknown substances and compounds containing nitrogen-containing organosilicon products as components of the curing composition were obtained. Their physicomechanical and operational properties were examined, including the possibility of using them as filling heat-resistant and fire-resistant compositions for sealing high-voltage and high-frequency equipment.Conclusions. It was shown that nitrogen-containing organosilicon compounds — 3-(diethylamino)-2-[(triethoxysilyl)oxy]propyl-2-methacrylate and triethoxysilyl ester of γ-triethoxysilylpropyl-carbamic acid — can be used as part of a curing system together with bromine-containing fillers, in order to obtain compounds used for filling high-voltage high-frequency transformers, throttle valves, and other electronic equipment elements with non-combustible properties and increased heat resistance.

Polycaprolactone-based shape memory foams as self-fitting vaginal stents

There is an urgent critical need for a patient-forward vaginal stent that can prevent debilitating vaginal stenosis that occurs after pelvic radiation treatments and vaginal reconstruction. To this end, we developed a self-fitting vaginal stent based on a shape-memory polymer (SMP) foam that can assume a secondary, compressed shape for ease of deployment. Upon insertion, the change in temperature and hydration initiates foam expansion to shape fit to the individual patient and restore the lumen of the stent to allow egress of vaginal secretions. To achieve rapid actuation at physiological temperature, we investigated the effect of architecture of two photocurable, polycaprolactone (PCL) macromers. Star-PCL-tetraacrylate displayed a reduced melting temperature as compared to a linear-PCL-diacrylate. Upon fabrication into high porosity foams with emulsion-templating, both compositions displayed shape fixity (>90 %) in a crimped, temporary shape. However, only the PCL star-foams displayed shape recovery (∼84 %) at 37 °C with expansion back to its permanent shape. A custom mold and curing system were then used to fabricate the PCL star-foams into hollow, cylindrical stents. The stent was crimped to its temporary insertion shape (50 % reduction in diameter, OD ∼ 11 mm) with a custom radial crimper and displayed excellent shape fixity for deployment (> 95 %) and shape recovery (∼ 100 %). To screen vaginal stents, we developed a custom benchtop pelvic model that simulated vaginal anatomy, temperatures, and pressures with an associated computational model. The crimped SMP vaginal stent was deployed in the model and expanded to walls of the canal (∼70 % increase in cross-sectional area) in less than 5 min after irrigation with warm water. The vaginal stent demonstrated retention of vaginal caliber with less than 10 % decrease in cross-sectional area under physiological pressures. Collectively, this work demonstrates the potential for SMP foams as self-fitting vaginal stents to prevent stenosis and provides new open-source tools for the iterative design of other gynecological devices. Statement of significanceVaginal stenosis, a painful narrowing of the vaginal canal, is a common complication after pelvic radiation therapy or reconstructive surgery. To address this clinical need, we have created a self-fitting vaginal stent from a shape-memory polymer foam. The stent compresses for easy insertion and then expands to adapt to each patient's anatomy to maintain an open vaginal canal and prevent stenosis. This innovative stent provides a patient-friendly solution that could make a significant difference for women undergoing pelvic treatments by reducing pain, aiding recovery, and improving quality of life.

Effect of steam curing system on compressive strength of recycled aggregate concrete

Abstract Steam curing prefabrication is a feasible way to promote the application of recycled aggregate in the background of building industrialization. The combined use of slag and fly ash contributes to the comprehensive improvement of both the early and later-stage performance of recycled aggregate concrete (RAC). However, the steam curing regime for RAC composed of slag and fly ash remains unclear, including appropriate curing temperatures and time. In this study, the influences of curing temperatures (20, 40, 60, and 80°C), steam curing time (6, 9, and 12 h) and mineral admixtures (slag powder and fly ash) on the demoulding strength and strength development of RAC were investigated. Based on the Arrhenius formula, the hydration reaction rate was characterized by the development of compressive strength, the apparent activation energy related to the steam curing time was calculated, and the energy-based compressive strength model was proposed to realize the early strength prediction of the steam-cured RAC.

Preparation of low‐temperature curing single‐component epoxy adhesives with sedimentation coated accelerators

AbstractSingle‐component epoxy adhesives are widely used in various fields due to their simple operation process and excellent bonding properties. However, the excessively high curing temperature of the traditional single‐component epoxy adhesives may easily damage the electronic devices, limiting their further application. Hence, it is of great significance to develop the low‐temperature‐curing single‐component epoxy adhesives. However, the room temperature storage stability of low‐temperature curing system is generally poor. This work selected epoxy resin (EPON‐828), pentaerythritol tetra (3‐mercaptopropionate) (PETMP), 1‐benzylimidazole (1‐BMZ), and stabilizer (salicylic acid) as materials to prepare low‐temperature curing single‐component epoxy adhesives. In order to improve the storage stability of the system, polycarbonate (PCM‐A‐37) with low molecular weight was employed to coat the accelerator 1‐BMZ by physical sedimentation. The results showed that the room temperature storage period of the system reached 140 h, which was 2.18 times longer than before coating, and the curing temperature of 75°C was determined through DSC curves fitting. The epoxy adhesives have been completely cured at 75°C for 5 h, and shear strength reached 10.20 ± 0.51 MPa, which was not significantly different from that of the system with uncoated accelerators. We believe our paradigm can provide a feasible approach for preparing low‐temperature curing single‐component epoxy adhesives, and has reference significance for the preparation of single‐component adhesives in other systems, too.

A latent curing agent for rapid curing of phenolic epoxy resin at low temperature

AbstractDeveloping effective latent curing agent for rapid curing of epoxy resins at low temperatures remains challenging. This study reports a latent curing agent, ortho‐cresol phenolic epoxy resin‐bisphenol A (EOCN‐BPA), prepared through the addition reaction of o‐methyl phenolic epoxy resin with BPA. When blended with dicyandiamide (DICY) in a 1:3 molar ratio, EOCN‐BPA/DICY is used to cure a linear epoxy phenolic novolac (EPN) resin (epoxy equivalent: 550 g eq−1, softening point: approximately 82°C), at an onset curing temperature of 90°C, which is considerably lower than the onset curing temperature of DICY with EPN (160°C). However, EOCN‐BPA does not react with EPN without a catalyst. Therefore, this latent curing system is successfully applied in powder coatings, rapid curing at 120°C within 3 min without an additional catalyst, outperforming the EPN/EOCN‐BPA system using cocatalyst 2‐methylimidazole. Consequently, DICY catalyzes the curing reaction between the phenol hydroxyl group and epoxy resin and participates in it. The prepared powder coating exhibits excellent storage stability, maintaining its properties for over 3 months at room temperature. These findings demonstrate the excellent latent properties of EOCN‐BPA/DICY, highlighting its potential as a highly effective latent curing agent.

Introducing Diels‐Alder reaction with carbon nanotubes for the enhanced repair performance of epoxy resin modified asphalt

AbstractEpoxy asphalt, a thermosetting polymer, is characterized by stable, irreversible internal chemical bonds that prevent recovery and spontaneous micro‐crack healing, unlike conventional asphalt. This study introduces a renewable nano‐modifier synthesized via esterification of carboxyl‐functionalized carbon nanotubes (CNTs‐COOH) and furfuryl alcohol (FA), termed CNTs‐FA. The successful synthesis of CNTs‐FA was confirmed through various microscopic techniques. Integrating CNTs‐FA into epoxy asphalt materials, the optimal dosage was identified as 0.05% of the total epoxy asphalt mass using tensile tests and fluorescence microscopy. Thermal reversible effects and mechanisms were further analyzed through multiple regeneration cycles using tensile properties, fluorescence microscopy, and infrared spectroscopy. The study elucidates that the thermal reversibility in epoxy asphalt is facilitated by the Diels‐Alder (DA) reaction between the conjugated diene structure in FA and the curing agent oleylamine. This research provides an effective solution to the non‐recoverability and unrepairable micro‐cracks of traditional epoxy asphalt mixtures.Highlights CNTs‐FA was successfully prepared by esterification reaction. Using nano modification methods, introduce DA reaction into curing system. Renewable function of epoxy asphalt by DA reversible reaction.

Piezoresistive properties for soft structures using hybrid CCB/CNT-based natural rubber latex composites

This study explores the development of flexible sensors for soft structures. Conductive carbon black (CCB) and carbon nanotubes (CNT) were incorporated into a natural rubber (NR) matrix using glutaraldehyde (GA) as a curing system. The sensor properties of latex-NR composites with 20 phr of CCB, including variations of CNT content (0.5 to 3 phr), were examined. Increasing CNT content beyond 0.5 phr decreased tensile strength and elongation at break, but improved sensitivity and gauge factor (GF). Additionally, applying a voltage over 5 V caused a joule heating of the latex-NR composite strip elements. When integrated onto a soft tendon-based TPU bending actuator, higher CNT content reduced electrical signal drift during cyclic bending, enhancing long-term monitoring. This research highlights the potential of CCB/CNT-based latex-NR composites for soft structure applications, including soft robotics and health monitoring.