Ratio Of Curing Agent Research Articles

Effects of Polymer-Curing Agent Ratio on Rheological, Mechanical Properties and Chemical Characterization of Epoxy-Modified Cement Composite Grouting Materials.

This study designs and uses water-borne epoxy resin (WBER) and curing agent (CA) to modify traditional cement-based grouting for tunnels. The purpose of this paper is to analyze the rheological and mechanical properties of composite grouting with different ratios of WBER and CA and analyze the modification mechanism by means of chemical characterization to explore the feasibility of WBER as a high-performance modifier for tunnel construction. The composite grouting is prepared by mixing cement paste with polymer emulsion. A series of experiments was carried out to investigate the effects of WBER and CA, including the slump test, viscosity, rheological curve, setting time, bleeding rate, grain size distribution, zeta potential, compressive and splitting tensile strength, X-ray diffraction(XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), on the composite grout. The results show that WBER improves grout fluidity, which decreases in combination with CA, while also reducing the average particle size of the composite grout for a more rational size distribution. Optimal uniaxial (38.9%) and splitting tensile strength (48.7%) of the grout are achieved with a WBER to CA mass ratio of 2:1. WBER accelerates cement hydration, with the modification centered on the reaction between free Ca2+ and polymer-OH, significantly enhancing the strength, fluidity, and stability of the polymer-modified composite grout compared to traditional cement-based grouting.

Tailoring morphological and chemical contributions of nanoscale charge transfer for enhanced triboelectric nanogenerators.

Triboelectric devices, operating through contact electrification (CE) and electrostatic induction, have shown great promise in energy harvesting applications. However, optimizing charge transfer at the interface remains crucial for enhancing device performance. This study introduces a novel approach to harnessing CE by employing morphological and chemical modifications of polymers. Our strategy involves adjusting the elastomer base to curing agent ratio to fine-tune the chemical properties of polydimethylsiloxane (PDMS) and introducing morphological modifications through a peeling and flipping (P/F) process of PDMS off the Si-substrate. Unlike conventional methods, the P/F-method minimally alters the intrinsic properties of PDMS, creating nanoscale surface corrugations adiabatically. We explore the mechanical, tribological, and electrical properties of the surface at the nano-scale and demonstrate that our approach allows for precise control of energy dissipation and electric potential at the surface, thereby optimizing charge transfer. Furthermore, we show that using a plasma-treated Si-substrate can further increase device performance up to 80% without affecting other properties. This study presents a comprehensive strategy for fine-tuning CE to enhance the performance of triboelectric nanogenerators.

Rapid repair and degradation: A study of high-performance recyclable vitrimer epoxy resin based on disulfide bonds

Petroleum-based epoxy resin is commonly used in electrical equipment due to its outstanding performance and affordability. However, its non-melting characteristics present challenges for recycling, leading to significant resource waste and environmental pollution. To address this issue, this study prepared and synthesized a kind of vitrimer epoxy resin polymer material based on disulfide bonds with 2,2′-Diaminodiphenyl disulphide as the curing agent. The research investigated the impact of the curing agent ratio on the resin's structure and properties. The resin was mechanically recovered through hot pressing at high temperature and pressure, and its chemical degradation and recovery were achieved via the reduction reaction of the thiol and disulfide bond. The findings revealed that a curing agent to epoxy group material ratio of 0.75 improved the resin system's electrothermal properties. The electrical insulation property retention rate after hot pressing recovery reached 95 %, with a mechanical property retention rate of 85 %. The disulfide bonds can be reoxidized and crosslinked to realize the recovery and reuse of vitrimer resin degradation solution. Vitrimer epoxy resin based on disulfide bonds is a significant way to realize the environmental protection of epoxy electrical equipment.

Bone Fracture Healing under the Intervention of a Stretchable Ultrasound Array.

Ultrasound treatment has been recognized as an effective and noninvasive approach to promote fracture healing. However, traditional rigid ultrasound probe is bulky, requiring cumbersome manual operations and inducing unfavorable side effects when functioning, which precludes the wide application of ultrasound in bone fracture healing. Here, we report a stretchable ultrasound array for bone fracture healing, which features high-performance 1-3 piezoelectric composites as transducers, stretchable multilayered serpentine metal films in a bridge-island pattern as electrical interconnects, soft elastomeric membranes as encapsulations, and polydimethylsiloxane (PDMS) with low curing agent ratio as adhesive layers. The resulting ultrasound array offers the benefits of large stretchability for easy skin integration and effective affecting region for simple skin alignment with good electromechanical performance. Experimental investigations of the stretchable ultrasound array on the delayed union model in femoral shafts of rats show that the callus growth is more active in the second week of treatment and the fracture site is completely osseous healed in the sixth week of treatment. Various bone quality indicators (e.g., bone modulus, bone mineral density, bone tissue/total tissue volume, and trabecular bone thickness) could be enhanced with the intervention of a stretchable ultrasound array. Histological and immunohistochemical examinations indicate that ultrasound promotes osteoblast differentiation, bone formation, and remodeling by promoting the expression of osteopontin (OPN) and runt-related transcription factor 2 (RUNX2). This work provides an effective tool for bone fracture healing in a simple and convenient manner and creates engineering opportunities for applying ultrasound in medical applications.

Effect of curing agents n‐octylamine and m‐xylene diamine on the mechanical and memory properties of E51 epoxy resin

AbstractThe effects of curing agents n‐octylamine (OA) and m‐xylene diamine (MXDA) on the mechanical and memory properties of E51 epoxy resin (EP) are investigated in this work. The curing mechanism and thermal stability of OA and MXDA with EP are also investigated via Fourier‐transform infrared spectroscopy and thermogravimetric analysis, the influence of curing agent ratios on the thermo‐dynamic mechanical properties of EP are investigated through dynamic thermo‐mechanical analysis, and the relationship between the storage modulus, the hysteresis phase angle and the temperature are constructed. Moreover, the cross‐linking densities of the EP with different curing agent ratios are calculated using Archimedes's method. Besides, the effects of different proportions of curing agents on the mechanical properties of EP are studied. The results show that with the increases of MXDA ratio, the phase transition temperature, crosslink density, recovery temperature, recovery rate, the tensile strength, tensile modulus, strain strength, and strain modulus are enhanced, however, the hysteresis phase angle MXDA ratio and the tenacity decrease. Finally, the shape memory mechanism of E51 is discussed.

The effect of composite curing agent ratio on the photooxidative aging behavior of epoxy asphalt based on molecular dynamics simulation

In order to explore the effect of composite curing agent ratio on the photooxidative aging behavior of epoxy asphalt with an acidic composite curing system, three curing agent ratios of epoxy asphalt were prepared to obtain different cross-linking network densities. The prepared epoxy asphalt was subjected to photooxidation aging for 240 h at 60 ℃. Fourier transform infrared (FTIR) and elemental analysis tests were conducted to determine the evolution of chemical components during photooxidative aging. Based on the chemical components before and after aging, molecular models of photooxidation aged epoxy asphalt with different curing agent ratios were constructed. The mean square displacement (MSD) of oxygen atoms and the oxygen uptake of each component were calculated to study the diffusion behavior of oxygen atoms and the oxidation degree of each component under various cross-linking networks. Glass transition temperature (Tg) and interaction energy were determined to characterize the thermodynamic properties and interaction between asphalt phase and epoxy resin phase of epoxy asphalt before and after aging. The radial distribution function (RDF) was determined to simulate the distribution of asphaltene and epoxy resin crosslinked networks in different cross-linking networks. The results show that the formation of carbonyl groups, alcohol hydroxyl groups, and the fracture of methylene groups was observed during the photooxidative aging process of epoxy asphalt. The rise in the proportion of anhydride curing agents improved the stability of the chemical components in epoxy asphalt under photooxidation aging. High cross-linking density and methylene fracture weakened the diffusion ability of oxygen atoms in epoxy asphalt due to a reduction in free volume. In addition, photooxidation aging had a negative impact on the low-temperature performance and interaction between asphalt phase and epoxy resin phase of epoxy asphalt. However, a high content of acid anhydride alleviated the damage of photooxidation aging to low-temperature performance. Photooxidation aging developed the polar functional groups of epoxy asphalt, promoting the stacking of asphaltene under a high content of dicarboxylic acid curing agent, while breaking the stacking of asphaltene under a high content of acid anhydride curing agent.

In-Situ Young’s Modulus Characterization of Elastomeric Microfluidic Chips With Micropillars

This study presents a novel in-situ Young’s modulus measurement technique of polydimethylsiloxane (PDMS) microfluidic chips that are designed to measure fluid viscosities. In such chips, viscosity can be accurately determined once the Young’s modulus of PDMS is also known. Yet, the Young’s modulus values of elastomers are highly dependent on their chemical composition and curing temperature. The presented approach involves integrating a piezoelectric sheet underneath the chip, oscillating the chip through sweeping the drive frequency, and monitoring the blur and speckle contrast of the pillar via an external camera. A local maximum in the blur and speckle contrast is achieved at the fundamental resonance of the pillars, from which its Young’s modulus is predicted. The experimental results validate the relationship between the Young’s modulus of PDMS and base polymer:curing agent ratio, curing time, and temperature, demonstrating that it could be measured optically. Six different PDMS microfluidic chips prepared by curing elastomer at different temperatures and using different base polymer to curing agent ratios, 5:1, 10:1, and 20:1, were utilized. The Young’s modulus of the prepared sample microfluidic chips varied within the range of 0.72 to 3.64 MPa. The successful measurement of the Young’s modulus of PDMS using the proposed techniques demonstrates its potential in determining the mechanical properties of fluidic chips in-situ, with a low-cost and simple setup.

Mechanical and chemical properties of matrix composite: Curing agent ratio, degassing process, and filler effect perspectives

Epoxy resins are widely used as the matrix in fiber-reinforced polymer (FRP) composite because of their excellent properties. Epoxy properties were influenced by the mixing ratio and production process. This research focuses on studying the influence of the epoxy's mixing ratio on composite properties and the optimal duration for the degassing process. The addition of graphite filler was also studied in this paper. The sample was observed for its workability time, micrograph, spectrophotometer, and FTIR and was tested for tensile, bending, shore hardness, density, and moisture content. The result showed that 2:1 ratio achieved the highest tensile and flexural strength with 47.47 MPa and 191 MPa. Addition of 1 wt% of graphite powder resulted in highest bending strength of 199.51 MPa. The same ratio also achieved the highest shore hardness with a value of 78.2. The lower mixing ratio resulted in steeper and higher temperature progression in the curing process. The result also shows that degassing duration of 10 min is optimal to reduce the amount of trapped bubbles significantly.

Optimizing curing agent ratios for high-performance thermosetting phthalonitrile-based glass fibers

Abstract Phthalonitrile (PN) is a highly promising material in the field of high-performance thermosetting polymers due to its ability to maintain its properties even at extremely high temperatures. The goal of this study was to investigate the effects of varying curing agents on the thermal properties of cured PN resin. The curing agents were found to effectively cure the resin, as indicated by the increasing ratio of N and S contents and decreasing the C content as the proportion of curing agents increased, as observed by scanning electron microscopy and energy dispersive X-ray spectroscopy data analyses. Moreover, thermogravimetric analyses revealed that the sample with 20% curing agent showed the highest thermal decomposition rate among the 2, 5, 10, and 20% curing agent dosages. These properties can be further improved by incorporating glass fibers. Overall, these results demonstrate the successful use of curing agents to create an efficient and functional polymer with superior thermal properties that are suitable for use in harsh environments. The findings of this study are a significant step forward in advancing the use of PN as a high-performance thermosetting polymer.

Facile and cost-effective PDMS double-casting method based on curing temperature and ratio for solvent detecting applications

This study proposes a polydimethylsiloxane (PDMS) double-casting method based on curing ratio and temperature. The master mold is fabricated by first curing with high-temperature, high curing agent ratio of PDMS, followed by secondary curing with low-temperature, low-ratio PDMS to create a replica mold. The distribution of the Si–H stretch bonding and the CH3 symmetric and asymmetric stretching are altered when the curing temperature and curing ratio sequence is changed. The difference in the distribution of chemical bonds at the interface between the two molds results in double casting. Moreover, the roughness and water contact angle are measured to determine the changes in the surface properties of the master and replica molds after double casting. The double-casting method maintains the hydrophobicity of both the master and replica molds without altering the properties of PDMS. Furthermore, the one-dimensional pattern formed by the interlayer structure of the fused deposition modeling-type three-dimensional (3D) printing mold is successfully double cast. Finally, the chemical sensor for detecting the type of solvent was fabricated using the double-casting method and experimentally demonstrated. This study demonstrates a facile, simple, and cost-effective PDMS double-casting method for 3D-printed mold replicas.

Wearable Soft Microtube Sensors for Quantitative Home-Based Erectile Dysfunction Monitoring

Quantifiable erectile dysfunction (ED) diagnosis involves the monitoring of rigidity and tumescence of the penile shaft during nocturnal penile tumescence (NPT). In this work, we introduce Erectile Dysfunction SENsor (EDSEN), a home-based wearable device for quantitative penile health monitoring based on stretchable microtubular sensing technology. Two types of sensors, the T- and R-sensors, are developed to effectively measure penile tumescence and rigidity, respectively. Conical models mimicking penile shaft were fabricated with polydimethylsiloxane (PDMS) material, using different base to curing agent ratios to replicate the different hardness properties of a penile shaft. A theoretical buckling force chart for the different penile models is generated to determine sufficiency criteria for sexual intercourse. An average erect penile length and circumference requires at least a Young's modulus of 179 kPa for optimal buckling force required for satisfactory sexual intercourse. The conical penile models were evaluated using EDSEN. Our results verified that the circumference of a penile shaft can be accurately measured by T-sensor and rigidity using the R-sensor. EDSEN provides a private and quantitative method to detect ED within the comfortable confines of the user's home.

Experimental Study on Strength Characteristics of Zinc Contaminated Soil Solidified by Cement-Metakaolin-Limestone

In order to reveal the effect of curing agent ratio variable and curing age on zinc heavy metal contaminated soil solidified by cement-metakaolin-limestone (LC3) ternary mixture, artificial contaminated soil and curing agent were used to simulate the solidification of contaminated soil. Through a series of laboratory tests, the change rules of unconfined compressive strength and electrical conductivity after curing were analyzed. It is found that with the increase of curing age, the stronger the compressive strength is, the lower the moisture content is. The compressive strength of solidified soil decreases with the increase of moisture content, showing an obvious correlation. Thus it can be seen that the coupling substitution of high territory and limestone for cement can obtain lower moisture content and higher strength and excellent mechanical properties at a relatively early age. The pH value of solidified soil increased to 9.68-10.78. Considering many factors, the solidification effect of zinc heavy metal is the best when the ratio of cement, metakaolin and limestone is LC3-3.

Influence of curing agent ratio, asphalt content and crosslinking degree on the compatibility and component distribution of epoxy asphalt in compound curing agent system

ABSTRACT To study the effects of curing agent ratio, asphalt content, and crosslinking degree on the properties and distribution of epoxy asphalt with a compound system of dicarboxylic acid and acid anhydride, epoxy asphalt molecular models with two asphalt contents of 25% and 65% and three curing agent ratios of 10:1, 5:1 and 1:1 were constructed by Materials Studio. Various epoxy resin crosslinking degrees were further realised by Perl language crosslinking script. Glass transition temperatures were calculated to characterise low temperature flexibility. Energy systems and interaction energy were simulated to characterise the compatibility of epoxy asphalt. The radial distribution function (RDF) was calculated to observe the composition distribution of epoxy asphalt. The results show that the raise of the crosslinking degree and the proportion of anhydride curing agent increased the Tg of epoxy asphalt, impairing the low temperature performance. The increase in asphalt content was beneficial to the stability of the epoxy asphalt. Resin-based epoxy asphalt had stronger interaction between epoxy resin phase and asphalt phase, and the interaction energies both reached the maximum values at crosslinking degree of around 25%. Resin-based and asphalt-based epoxy asphalt had the most notable composition difference in the distribution of asphaltenes and acid anhydrides.

Fabrication of Wearable PDMS Device for Rapid Detection of Nucleic Acids via Recombinase Polymerase Amplification Operated by Human Body Heat.

Pathogen detection by nucleic acid amplification proved its significance during the current coronavirus disease 2019 (COVID-19) pandemic. The emergence of recombinase polymerase amplification (RPA) has enabled nucleic acid amplification in limited-resource conditions owing to the low operating temperatures around the human body. In this study, we fabricated a wearable RPA microdevice using poly(dimethylsiloxane) (PDMS), which can form soft—but tight—contact with human skin without external support during the body-heat-based reaction process. In particular, the curing agent ratio of PDMS was tuned to improve the flexibility and adhesion of the device for better contact with human skin, as well as to temporally bond the microdevice without requiring further surface modification steps. For PDMS characterization, water contact angle measurements and tests for flexibility, stretchability, bond strength, comfortability, and bendability were conducted to confirm the surface properties of the different mixing ratios of PDMS. By using human body heat, the wearable RPA microdevices were successfully applied to amplify 210 bp from Escherichia coli O157:H7 (E. coli O157:H7) and 203 bp from the DNA plasmid SARS-CoV-2 within 23 min. The limit of detection (LOD) was approximately 500 pg/reaction for genomic DNA template (E. coli O157:H7), and 600 fg/reaction for plasmid DNA template (SARS-CoV-2), based on gel electrophoresis. The wearable RPA microdevice could have a high impact on DNA amplification in instrument-free and resource-limited settings.

Batch Transfer Printing of Small-Size Silicon Nano-Films with Flat Stamp.

Silicon nano-film is essential for the rapidly developing fields of nanoscience and flexible electronics, due to its compatibility with the CMOS process. Viscoelastic PDMS material can adhere to Si, SiO2, and other materials via intermolecular force and play a key role in flexible electronic devices. Researchers have studied many methods of transfer printing silicon nano-films based on PDMS stamps with pyramid microstructures. However, only large-scale transfer printing processes of silicon nano-films with line widths above 20 have been reported, mainly because the distribution of pyramid microstructures proposes a request on the size of silicon nano-films. In this paper, The PDMS base to the curing agent ratio affects the adhesion to silicon and enables the transfer, without the need for secondary alignment photolithography, and a flat stamp has been used during the transfer printing, with no requirement for the attaching pressure and detaching speed. Transfer printing of 20 wide structures has been realized, while the success rate is 99.3%. The progress is promising in the development of miniature flexible sensors, especially flexible hydrophone.

Surface modifications to polydimethylsiloxane substrate for stabilizing prolonged bone marrow stromal cell culture

Polydimethylsiloxane (PDMS) has been extensively used as a supporting material for studies of cell mechanobiology, cell micropatterning and microscale-cell analysis in microfluidic chips due to its numerous advantages, such as low cytotoxicity, ease of modification, inexpensive costs and biocompatibility. However, the innate hydrophobicity of PDMS often poses a problem for stable cell adhesion, seriously limiting its applicability for prolonged cell culture. UV exposure and protein coating are suboptimal solutions, while chemical surface functionalization is often associated with laborious procedures and producing environmental toxics. Plasma treatment can render a hydrophilic substrate by altering the surface chemistry, but such effect is often short-lived due to its tendency to hydrophobic recovery. Variation of physical properties of the substratum are known to influence cell behaviour. Nevertheless, the combination of varying PDMS substratum properties via base:curing agent ratio and plasma treatment to stabilize the long-term culture of bone marrow derived stromal cells (BMSCs) still remain poorly understood. In this study, we developed a protocol to maintain the hydrophilicity of the plasma-treated PDMS over a range of substratum properties. This study demonstrated that varying the substratum properties of PDMS can enhance the stability of BMSC culture for at least three weeks, while plasma treatment with or without additional collagen coating further enhanced such effect. The changes in the physical properties of PDMS have rendered difference in BMSCs adhesion, proliferation and in-vitro plasticity, thereby offering a simple and effective strategy for PDMS surface modification to enable long term cell analysis in PDMS-based culture platform.

Low-temperature adhesion and the application on conductive treatment of curved-surface piezoelectric composite material

Good conductive treatment of curved-surface piezoelectric composites could prevent failure of curved transducers, which are the core devices of many wideband and high-frequency sonar systems. A series of ratio between epoxy resin and curing agent were tested to investigate conductive treatments of curved-surface piezoelectric composites. The curved-surface piezoelectric composite was first prepared. The sample whose epoxy resin to and curing agent ratio was 100:150 showed the largest welding spot strength in many areas, but its homogeneity was not as good as samples with epoxy resin to curing agent ratio of 100:100 or 100:200. With increases in curing agent, the volume resistivities decreased, and the homogeneity became better.

3D printed mold leachates in PDMS microfluidic devices

The introduction of poly(dimethylsiloxane) (PDMS) and soft lithography in the 90’s has revolutionized the field of microfluidics by almost eliminating the need for a clean-room environment for device fabrication. More recently, 3D printing has been introduced to fabricate molds for soft lithography, the only step for which a clean-room environment is still often necessary, to further support the rapid prototyping of PDMS microfluidic devices. However, toxicity of most of the commercial 3D printing resins has been established, and little is known regarding the potential for 3D printed molds to leak components into the PDMS that would, in turn, hamper cells and/or tissues cultured in the devices. In the present study, we investigated if 3D printed molds produced by stereolithography can leach components into PDMS, and compared 3D printed molds to their more conventional SU-8 counterparts. Different leachates were detected in aqueous solutions incubated in the resulting PDMS devices prepared from widely used PDMS pre-polymer:curing agent ratios (10:1, 15:1 and 20:1), and these leachates were identified as originating from resins and catalyst substances. Next, we explored the possibility to culture cells and tissues in these PDMS devices produced from 3D printed molds and after proper device washing and conditioning. Importantly, we demonstrated that the resulting PDMS devices supported physiological cultures of HeLa cells and ovarian tissues in vitro, with superior outcomes than static conventional cultures.

Tunability of liquid-infused silicone materials for biointerfaces.

The ability to control the properties of bio-inspired liquid-infused surfaces is of interest in a wide range of applications. Liquid layers created using oil-infused polydimethylsiloxane elastomers offer a potentially simple way of accomplishing this goal through the adjustment of parameters such as curing agent ratio and oil viscosity. In this work, the effect of tuning these compositional parameters on the properties of the infused polymer are investigated, including infusion dynamics, stiffness, longevity in the face of continuous liquid overlayer removal, and resistance to bacterial adhesion. It is found that that curing agent concentration appears to have the greatest impact on the functionality of the system, with a lower base-to-curing agent ratio resulting in both increased longevity and improved resistance to adhesion by Escherichia coli. A demonstration of how these findings may be implemented to introduce patterned wettability to the surface of the infused polymers is presented by controlling the spatial arrangement of bacteria. These results demonstrate a new degree of control over immobilized liquid layers and will facilitate their use in future applications.

Biological characterization of the modified poly(dimethylsiloxane) surfaces based on cell attachment and toxicity assays.

Poly(dimethylsiloxane) (PDMS) is a material applicable for tissue and biomedical engineering, especially based on microfluidic devices. PDMS is a material used in studies aimed at understanding cell behavior and analyzing the cell adhesion mechanism. In this work, biological characterization of the modified PDMS surfaces based on cell attachment and toxicity assays was performed. We studied Balb 3T3/c, HMEC-1, and HT-29 cell adhesion on poly(dimethylsiloxane) surfaces modified by different proteins, with and without pre-activation with plasma oxygen and UV irradiation. Additionally, we studied how changing of a base and a curing agent ratios influence cell proliferation. We observed that cell type has a high impact on cell adhesion, proliferation, as well as viability after drug exposure. It was tested that the carcinoma cells do not require a highly specific microenvironment for their proliferation. Cytotoxicity assays with celecoxib and oxaliplatin on the modified PDMS surfaces showed that normal cells, cultured on the modified PDMS, are more sensitive to drugs than cancer cells. Cell adhesion was also tested in the microfluidic systems made of the modified PDMS layers. Thanks to that, we studied how the surface area to volume ratio influences cell behavior. The results presented in this manuscript could be helpful for creation of proper culture conditions during in vitro tests as well as to understand cell response in different states of disease depending on drug exposure.