Epoxy Samples Research Articles

Study on the impact of grouting reinforcement on the mechanical behavior of non-penetrating fracture sandstone

The grouting reinforcement technology is an essential method to enhance the mechanical performance of fractured rock masses and the effectiveness of reinforcement varies with different grouting materials. To further understand the mechanical improvement capabilities of each grout and the reinforcement mechanisms at the grout-rock interface, this study prepared samples with different grouting materials (sulphoaluminate cement (SAC), ultra-fine cement (UFC), and epoxy resin (EPR)) and the uniaxial compression tests were conducted. Based on these tests, the macro and micro mechanical characteristics of different grouting samples were revealed using particle image velocimetry (PIV), acoustic emission (AE), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). The results indicate that grouting helps improve the mechanical performance and deformation resistance of fractured rock masses. It effectively limited lateral displacement of the samples, reduced stress concentration at fracture tips, enhanced shear effects during sample fracture, and altered the crack propagation process and failure modes. Compared to the fractured samples, the peak strength of SAC, UFC, and EPR samples increased by 17.8 %, 23.4 %, and 28.3 %, and the elastic modulus increased by 14.3 %, 7.9 %, and 24.8 %, respectively. Among these, the EPR samples exhibited a similarity in parameter indicators to intact samples of over 85 %, making EPR the optimal grouting material. The degree of grout-rock fusion is the primary factor influencing grouting reinforcement effectiveness. SAC is covering-type cement, UFC is embedded cement, EPR is a fusion material, and the fusion-type materials are more beneficial for improving the mechanical performance of fractured rocks.

Inverse problem-solving method applied to the acoustic characterisation of a thin film via the Debye series method (DSM)

ABSTRACT The study of the ultrasonic acoustic response of materials is of increasing interest for the characterisation of high-frequency applications. In this work, some elastic properties (acoustic velocity and acoustic attenuation) and some physical properties (thickness and density), together with the phase shift of the transducer, are estimated via one method. Scanning acoustic microscopy was performed via an innovative and different method using a high-frequency (50 MHz) planar wave transducer. In addition, the Debye series model (DSM) was used to model the acoustic response of the bilayer structure of the glass substrate and the resin‒epoxy sample. The inverse problem of estimating the acoustic parameters that results in a DSM reflected echo that matches the experimental signal is solved by proposing an innovative step-by-step curve fitting algorithm. The algorithm for solving the inverse problem is then optimised via relative mean square error (RMSE) curves, resulting in a robust method for assessing the uniqueness of the multiparameter solution.

Decreasing propagation rate of interfacial debonding between a single carbon fiber and epoxy matrix under cyclic loading

The interfacial debonding of a single carbon fiber transversely embedded in a dumbbell-shaped epoxy sample was generated under cyclic loading, and images were captured using synchrotron radiation X-ray computed tomography. A fatigue testing machine driven by a piezoelectric actuator placed along the beamline for in situ observation was developed for precise alignment. Interfacial debonding was initially observed under a static tensile load and was confirmed to be almost of the same length at both ends of the carbon fiber, implying negligible bending deformation due to inclination. Cyclic loads were then applied to the sample to capture the progressive debonding. The propagation rate of the interfacial debonding decreased as the number of cycles increased. Another sample with a single carbon fiber aligned parallel to the loading direction was prepared following a single-fiber fragmentation test. Interfacial debonding was clearly observed around the fiber breakage. Cyclic loads were also applied to this sample; however, no progression of the interfacial debonding was evident. Degradation of the interfacial strength between the carbon fiber and epoxy matrix was not confirmed under cyclic loading within the elastic deformation range.

Improved Corona Resistance of Epoxy Resin for Gas‐Insulated Equipment in Nitrogen Gas by Direct Fluorination

Direct fluorination has demonstrated efficacy in modulating the surface electrical properties of epoxy insulators and preventing surface charge accumulation. Comparative corona treatments were conducted on both surface fluorinated (modified) epoxy samples and untreated (virgin/original) samples using a modified electrode setup in a nitrogen (N2) atmosphere. The purpose was to evaluate the resistance of the modified epoxy surface layer against corona discharge. The results of ATR‐IR analysis and SEM surface and cross‐sectional imaging indicate that corona treatment did not alter the chemical composition of the fluorinated sample or the thickness of the fluorinated layer. Based on assessments of potential decay and water contact angle measurements, the surface conductivity of the modified sample was decreased by corona treatment. The wettability of fluorinated sample remained unchanged after corona treatment, and no soluble degradation products were produced. Conversely, the surface conductivity of the virgin sample exhibited an increase following corona treatment, accompanied by the formation of soluble degradation products. These results confirm that direct fluorination improves the epoxy insulator's discharge resistance in N2 and provides technical support for enhancing the electrical performance of epoxy insulators in gas insulated equipment. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Material compatibility of epoxies exposed to repeated low temperature vaporized hydrogen peroxide sterilization

ABSTRACT Through technological advancements, medical devices have evolved in their designs and have become more complex in both their design and materials of construction. Medical grade biocompatible epoxies are widely used in reusable medical devices. Choosing an epoxy that maintains its performance characteristics when subjected to repeated sterilization throughout the reusable medical device’s lifespan is a known challenge for medical device manufacturers. This study evaluated the material compatibility of seven cured 2-part and 1-part epoxies used in medical devices following exposure to 100 cycles in a low temperature vaporized hydrogen peroxide sterilizer. Six of the seven epoxies tested were found to be compatible with vaporized hydrogen peroxide sterilization based on qualitative, hardness and weight measurements conducted post exposure to 100 VHP cycles. The epoxies deemed to be compatible displayed no visual signs of physical defects, minimal reduction in hardness (≤2%) and total weight gain (≤2.9%). One of the epoxy samples did not maintain its texture and exhibited 17% loss in hardness post exposure to 100 VHP sterilization cycles and was found to be incompatible with the low temperature vaporized hydrogen peroxide process. This study verifies the need for material compatibility evaluations of epoxies prior to designing and developing a medical device while keeping in mind the application, lifecycle and intended use of medical devices.

Design and preparation of low-temperature curable, tough, repairable epoxy containing hindered urea-based dynamic reversible bonds

ABSTRACT Traditional epoxy resins are of technological significance for structural adhesives and composite materials, as well as many others. However, brittleness limits its further development, and achieving a combination of toughness and rigidity in epoxy networks remains a great challenge. In this work, we designed and synthesized low-temperature curable, tough and repairable epoxy networks via hindered urea bond (HUB) crosslinking strategies. Mechanical testing revealed that the material exhibited simultaneously improved toughness and stiffness, and specifically, tensile strength, elongation at break, and toughness were able to reach 78.2 MPa, 8.61%, and 4.63 MJ · m−3, respectively. More importantly, the dynamic exchange of HUB dispersed between polymer chains enables HUB crosslinked epoxy with thermal-triggered reparability and recyclability. In addition, thermal properties, chemical stability and water resistance of toughened epoxy samples were also characterized. This work provides a practical guidance for the exploration of high-performance epoxy with the potential to be extended to other polymers.

Hygrothermal effect and statistical analysis of the interfacial performance of nano and microscale polymer composites

ABSTRACT Hygrothermal exposure significantly impacts polymer composite (PMC) performance, affecting various industries. This study evaluated the short-term hygrothermal effects on PMCs by examining interfacial shear strength (IFSS), water uptake, glass transition temperature (Tg), and morphology. Data-driven techniques minimized experimental time while analyzing multiple factors. Specimens were immersed in water at 25°C and 70°C for 3, 7, and 14 days. The IFSS between carbon nanotube yarns and carbon fiber with epoxy (EPON™ 862) was measured before and after exposure. Statistical analysis indicated that fiber type significantly influenced IFSS, while time had a marginal effect and temperature had no impact. The IFSS decreased by 4.14% for CF/epoxy and 14.9% for CNT/epoxy. Water uptake analysis revealed weight gains of 0.465% and 1.566% for epoxy after 14 days at 25°C and 70°C, respectively. Morphological studies showed moisture penetration between 7 and 14 days. Thermomechanical analysis (TMA) indicated that pristine epoxy expanded by 0.318% of its original height. After 14 days, the Tg of epoxy decreased by 6.4% at 25°C and 9.7% at 70°C. Dynamic mechanical analysis (DMA) on dried epoxy samples showed similar Tg but varied tan delta curves due to plasticization. Short-term hygrothermal evaluation revealed degradation in interface quality and viscoelastic properties.

Emerging Mo-doped MgAl-LDH lamellar/carbon nanotubes as 3D sustainable nanohybrid for designing a durable smart anti-corrosion composite

This paper focused on the utilization of 3D hybrid nanocomposites composed of layered double hydroxides (L) containing sodium molybdate (SM), which are chemically bonded with functionalized multi-walled carbon nanotubes (FCN), as nanocarriers for smart corrosion prevention. The SM molecules were loaded into the L, and L/FCN nanocarriers by an anion exchange process, and then the 3 synthesized nanoparticles (L, SM-L, and SM-L/FCN) were characterized. Based on the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) tests' outcomes, the maximum corrosion prevention efficiency (about 90.88 %) belongs to the SM-L/FCN nano reservoir containing saline extract. Additionally, for the epoxy phase, the EIS results (on the intact and scratched specimens) revealed a significant diminish in the chloride and water penetration into the epoxy coating during 63 days of immersion for intact and 24 h for scratched states. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 17.42 kΩ.cm2 for the EP sample to 72.47 kΩ.cm2 for the SM-L/FCN/EP one in long immersion times, revealing the self-repairing behavior of the designed coating. The results of intact coating revealed that the Log (|Z|0.01 Hz) value reached 10.63 in long immersion time indicating a decreased occurrence of coating disbondment attributed to the electrolyte infiltration and corrosion of the underlying metal substratum. According to the pull-off and cathodic disbonding tests results, there was an enhancement in adhesion (51.5 % decrease in loss of adhesion strength, & a 52 % decline in diameter of cathodic disbondment), and a strong interaction between the interface of epoxy and substratum. According to the mechanical tests (tensile and DMTA) results the incorporation of L and FCN nanoparticles into the SM-L/FCN sample enhanced the nanocomposite's mechanical properties. The tensile test showed an increase in ultimate tensile strength (σUTS) and elongation at break (Ɛb) of 130.61 % and 107.59 %, respectively, compared to the pure epoxy (EP) sample. Additionally, the dynamic mechanical thermal analysis (DMTA) test indicated a 144 % increase in crosslinking density for the SM L/FCN sample compared to the neat epoxy.

The improvement mechanism of styrene grafted nano-Al2O3 on the hydrophobicity of epoxy resin composites: Based on molecular dynamics and experimental research

In the environment with high humidity, water will penetrate into the epoxy resin, resulting in the deterioration of the electrical properties and the decreasing resistance for the heat and corrosion. This study aims to utilize styrene grafted Al2O3 to improve the wettability of the epoxy resin surface and reduce the infiltration of water molecules into the epoxy resin interior. Firstly, the effects of doping PS/Al2O3 on the internal structure of epoxy resin and the diffusion process of water molecules within it are analyzed through the method of molecular dynamics (MD). Subsequently, epoxy resin samples with mass fractions of 1%, 3%, and 5% are prepared, followed by testing for hydrophobicity, water absorption, and the quality of surface condensation under different temperature differentials. The results indicate that the PS/Al2O3 and epoxy resin exhibit a strong interaction, reducing the proportion of free volume fraction of epoxy resin, which lowers the diffusion rate of water molecules. To be specific, the nanoparticles capture water molecules by forming hydrogen bonds with them, limiting the displacement of water molecules and reducing the water absorption of the epoxy resin (maximum reduction of 87%). Moreover, the addition of PS/Al2O3 decreases the adhesion energy of the material surface to water molecules, increasing the static contact angle from 103.58 ° to 125.42 °. Additionally, the total weight of condensation droplets on the material surface is reduced (maximum reduction of 26.02%). These findings serve as a reference for modifying epoxy resin materials in hygrothermal environments.

Verification of the Self-Healing Ability of PP-co-HUPy Copolymers in Epoxy Systems.

This work concerns the verification of the self-healing ability of PP-co-HUPy copolymers dispersed in epoxy systems. PP is the acronym for the Poly-PEGMA polymer, and HUPy refers to the HEMA-UPy copolymers based on ureidopyrimidinone (UPy) moieties. In particular, this work aims to verify whether this elastomer characterized by an intrinsic self-healing ability can activate supramolecular interactions among polymer chains of an epoxy resin, as in the elastomer alone. The elastomer includes a class of polyethylene glycol monomethyl ether methacrylate-based copolymers, with different percentages of urea-N-2-amino-4-hydroxy-6-methyl pyrimidine-N'-(hexamethylene-n-carboxyethyl methacrylate) (HEMA-UPy) co-monomers. The self-healing capability of these copolymers based on possible quadruple hydrogen bond interactions between polymer chains has been verified. The formulated epoxy samples did not show self-healing efficiency. This can be attributed to the formation of phase segregation that originates during the curing process of the samples, although the PP-co-HUPy copolymers are completely soluble in the liquid epoxy matrix EP. The morphological investigation highlighted the presence of crystals of PP-co-HUPy copolymers, which are in greater quantity in the sample containing the highest weight percentage (7.8 wt%) of HUPy units. Furthermore, the crystals act as promotors for increasing the curing degree (DC) of the epoxy systems containing HUPy units. DC goes from 91.6% for EP to 96.1% and 95.4% for the samples containing weight percentages of 2.5 and 7.8 wt% of HUPy units, respectively. Dynamic mechanical analysis (DMA) shows storage modulus values for epoxy systems containing PP-co-HUPy units lower than that of the unfilled resin EP. The values of maximum in Tan δ (Tg), representing the temperature at which the glass transition occurs, are 220 for the unfilled resin EP, 228 for the sample containing 2.5 wt% of HEMA-UPy units, and 211 for the sample containing 7.8 wt% of HEMA-UPy units.

Sustainable epoxy nanobiocomposites reinforced with lignin nanoparticles for enhanced UV resistance and mechanical properties

Lignin, a naturally occurring biopolymer derived from plant-based materials, possesses numerous multifunctional groups that can be leveraged in the synthesis of valuable nanoparticles (NPs) for the development of nano biocomposites. The in-situ polymerization method is employed as an initial step to incorporate lignin into the epoxy network system. This process involves the use of the curing agent MHHPA (hexahydro-4-methylphthalic anhydride), in combination with 1-MI (1-Methylimidazole) catalyzed lignin NPs, to integrate lignin into the epoxy polymeric matrix. The curing agent facilitates the creation of a crosslinked network within the epoxy resin, ensuring proper curing. The resulting nanocomposite films, formed by reinforcing the epoxy matrix with lignin NPs, exhibit exceptional UV-blocking capability, blocking approximately 33 % of UV radiation at 404 nm with a lignin content of 4.9 wt%. Furthermore, these nano biocomposites, derived from lignin NPs, demonstrate superior mechanical performance when compared to control epoxy composite samples. The inclusion of 4.9 wt% of degraded lignin epoxide in the nano biocomposite samples, as opposed to control epoxy samples, results in an 8 % increase in tensile strength. The successful integration of lignin NPs into the epoxy matrix not only enhances the UV-blocking capability but also improves the overall mechanical performance of the resulting nano biocomposites. This research opens up new avenues for the development of sustainable and high-performance materials by harnessing the unique properties of lignin.

Strain-based criteria for brittle failure prediction of solids containing blunt V-notches under pure mode I loading

This study introduces two novel failure criteria developed for the first time to predict the mode I brittle fracture behavior in components weakened by blunt V-notches. These criteria, named the Mean Strain (MST) and Point Strain (PST), rely on mean and point tangential strain components near the blunt V-notch border, respectively. The foundation of strain-based criteria has previously been used to predict brittle fracture in cracked samples under mixed-mode I/II and I/III loading conditions. Here, we investigate its applicability in predicting the fracture behavior of components weakened by blunt V-notches under pure mode I loading. To evaluate their accuracy, the proposed criteria undergo initial validation using available mode I blunt V-notch fracture experiment data across various materials like PMMA, graphite, and rock. Additionally, a series of fracture tests are conducted on brittle epoxy resin samples in rectangular plate forms weakened by blunt V-notches with varying notch opening angles and radii. The results exhibit good agreement between the outcomes using the developed strain-based criteria and the test results, particularly for specimens with larger notch tip radii. Notably, in certain materials, such as rocks, the proposed strain-based criteria offer more accurate predictions than the well-known stress-based (PS and MS) criteria.

Trisodium phosphate-loaded magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes self-assembled 2D-nanohybrid for designing a multifunctional smart epoxy nanocomposite

In this study, a hybrid nanomaterial based on layered double hydroxides (LDH) and multi-walled carbon nanotubes (MWCN) was fabricated using a co-precipitation method. Trisodium phosphate (TP) was loaded into the designed nanocarrier to enhance the corrosion resistance of mild steel in 3.5 wt% NaCl media. Fourier transform infrared (FT-IR) spectroscopy, Raman, and X-ray diffraction (XRD) analyses were carried out to investigate the magnesium‑aluminum layered double hydroxides/oxidized-multiwalled carbon nanotubes (Mg-AL-LDH/O-MWCN) structure and morphology before and after loading of trisodium phosphate. Furthermore, the nanocarrier inhibition capability was evaluated through electrochemical impedance spectroscopy (EIS), polarization, and field emission-scanning electron microscopy (FE-SEM) techniques. Electrochemical impedance spectroscopy (EIS) was also employed to estimate the anticorrosion properties of the epoxy coating loaded with TP-LDH/O-MWCN. The EIS evaluation of the intact coating revealed the impedance at the lowest frequency (|Z|0.01 Hz) of about 109 Ω.cm2 after 42 days of immersion for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample and the lowest value of breakpoint frequency was obtained for this sample (fb = 0.063 Hz). These findings prove the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes (TP-LDH/O-MWCN) particles' effectiveness in the epoxy coating water/ion barrier function enhancement. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 65.97 kΩ.cm2 for the pure epoxy (EP) sample to 94.87 kΩ.cm2 for the trisodium phosphate-layered double hydroxides/oxidized-multi-walled carbon nanotubes@epoxy (TP-LDH/O-MWCN@EP) sample, revealing the self-repairing behavior of the designed coating. In addition, the adhesion properties of the samples coated with LDH/O-MWCN@EP and TP-LDH/O-MWCN@EP were studied by pull-off and cathodic disbonding tests, leading to a 33% reduction in adhesion loss and a 52.23% reduction in the diameter of cathodic delamination. The tensile test conducted on the samples indicated an increase in the ultimate tensile strength (σUTS), elongation break (Ɛb), and toughness values by 188%, 223%, and 800%, respectively, in comparison with the pure epoxy (EP) sample.

Real-time tracking of curing process of an epoxy adhesive by X-ray photon correlation spectroscopy

Introduction: Cross-linkable polymers are in widespread use in a variety of industries because of their thermomechanical toughness, chemical resistance, and adhesive strength. But traditional methods to characterize these materials are insufficient for fully capturing the complex chemical and physical mechanisms of the crosslinking reaction. In this study, in situ X-ray photon correlation spectroscopy (XPCS) was used to investigate the crosslinking kinetics of a two-component epoxy resin adhesive.Materials and methods: With XPCS, we tracked the temporally resolved dynamics of silica filler particles, which served as probes of the internal dynamics of the thermoset network and allowed us to study the crosslinking process. The epoxy was cured isothermally at 40 °C and 80 °C to study the effects of curing temperature on the epoxy’s crosslinking reaction. XPCS results were compared to dielectric analysis (DEA) results, to demonstrate the similarities between a traditional technique and XPCS, and highlight the additional information gained with XPCS.Results and discussion: The epoxy resin was found to be highly sensitive to temperature. The epoxy samples exhibited different relaxation processes depending on isothermal cure temperature, indicating a complex relationship between applied temperature and the development of stress/relaxation conditions associated with formation of the thermoset network. Heating to the isothermal temperature setpoint at the start of curing promoted gelation, but the vitrification process was not completed during the isothermal curing stage. Instead, cooling the sample to room temperature facilitated the final vitrification process. This paper contextualizes this epoxy’s results within the broader field of thermoset study via XPCS, and advocates for XPCS as a fundamental technique for the study of complex polymers.

Research on Joint Sensing Technology for Vibration and Dielectric Spectrum of Power Equipment in the Context of New Power Systems

Abstract This paper has carried out the test results of SF6 gas decomposition products and the dielectric spectrum detection, proposed method for the identifying equipment defects based on decomposition products, and the partial discharge detection and diagnosis method for the equipment discharge defects. Combining the above two methods, the GIS discharge defects are comprehensively evaluated by decomposition products and partial discharge detection, achieving the type prediction of latent faults in operating switch-gear. In the aspect of vibration signal analysis, this paper conducts the wavelet analysis of the vibration signals and obtains frequency spectrum results under multi-layer wavelet decomposition. In the aspect of dielectric spectrum analysis, a model of three HN function superposition was used to fit the experimental data to verify the validity of the model, and the characteristic parameters such as the DC conductivity were extracted. It was found their dependence on temperature basically conformed to the Arrhenius formula. On this basis, the thermal aging test platform for the epoxy resin samples was established, and an accelerated thermal aging experiment was conducted at the temperature of 115 °C. The dielectric response test system was used to measure dielectric spectra of the samples with different aging times, compare the dielectric spectra at different aging times, and analyze the reasons for the differences.

Classical curing of epoxy modified lignin with polyamine for new Epoxy-Polyimine composite

Lignin, which is the most abundant aromatic polymer in nature was used as a green substitute for the toxic bisphenol A. Here we synthesized the epoxy agent from lignin by reacting lignin with epichlorohydrin. Further this product was reacted with the lignin-amine to give the new epoxy-polyimine composites. This study evaluated the curing of bio-based epoxy resins derived from lignin with aromatic and an aliphatic amine. The thermal stability of the cured lignin-based epoxy samples was evaluated. Epoxidation is an interesting way to develop new uses and applications of lignin. Lignin-based epoxy resins were obtained by the epoxidation reaction using the lignin recovered directly from pulping liquor. For the epoxidation reaction it was optimized the influence of the lignin:NaOH (w/w) ratio, temperature and time of the reaction on the properties of the prepared epoxidized lignin. The structures of lignin-based epoxy resins were evaluated by epoxy index test and FTIR spectroscopy. Optimal conditions were obtained for lignin-based epoxy resin produced at lignin/NaOH = 1/3 at 80 °C for 3 h. Thermogravimetry analysis (TGA) revealed that epoxidation enhances the thermal stability of lignin and may allow a wider temperature range for various applications.

Tensile properties and dynamic mechanical analysis of kenaf/epoxy composites

Kenaf fibre-reinforced polymer composites could offer low-cost, biodegradable, recyclable, and renewable materials. The hydrophilic kenaf fibres exhibit poor compatibility with the hydrophobic epoxy matrix as compared to their synthetic counterparts and ultimately, this may severely constrain their potential as a green composite material. This work aims to evaluate the tensile properties and dynamic mechanical analysis (DMA) of kenaf fibre composites reinforced with two epoxy systems as matrices, B and M resins. Neat epoxy samples and kenaf-reinforced composites with varying fibre loading, 15% and 45% were fabricated in the study. It was found that the tensile properties of kenaf composites are dependent on the epoxy resin systems and higher with reinforcement content. The tensile strength of M-15% and M-45% are 16.3% and 12.0% stronger than their counterparts. Determination of interfacial shear strength using a modified micromechanical model was employed showing that M-45 has a higher value than B-45%, 107.09 kPa and 90.28 kPa respectively. By DMA, in general, an increase in the storage modulus and peak height in the loss modulus was always higher with kenaf composites that were manufactured with the M resin system. The adhesion factor, A calculated from tan delta curves and cole-cole plot has shown the state of fibre/matrix adhesion level in each epoxy resin system. The SEM analysis indicates the presence of void spaces around fibres and matrix may attributed to the lower compatibility of the B resins system used in kenaf composites fabrication.

Characterization of Potting Epoxy Resins Performance Parameters Based on a Viscoelastic Constitutive Model.

To describe the evolution of residual stresses in epoxy resin during the curing process, a more detailed characterization of its viscoelastic properties is necessary. In this study, we have devised a simplified apparatus for assessing the viscoelastic properties of epoxy resin. This apparatus employs a confining cylinder to restrict the circumferential and radial deformations of the material. Following the application of load by the testing machine, the epoxy resin sample gradually reduces the gap between its surface and the inner wall of the confining cylinder, ultimately achieving full contact and establishing a continuous interface. By recording the circumferential stress-strain on the outer surface of the confining cylinder, we can deduce the variations in material bulk and shear moduli with time. This characterization spans eight temperature points surrounding the glass transition temperature, revealing the bulk and shear relaxation moduli of the epoxy resin. Throughout the experiments, the epoxy resin's viscoelastic response demonstrated a pronounced time-temperature dependency. Below the glass transition temperature, the stress relaxation response progressively accelerated with increasing temperature, while beyond the glass transition temperature, the stress relaxation time underwent a substantial reduction. By applying the time-temperature superposition principle, it is possible to construct the relaxation master curves for the bulk and shear moduli of the epoxy resin. By fitting the data, we can obtain expressions for the constitutive model describing the viscoelastic behavior of the epoxy resin. In order to validate the reliability of the test results, a uniaxial tensile relaxation test was conducted on the epoxy resin casting body. The results show good agreement between the obtained uniaxial relaxation modulus curves and those derived from the bulk and shear relaxation modulus equations, confirming the validity of both the device design and the testing methodology.

Study on Varied Bagasse Fiber and Epoxy Resin Compositions with Rice Bran Filler to Biocomposite Characteristics

<p>Natural fibers, with environmental, economic, and cost advantages, are highly sought-after for biocomposite materials. In the present study, the biocomposite samples of epoxy resin (as a matrix), bagasse fiber (as reinforcement), and rice bran (as a filler) were prepared. Tensile strength, strain, and Young's modulus will be the parameters concerning which the quality of the biocomposite can be tested. On the one hand, bagasse fiber is to be a strength enhancer in the resulting biocomposite. On the other hand, rice bran may increase the biocomposite's density. The process research comprises fiber yarn from milled bagasse, alkalized fiber with KMnO4, specimen printing process, and analysis. All the fibers were treated by soaking them in 3 grams of KMnO4 solution for 30 and 45 minutes. The fiber is drained in an oven at 50 °C for ±1.5 hours. The printed fiber onto a specimen mold was printed with a mixture of epoxy resin and rice bran (1:1 w/w) and left for one day. Variation in the fiber mass was at 3, 4, and 5 grams. The sizes of the specimens were similar to the size of the mold according to ASTM D-638 type IV. Then, the fibers were removed from the mold and tested for tensile strength, strain, and Young's modulus. The results show that the greater the fiber mass, the greater the tensile strength value. These findings indicate that the tensile strength was optimized after soaking for 45 minutes with 5-gram fiber weight, which resulted in the tensile strength of 26.32±0.25 MPa, strain of 9.65±0.14%, Young's Modulus of 3.29±0.05 MPa, and water absorption of 41.99%.</p>

Effects of reservoir fluids on sand packs consolidated by furan and epoxy resins: Static and dynamic states

One of the most effective methods for sand control is the chemical consolidation of sandstone structures. In this paper, the impacts of crude oil and brine in the static state and the impact of the flow rates of the fluids in the dynamic state have been assessed at the reservoir conditions. The analyses in this research were Young's modulus, compressive strength, porosity, and permeability which were done on core samples after and before fluid contact. Samples made with two different resins showed good resistance to crude oil in both states. No considerable change was seen in the analyses even at high crude oil injection rates in the dynamic state. Conversely, brine caused a noticeable change in the analyses in both states. In the presence of brine at the static state, Young's modulus and compressive strength respectively decreased by 37.5% and 34.5% for epoxy cores, whereas these parameters respectively reduced by 30% and 41% for furan cores. In brine presence at the dynamic state, compressive strength reduction was 10.28 MPa for furan and 6.28 MPa for epoxy samples and their compressive strength reached 16.75 MPa and 26.54 MPa respectively which are higher than the critical point to be known as weak sandstone core. Moreover, Young's modulus decrease values for furan and epoxy samples were respectively 0.37 GPa and 0.44 GPa. Therefore, brine had a more destructive effect on the mechanical characteristics of samples in the static state than the dynamic one for two resins. In addition, brine injection increased permeability by about 13.6% for furan and 34.8% for epoxy. Also, porosity raised by about 21.8% for furan, and 19% for epoxy by brine injection. The results showed that the chemical sand consolidation weakens in the face of brine production along with crude oil which can lead to increasing cost of oil production and treating wellbore again.