Resin Ratio Research Articles

Optimizing Thermosetting Epoxy Asphalt with Styrene–Butadiene Rubber and Styrene–Butadiene–Styrene Modifiers for Enhanced Durability in Bridge Expansion Joints

The high- and low-temperature performance of asphalt-based seamless expansion joints seriously affects road performance. The purpose of this paper is to explore the application of thermosetting epoxy asphalt-based materials in bridge expansion joints. The composite modification of asphalt was performed using Styrene–Butadiene rubber (SBR) and Styrene–Butadiene–Styrene (SBS) copolymer. The study then investigates the impact of five different dosages of SBR/SBS-modified asphalt on the performance of epoxy asphalt. The results of the cone penetration test, tensile test, and stress relaxation test of SBR/SBS-modified epoxy asphalt (SSEA) and BJ200 (a commercial Seamless expansion joint material) were comparatively analyzed. The Marshall test, rutting test, three-point bending test, and freeze–thaw split test were used to evaluate the road performance of SSEA mixtures. The test results show that with the increase in asphalt content, the shear resistance and tensile strength of SSEA decrease, and the low-temperature relaxation ability and elongation at break increase. The content of SBR/SBS-modified asphalt has a positive effect on the low-temperature performance of SSEA mixtures, and the residual stability in water and freeze–thaw splitting strength ratio (TSR) are higher than that of BJ200. Based on the requirement of balancing high and low-temperature performance, SSEA-3 has the best overall performance, and the dosage of SBR and SBS modifier is 12% and 2.5%, respectively. The ratio of epoxy resin, SBR/SBS-modified asphalt, and the curing agent is 1:4:1.6, and its use is recommended in areas with slight temperature differences.

SHEAR STRENGTH PARAMETERS AND DEFORMABILITY PROPERTIES OF SILICATE-BASED RESIN ADDED SAND-TYPE SOIL SPECIMENS

In this study, the shear strength, uniaxial compressive strength (UCS) values and deformability properties of silicate-based polymer resin added silty sand type soil specimens were examined through a series of experimental studies. Although the UCS and shear strength values increased, minor decreases in the internal friction angle values were measured as the resin ratio increased. It was determined that the main reason of improvement in the strength values due to the increase in resin content is the increase in cohesion values. It was found that the UCS values calculated according to the cohesion and internal friction angle parameters of the Mohr&Coulomb failure criterion (UCSc) were 2.6-3.0 times lower than the values obtained from the direct UCS experiment. According to this finding, it was concluded that the Mohr&Coulomb failure criterion is not properly usable to represent the mechanical behaviors of resin added sands. As another outcome, the ratio between UCS/UCSc slightly decreased with an increase in the resin amount. In other words, it has been determined that the Mohr&Coulomb failure criterion gives a bit more inaccurate results for the specimens with low binder contents. With the increase in the resin content ratio, significant increases were obtained in both elastic modulus and ductility properties of the samples. It has been evaluated that the silicate-based polymer resin binder is advantageous to provide significant increases in the toughness and energy absorption capacity of soils.

Mechanical properties of chicken feather modified soy protein‐based resins and jute fabric‐reinforced green composites

AbstractAgricultural wastes and byproducts offer a vast avenue for replacing commonplace, but environmentally unfavorable, petroleum‐based plastics. Chicken feather fiber (CFF), soy protein isolate (SPI), and jute fabric (JF) are three agricultural materials that can be utilized for creating ‘green’, that is, from nature, resins and composites. This study details the preparation of CFF‐loaded SPI (CFF/SPI) resins and JF/(CFF/SPI) hybrid green composites, both with and without the frequently used toxic crosslinking agent glutaraldehyde (GA), and their respective mechanical properties. Results showed that as CFF loading increased from 0% to 30%, the tensile fracture stress and strain of CFF/SPI resins decreased from 25.2 to 14.3 MPa and from 4.0 to 1.4% respectively, suggesting that CFF acted mostly as filler. JF/(CFF/SPI) composites had higher tensile properties compared to CFF/SPI resins, with fracture stresses and strains ranging from 26.6 to 22.0 MPa and 4.3% to 5.8%, respectively, as CFF loading increased from 0% to 30%. Apart from increasing the flexural modulus, CFF loading did not significantly affect the flexural properties of JF/(CFF/SPI) composites. With any addition of CFF, CFF/SPI resins and JF/(CFF/SPI) composites showed higher mechanical properties than their GA‐crosslinked counterparts, demonstrating that the toxic crosslinker was unnecessary when using the procedure in this work.Highlights Fully green composites produced with viability for furniture applications. Mechanical performance of GA‐free SPI resin negated need of toxic crosslinker. CFF reduced warpage when incorporated into SPI resin, and JF/SPI composite. JF/(CFF/SPI) composites found to be superior mechanically to all CFF/SPI resins. JF/(CFF/SPI) composite mechanically optimized at 10/90 CFF/SPI resin ratio.

Enhancing the performance and revealing the thermal behavior of the water-based coating derived from waterborne alkyd resins and totally methyl etherified amino resins

In this study, the curing parameters of the water-based coating were carefully optimized using waterborne alkyd resins as the matrix resin and totally methyl etherified amino resins as the crosslinking agent. Through an orthogonal experimental design and a controlled experiment, the optimal conditions, which were a 7:1 ratio of alkyd resins to amino resins and curing at 403.15 K for 30 min, were determined. Droplet size distribution and zeta potential measurements confirmed that the composite resin emulsion prepared with the optimal ratio was more uniformly and stably dispersed in water, which helped to optimize the coating and make it have excellent physical properties, mechanical stability and chemical durability. Thermal stability was also thoroughly evaluated by TGA analysis, paying particular attention to the third degradation stage of the optimized composite resin coating (573.15–733.15 K), pyrolysis kinetic analysis provided deeper insights into its thermal behavior. Activation energies calculated through both the KSA and Starink methods exhibited consistent values of 195.47 kJ/mol and 196.06 kJ/mol, respectively. Furthermore, a reaction mechanism function of G(α) = [−ln(1-α)]3 via C-R method implying a sigmoidal rate equation or stochastic nucleation. The activation energy calculated by this method is 211.10 kJ/mol and the pre-exponential factor is 2.22 × 1016 min−1. Notably, the thermodynamic parameters obtained from all three methods show remarkable agreement.

Separation of hafnium from zircon leach solution using anion-exchange resin and production of high-purity zirconia for nuclear applications

The ion exchange process using an anion exchange resin (Bio-Rex 5) was employed with batch and column techniques to isolate nuclear-grade zirconium/hafnium from a leach solution of zircon ore. Batch studies were conducted to optimize the conditions for sorption and desorption of Zr(IV) and Hf(IV). The highest separation factor of 10.3 was achieved under equilibrium conditions of 11.0 mol/L HCl, contact time of 30.0 min, solution volume-to-mass of resin ratio of 0.10, and 15 °C. The sorption process for both metals obeyed a pseudo-second-order model and the experimental sorption data was well-described by both Langmuir and Freundlich models. The maximum sorption capacities were determined to be 46.2 mg/g for Zr(IV) and 37.8 mg/g for Hf(IV). The Zr(IV) and Hf(IV) ions were effectively desorbed by 0.1 mol/L nitric and 2.0 mol/L hydrochloric acid solutions, respectively, with total yields of 89.7 % Zr(IV) and 85.8 % Hf(IV) via multistage desorption processes. In both batch and column techniques, the resin exhibited sorption selectivity for Zr and Hf over interfering elements in the hydrochloric acid leach solution of zircon sand. The loaded resin from real leach solution was subjected to desorption, zirconium sulfate precipitation, and calcination at 650 °C, resulting in a pure zirconia powder suitable for nuclear applications. This technique presents a promising effective method for the selective separation and recovery of high-purity zirconium and hafnium from their natural sources.

Mechanical analysis of polyester resin using digital image correlation and finite element method

The primary objective of this study is to perform a comprehensive mechanical analysis of unsaturated polyester (UP) resin under unidirectional tensile loading. The Digital Image Correlation (DIC) technique was employed to accurately determine the mechanical properties of the material, with full-field strain measurements used to extract both transverse and longitudinal strains through virtual extensometers. This approach facilitated the precise calculation of the Poisson’s ratio of the UP resin. The results obtained via DIC demonstrated strong correlation with the experimental data obtained through the machine’s control software, particularly in capturing vertical displacement and longitudinal strain with high precision. The Poisson’s ratio was found to be 0.46. To further validate the DIC findings, Finite Element Analysis (FEA) was conducted. The FEA results aligned closely with the experimental data, confirming the reliability and accuracy of the DIC method in this context. The values of Young’s modulus determined from experimental tests and FEA data were 3620.02 MPa and 3598 MPa, respectively, with a percentage error of only 0.61%.

Benefits of Environmentally Friendly Plaster on Mechanical Properties When Combined with Polyester Resin and Hardener Are Examined under Compression and Tension.

Recently, plaster has gained increasing attention as a mechanical and environmentally friendly option and is an effective alternative to traditional cement products. Additionally, polyester has an effective impact on the mechanical properties of materials, in addition to being one of the most environmentally friendly materials. However, studies are still ongoing to reach the best ratios of polyester resin, polyester hardener, and gypsum plaster that can improve mechanical properties. This research aims to investigate the impact of these components at various ratios (30%, 45%, and 60%) of gypsum plaster weight on the mechanical properties of plaster material. This study is carried out by conducting compression and tensile tests for three ratios, which are considered among the most important mechanical tests according to their applications. In addition, the environmental emissions resulting from the three different ratios of plaster are evaluated to determine their environmental impact. This study found that the largest ratio (30%) was the most effective from an economic and mechanical point of view, while achieving lower carbon emissions compared to the other ratios, which enhances the trend towards achieving the environmental goals of the Kingdom of Saudi Arabia's Vision 2030 to reach zero emissions. This study is highly significant both in terms of scientific research and practical application across a range of industries, since it integrates the enhancement of material performance with the achievement of environmental sustainability requirements.

CO2-Induced In-Situ Targeted Precipitation of Asphaltene in Heavy Oil Reservoirs: Balancing Formation Gas Channeling Regulation and Wellbore Asphaltene Blockage Prevention

Summary To investigate the mechanisms of the asphaltene precipitation in oil caused by CO2, the sandstone core oil displacement experiments and asphaltene structure observation experiments are designed in this work. The oil displacement experiments create CO2 flooding conditions under different pressures in heavy oil reservoirs and analyze the produced oil components and precipitated asphaltene proportions. Meanwhile, nuclear magnetic resonance (NMR) analysis is conducted on the sandstone cores to discuss the precipitation characteristics of asphaltene in the reservoir pores. The observation experiments analyze the microstructure of precipitated asphaltene after interactions between oil and CO2. The results show that the increasing pressure promotes the precipitation of asphaltene from oil by enhancing the dissolution and component extraction of CO2 in oil, which reduces oil viscosity and promotes reservoir development efficiency. This process also leads to an increase in CO2 sequestration in the reservoir. However, the precipitated asphaltene reduces reservoir permeability, hindering the optimization of the oil recovery rate. During the process of increasing pressure, the rate of increase in oil recovery decreases. In reservoirs containing oil with high asphaltene proportion, the oil recovery rate even decreases under high pressure. Additionally, in-situ targeted precipitation and retention of asphaltenes in large pores can reduce the distribution differences of pores with different sizes in the reservoir, weakening the above negative effects and enhancing oil recovery by regulating gas channeling. Moreover, the ratio of resin in oil affects the asphaltene precipitation form, and CO2 can promote the association of asphaltenes by weakening the steric stabilization effect of resin on asphaltene in oil, which makes the microstructure of precipitated asphaltenes dense and regular and promotes asphaltene precipitation and oil recovery increasing. This work aims to verify the advantages of CO2-induced asphaltene precipitation in improving the efficient and environmentally friendly development of heavy oil reservoirs, while exploring the significance of CO2 flooding in promoting carbon sequestration.

The impact of altering the molar ratio on formaldehyde content and the physical and mechanical properties of MDF panels

This study aimed to evaluate the influence of the molar ratio of urea-formaldehyde resin (UF) on formaldehyde content and the physical and mechanical properties of MDF panels. The goal was to determine the optimal composition, i.e. the one that exhibits the lowest formaldehyde content without compromising the properties. To that end, there were five treatments. They were characterized by five F:U molar ratios (0.9:1; 1.0:1; 1.1:1; 1.2:1; and 1.3:1). The panels had a nominal density of 750 kg.m−3, dimensions of 40 × 40 × 1.5 cm, 12% resin, 1% paraffin. They were produced with a pressing cycle with a temperature of 170 °C and pressure of 3.6 MPa per 10 min. The physical-mechanical properties of the panels and the formaldehyde content were determined and evaluated following the NBR 15316-2 (2019) standard. Results showed that the formaldehyde content was lower for panels produced with resin molar ratios of 0.9:1, 1.0:1, and 1.1:1, classified as E1. Panels with a resin molar ratio of 1.2:1 were classified as E2. The molar ratio of 1.3:1 exceeded the limits of the standard. Panels with resin molar ratios of 1.1:1, 1.2:1, and 1.3:1 met the standard requirements for all physical-mechanical properties of non-structural MDF for use in dry conditions. These results indicate that the most suitable UF resin molar ratio for producing MDF panels is 1.1:1. This radio provides low formaldehyde content and technological properties compatible with the reference standard.

Ketone modification of alkyd synthesized from waste PET as a sustainable option: A comparative study of coating and thermal properties of alkyd–melamine–ketone resin systems

AbstractThis study aims to prepare alkyd–melamine–ketone combinations from short‐oil alkyd resins synthesized using coconut oil fatty acid and waste poly(ethylene terephthalate) (PET) intermediate (bis(2‐hydroxyethyl) terephthalate, BHET) for coating applications with a green technology approach. For this aim, waste PET flakes obtained from post‐consumer water bottles were depolymerized by the glycolysis reaction. Purified depolymerization intermediate (BHET) was incorporated into the formulation of the four‐component alkyd resin, completely instead of the diol. For comparison, reference alkyds without waste PET were also synthesized. Then, ketone modifications of alkyd resins were carried out using cyclohexanone formaldehyde (CHF) resin by blending method. For this, firstly, melamine formaldehyde (MF) resin was added to the alkyd resin at a ratio of 40% by weight to obtain alkyd–melamine formaldehyde (Alkyd–MF) resin. Then, ketone‐modified blends were prepared at ratios of Alkyd–MF/CHF of 80/20, 70/30, 60/40, and 50/50 by weight. The effect of using ketone (CHF) resin at different ratios and the presence of BHET on the coating properties and thermal behaviors of alkyd–ketone blend films were investigated. At the end of the study, high‐gloss (151–154 GU) and medium‐hard (71–120 König second) films exhibiting excellent adhesion (100%) were obtained from alkyd–ketone blends. In both the reference and PET‐based blend series, adding CHF resin to the alkyd–amino (Alkyd–MF) resin improved all physical coating properties. Moreover, with increasing CHF resin ratios, hardness, gloss, and abrasion properties increased in both series. Although acceptable and usable results have been obtained in all ratios of CHF resin (20%, 30%, 40%, and 50%), the optimum CHF resin ratio for each physical coating properties has changed depending on the desired properties and expectations. These blend films resisted corrosive chemicals such as concentrated alkali, acid, and salt solutions for 72 h without damage, and at the end of the 18 h not affected by water. Acetone, toluene, methanol, and ethyl acetate did not affect these films in any way. All films performed excellently in repeated environmental resistance testing over 10 cycles, simulating changing climate conditions. In the chemical coating tests, superior results were obtained with all CHF resin ratios. The thermal resistance of Alkyd–MF/CHF blend films was found to be quite high. The incorporation of CHF resin into the alkyd–amino (Alkyd–MF) resin improved thermal resistance, and as the amount of CHF resin increased the thermal stability increased in both blend series. Moreover, the thermal resistance of PET‐based blend films was higher than their counterparts in reference blends due to the use of long‐chain BHET having an aromatic unit.Highlights Alkyd–MF/CHF blends using alkyds with and without PET were prepared. Good physical/excellent chemical coating properties/high thermal resistance. Incorporation of CHF into Alkyd–MF improved coating/thermal properties. CHF significantly improved the individual alkali resistances of the alkyd. As CHF increased, physical coating properties/thermal resistance increased. The thermal stabilities of the PET‐based blend were even higher.

Research on the diffusion plugging mechanism of flowing water grouting slurry in karst pipelines

Among the many adverse geological disasters, the surge water disaster in karst areas causes the greatest loss to underground engineering construction, so it is necessary to carry out relevant research on the management of surge water disaster in karst pipelines. This study presents the creation of an oily epoxy resin magnetic convergence grouting material (OEMS) specifically developed to prevent water infiltration in pipelines. A self-designed visual karst pipeline grouting simulation system was used to conduct an experimental study on the diffusion and plugging behavior of magnetic slurry grouting. A model was constructed to simulate the migration of a magnetic slurry in water inrush circumstances. The model is based on the theory of slurry diffusion and the concept of magnetic adsorption. The results suggest that:(i) The best performance in grouting sealing is achieved when the ratio of new OEMS epoxy resin A liquid to B liquid is 2:1, and the blending ratio of flyash and Fe3O4 powder falls between 25 and 55%. (ii) The primary and secondary correlations among the parameters that affect the rate of change in flow rate, plugging pressure, and slurry retention rate are as follows: Hydrodynamic velocity has the greatest correlation, followed by plugging length, Fe3O4 power ratio, and flyash mixture ratio. (iii) The validity of the model is verified by comparing empirical observations with calculated theoretical values.

Wear Performance Evaluation of Polymer Overlays on Engine Bearings.

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

The impact of ecological aging on the mechanical performance of jute-banana fibre phenol-formaldehyde hybrid composites

Natural fiber composites provide an environmentally favorable and sustainable alternative to traditional materials, greatly reducing environmental impact. Aging tests are required to evaluate the long-term mechanical performance and durability of these composites under varied situations, ensuring their dependability and safety over time. This study investigates the effects of ecological aging on jute-banana fiber reinforced phenol-formaldehyde (JBP-F) composites. The experiment involved fabricating JBP-F composites using jute and banana fibers with varying weight ratios (60:40, 50:50, 40:60, 30:70) and subjecting them to various aging tests like long-time water resistance, accelerated water resistance, thermal aging, hydrothermal aging, soil burial test, and accelerated weathering test. The result showed that the composite with a 50:50 jute-banana fiber to resin ratio (JBP-F50) outperformed the other compositions examined in terms of aging resistance. This balanced ratio likely optimized fiber-matrix interaction, leading to superior strength and water resistance. Higher fiber content composites (like JBP-F60) absorbed more water due to weaker bonding, while lower fiber content (JBP-F30) suffered more in high temperatures. All composites experienced strength loss during thermal and hydrothermal aging due to heat and moisture cycles. JBP-F50 again showed the least degradation, possibly due to the resin’s ability to recover. In soil burial tests, biodegradation impacted strength, with higher fiber content composites (JBP-F60) degrading more. Finally, weathering tests revealed some surface deterioration due to UV radiation. However, the resin offered protection, with JBP-F30 (higher resin content) experiencing the most weight loss.JBP-F50, with its balanced fiber-resin ratio, demonstrated the best resistance to various environmental stresses, making it a promising option for sustainable composite applications.

Research on the wear resistance and impact resistance of modified rubberized concrete

Rubber can improve the ductility and durability of concrete and reduce compressive strength. Tests were conducted to investigate the mechanical properties, wear resistance, and impact resistance of modified rubberized concrete (MRC) by mixing basalt fibers (BF), curing agent, and epoxy resin mixture. The results showed that the epoxy polymer improved the flowability of the rubberized concrete. The BF changed the failure mode of the rubberized concrete and enhanced the mechanical properties. When the curing agent-epoxy resin ratio was 4:8, the wear rate of BF6E8C4 after 120 times was 4.59 kg/m2, which was 70.02% and 3.77% less than that of BF2E8C4 and BF4E8C4. The impact strength of BF6E8C4 was increased by 256% and 409% compared with the BF2E8C4 and BF4E8C4, respectively. By analyzing the mechanism of the synergistic modification of BF and epoxy polymer, it was found that the synergistic work of BF and epoxy polymer could make the internal structure of concrete denser. At last, the wear damage and impact damage models of MRC were established, and the coefficient of determination exceeded 0.92.

Synthesis of a water‐soluble high hydroxymethyl content phenolic resin crosslinker and the associated polyacrylamide weak gel property investigation

AbstractAs an in‐depth profile control agent, water‐soluble phenolic resin crosslinking polyacrylamide weak gel has been widely used in the middle and high water cut stage of water flooding reservoir. In this study, the phenolic resin was synthesized by two‐step alkali catalysis. Factors influencing the synthesis of phenolic resin, including the molar ratio of phenol and formaldehyde, catalyst types, reaction time, were investigated with hydroxylmethyl and aldehyde content as the criterion. When the molar ratio of phenolic resin was 1:2 and NaOH was catalyst, at 80°C for 4 h, the phenolic resin had the highest hydroxymethyl content (49.37%) and the lowest free aldehyde content (2.95%). Weak gel was formed by the reaction of LT002‐polyacrylamide with phenolic resin. Taking the gelation time and strength as criteria, the factors influencing the crosslinking property, including hydroxymethyl content, crosslinker addition, and polyacrylamide concentration were investigated respectively. Under optimal formulation, the property investigation shows that the hydroxymethyl group in the phenolic resin can be crosslinked with the amide group in polyacrylamide, the gelation time is long (50–60 h), and the gelation strength is larger than 5 × 104 mPa s, which is conductive to the plugging of deep oil layers. When the permeability was 5061 × 10−3 μm2, the plugging rate was 72.73%.

Performance of optimized composition of epoxy resin adhesive used in High Friction Surface Treatment

The High Friction Surface Treatment (HFST) paving technique is widely employed in engineering practices globally, serving to enhance the long-term anti-skid performance of pavements. However, there still exist significant gaps in research regarding the modified and optimized composition and corresponding content of the polymer binding materials used in HFST, as well as the performance of the pavements laid with modified and optimized blended aggregates during service. To address these issues, this research first modified and optimized the composition ratio of traditional epoxy resin materials. Subsequently, a toughened, high-flow epoxy bonding system suitable for the maintenance of concrete pavements was prepared. Additionally, the study explored the bonding performance of this system with both the cement base surface and aggregates. The results established that the optimal ratio range for the modified epoxy adhesive system is E51 epoxy resin to curing agent to toughening agent to diluent in the proportions of 100: 30–35: 20–30: 5. The experimental group used a high-flow epoxy resin adhesive ratio of E51 epoxy resin: curing agent: toughener: diluent = 100:30:20:5. For control group 1, the ratio of epoxy resin adhesive was E51 epoxy resin: curing agent = 100:30, and for control group 2, the ratio was E44 epoxy resin: curing agent = 1:1. Compared with control groups 1 and 2, the modified epoxy system with the cement base demonstrated a 149 % increase in average pull-off strength and an 18 % increase in average shear strength. Similarly, in comparison with control groups 1 and 2, the modified epoxy system with aggregates exhibited a 174 % increase in average pull-off strength and a 541 % increase in average shear strength. Based on the pull-off and shear test results, it was ultimately determined that the dosage of modified epoxy binder for HFST mixtures should be controlled at 1.0–1.2 kg/m2, and the dosage of aggregate should be controlled at 3.3–4.3 kg/m2. These findings provide valuable insights into optimizing HFST pavement compositions for improved performance and longevity.

Impact of different matrix systems on mechanical, thermal, and electrical properties of carbon fiber reinforced epoxy resin matrix composites

AbstractCarbon fiber reinforced epoxy resin matrix composite is one of the most important composite materials in the world. Many researchers have conducted a lot of research on epoxy resin matrix systems in recent years, mainly to improve the problem with the short curing time of the matrix system and epoxy resin's high viscosity. The final aim is to enhance various aspects of composites' performance and optimize the production process. A new type of water dispersed epoxy resin matrix system is investigated in this paper and the target is to optimize the mechanical, thermal, and electrical performances of the composites with the water dispersed epoxy resin matrix by varying different doping particles and different resin/catalyst ratios. Through a series of experiments, it is evident that varying the ratio of resin to catalyst in the matrix system will not significantly improve the mechanical as well as thermal properties of the composites. However, increasing the amount of catalyst in the matrix system can greatly improve the electrical properties of its composite samples. In addition to this, the addition of doping particles to the matrix systems has the effect of slightly enhancing the tensile modulus, thermal conductivity, and electrical conductivity of their composites.Highlights A new water‐dispersed epoxy resin matrix system improves processing technology. Increasing amount of catalyst in the matrix system improves electrical resistivity. Adding particles to matrix systems has a slight effect on different properties.

Multi-frequency composite wearable antenna for wireless communications

This paper proposes a multi-band composite wearable antenna for wireless communication, which uses a monopole structure as the radiating body and achieves multi-band characteristics through slit-loading and multi-branching methods. A polymer composite substrate with high dielectric constant and low dielectric loss was prepared using in situ polymerization, and the optimal dielectric constant and loss angle tangent were obtained by controlling the coating ratio of melamine formaldehyde resin to carbon nanotubes (MWCNTs) and the filler doping rate to achieve miniaturization of the antenna. Comparative experimental results show that the obtained composites have high flexibility and good dielectric properties. The antenna operates in the frequency bands of 2.21–2.52 GHz, 3.07–3.87 GHz, and 4.36–6.03 GHz, which cover the frequency bands of WLAN and WiMAX and 5G applications. The antenna was fabricated and tested, and its performance roughly matched the simulation results. Meanwhile, the antenna has passed the SAR safety test and maintained a stable performance under different curvatures, so it has potential applications in the wireless communication system.

Effects of Chemical Composition and Cross-Linking Degree on the Thermo-Mechanical Properties of Bio-Based Thermosetting Resins: A Molecular Dynamics Simulation Study.

Bio-based epoxy resins have received significant attention in terms of concerns regarding carbon emission. Epoxidized soybean oil (ESO) derived from sustainable feedstock has been widely used to blend with traditional diglycidyl ether of bisphenol-A (DGEBA) to replace some of the petroleum-based components. In this work, molecular dynamics (MD) simulations were applied to track the network formation and predict the performance of methyl hexahydrophthalic anhydride (MHHPA)-cured ESO/DGEBA blend systems. The effects of ESO content and cross-linking degree on the mass density, volumetric shrinkage, glass transition temperature (Tg), coefficient of thermal expansion (CTE), Young's modulus, yield strength, and Poisson's ratio of the epoxy resin were systematically investigated. The results show that systems with high ESO content achieve gelation at low cross-linking degree. The Tg value, Young's modulus, and yield strength increase with the increase in cross-linking degree, but the CTE at the glassy state and Poisson's ratio decrease. The comparison results between the simulated and experimental data demonstrated that the MD simulations can accurately predict the thermal and mechanical properties of ESO-based thermosets. This study gains insight into the variation in thermo-mechanical properties of anhydride-cured ESO/DGEBA-based epoxy resins during the cross-linking process and provides a rational strategy for optimizing bio-based epoxy resins.

Fabrication and Application of Grinding Wheels with Soft and Hard Composite Structures for Silicon Carbide Substrate Precision Processing.

In silicon carbide processing, the surface and subsurface damage caused by fixed abrasive grinding significantly affects the allowance of the next polishing process. A novel grinding wheel with a soft and hard composite structure was fabricated for the ultra-precision processing of SiC substrates, and the grinding performance of the grinding wheel was assessed in this study. Different types of gels, heating temperatures, and composition ratios were used to fabricate the grinding wheel. The grinding performance of the grinding wheel was investigated based on the surface integrity and subsurface damage of SiC substrates. The results showed that the grinding wheel with a soft and hard composite structure was successfully fabricated using freeze-dried gel with a heating temperature of 110 °C, and the component ratio of resin to gel was 4:6. A smooth SiC substrate surface with almost no cracks was obtained after processing with the grinding wheel. The abrasive exposure height was controlled by manipulating the type and ratio of the gel. Furthermore, the cutting depth in nanoscale could be achieved by controlling the abrasive exposure height. Therefore, the fabrication and application of the grinding wheels with soft and hard composite structures is important for the ultra-precision processing of large-size SiC substrates.