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As trapping sites for surface charges, the surface trap is an important factor affecting the insulation performance of the epoxy–SF6 interface, which is closely related to the microstructure and its evolution. However, existing studies often ignore the effect of the degradation of the epoxy surface on the surface traps and charge accumulation during the long-term service of the insulation system. In this study, the surface physicochemical evolution and its influence on surface traps of a typical epoxy–SF6 insulation structure were researched under a DC-temperature gradient condition, and an evolution mechanism of surface traps was proposed. The results show that the free radicals introduced during the material degradation process increase the density and depth of both positive and negative charge traps on the epoxy surface. The effect of free radicals formed by the cleavage of epoxy molecules on the electronic orbital and molecular electrostatic potential of epoxy molecules is the intrinsic reason for the evolution of surface trap evolution. This work may help to understand the long-term evolution mechanisms of the physicochemical characteristics of the epoxy–SF6 interface in DC field and may provide a theoretical basis for the long-term failure mechanism revealing and the insulation performance enhancement. [ABSTRACT FROM AUTHOR]

This research examines the performance of epoxy, ceramic, and graphene coatings on stainless steel 316 in a producer gas environment, focusing on corrosion and erosion resistance. This research aimed to identify the most effective coating for applications in harsh gasification environments. In this research, various analyses, including microstructural examination, hardness and weight measurements, FESEM analysis, and EDAX analysis, were conducted to evaluate the performance of the coatings. The producer gas was passed on to all the coated samples for a period of 100 h. The significant findings include the superior corrosion and erosion resistance of ceramic-coated stainless steel, as evidenced by low weight fluctuations, maintained hardness levels, and elemental stability. Graphene coatings exhibit high hardness but increased porosity, raising concerns about durability, while epoxy coatings are vulnerable to gas-induced structural alterations. The inclusion rating analysis underscored the ceramic coatings’ ability to preserve consistent material properties. Overall, ceramic coatings have emerged as the preferred option for gasification environments due to their structural resilience, inclusion integrity, and elemental stability. Considering the inclusion integrity, mechanical strength, weight stability, and elemental stability, ceramic-coated stainless steel 316 samples exhibit better resistance toward producer gas influence. This research contributes valuable insights for material selection in applications exposed to harsh gasification environments, emphasizing the importance of coating selection for long-term durability and performance.

Various peel-off experiments can be used to determine the adhesion strength of various fibres. Among them was the ‘T’ type peel-off test, which measures the adhesions between fibres. The use of organic and inorganic fillers in flake or powder form will alter the adhesive properties of the binders as well as the adhesive strength between the fibres. In this study, the adhesion strength between three different varieties of glass fibres (C-Glass, E-Glass, and S-Glass fibres) with a PLA core has been investigated. As a binder, an epoxy resin was used, and the resin was modified with inorganic additives such as alumina, bentonite, and silicon carbide. Peel-off testing was used to examine the effect of additives on the bonding strength between a thermoplastic core and a synthetic fibre. The addition of inorganic compounds was found to reduce the adhesion strength between the fibres and the core. In order to evaluate the initial adhesion between the filaments and the core, nine specimens were fabricated without the addition of any additives and their strengths were determined. Maximum adhesion strength of 71.8 MPa was recorded for the neat resin. The adhesive strength after inclusion of additives was observed to decrease by 18.14%, and recorded maximum peel-off strength of 58.2 MPa. Also, the inclusion percentages of the additives were found to be the most influential factor in determining the composites’ adhesive properties. Validation tests were also conducted with the optimized results which demonstrated that the predicted and experimental results were in excellent agreement. Macro and micro approaches were employed to analyze the deformation mechanisms in order to gain a comprehensive understanding of how the additives affected the adhesion strength.

Shape memory polymers (SMPs), although offer a suite of advantages such as ease of processability and lower density, lag behind their shape memory alloy counterparts, in terms of mechanical properties such as recovery stress and cyclability. Reinforcing SMPs with inorganic nanowires and carbon nanotubes (CNTs) is a sought-after pathway for tailoring their mechanical properties. Here, inorganic nanowires also offer the added advantage of covalently binding the fillers to the surrounding polymer matrices via organic molecules. The SMP composites (SMPCs) thus obtained have well-engineered nanowire-polymer interfaces, which could be used to tune their mechanical properties. A well-known method of fabricating SMPCs involving casting dispersions of nanowires (or CNTs) in mixtures of monomers and crosslinkers typically results in marginal improvements in the mechanical properties of the fabricated SMPCs. This is owed to the constraints imposed by the rule-of-mixture principles. To circumvent this limitation, a new method for SMPC fabrication is designed and presented. This involves infiltrating polymers into pre-fabricated nanowire foams. The pre-fabricated foams were fabricated by consolidating measured quantities of nanowires and a sacrificial material, such as (NH4)2CO3, followed by heating the consolidated mixtures for subliming the sacrificial material. Similar to the case of traditional composites, use of silanes to functionalize the nanowire surfaces allowed for the formation of bonds between both the nanowire-nanowire and the nanowire-polymer interfaces. SMPCs fabricated using TiO2 nanowires and SMP composed of neopentyl glycol diglycidyl ether and poly(propylene glycol) bis(2-aminopropyl ether) (Jeffamine D230) in a 2:1 molar ratio exhibited a 300% improvement in the elastic modulus relative to that of the SMP. This increase was significantly higher than SMPC made using the traditional fabrication route. Well-known powder metallurgy techniques employed for the fabrication of these SMPCs make this strategy applicable for obtaining other SMPCs of any desired shape and chemical composition. [ABSTRACT FROM AUTHOR]

The practical application of superhydrophobic coatings has been greatly restricted due to the complicated preparation and fragile hierarchical structures on the surface. In this study, we prepared a robust superhydrophobic coating with a double-layer structure via a low-cost and facile method, adhering the non-wettability layer composed of silica nanoparticles and fluorine-modified epoxy resin to a binder resin layer on aluminum. The fluorine-modified epoxy resin with low surface energy can fix the silica nanoparticles after curing and cross-link with the adhesive layer. When the SiO _2 content in the surface layer is 40%, the water contact angle (WCA) of the coating is 162°, and the sliding angle (SA) is 2°. In the mechanical performance test, the durable coating can remain superhydrophobic even after 260 cycles of friction or 160 cycles of tape peeling. In addition, the superhydrophobic coating with self-cleaning and anti-fouling properties also has the performance of acid-base solution resistance. Hence, the combination of the rough layer and the adhesive layer makes the practical application of artificial superhydrophobic coatings possible.

In this research, carbon fiber and Graphene nanoplatelets (GNP) of different weight percentages of GNP (0, 0.1,0.3, and 0.5 wt%) reinforced hybrid composites were fabricated via hand layup technique followed by compression molding. For wear analysis to understand the correlation between control parameters (wt% of filler, normal load, velocity, and sliding distance) and response measurements (weight loss), the design of experiments and analysis of variance (ANOVA) is used. The control variables such as normal loads (5, 10, 15, and 20 N), velocity (1, 2, 3 and 4 m s ^−1 ), and sliding distance (200, 300, 400, and 500 m) are selected for the research. It was observed that 0.5 wt% GNP-filled carbon fiber/epoxy composite shows higher tensile and flexural strength than another composite. It has been discovered that adding GNP reduces the wear in terms of weight loss. Scanning electron microscopy (SEM) was used to examine composites’ worn surfaces. The analysis concluded that experimental results are closer to optimum results.

Flexural response of crump rubber filled epoxy composites is reported in the present work. Composites are fabricated using open mold casting technique and test specimens are evaluated at normal strain rate. Stress strain profiles of all the specimens reveal brittle mode of fracture. Modulus of crump rubber composites increase with increasing crump rubber content owing to good bonding of constituents and higher elasticity induced by crump rubber particles. Neat epoxy specimens reveal lower modulus than all the composites filled with crump rubber. Strength of all the composites are higher as compared with neat epoxy and increase as the crump rubber content is increased. Composites filled with 30 vol% of crump rubber reveals highest modulus (24%) and strength (22%) in comparison with neat epoxy and all other compositions. Scanning electron microscopy of specimens are analyzed to study the structure property correlations. Mapping of results from the current work and existing ones are compared using property chart.

This paper evaluates the wear properties of epoxy nanocomposites containing GNP (Graphene Nanoplatelets). In this research, variation of GNP (0,0.1, 0.25, and 0.5 wt%) were used to make nanocomposites. The hand layup technique was used for the fabrication of different composites. The Taguchi method is used to optimize the wear test and its related characteristics. Analysis of variance is used to understand the correlation between input variables and response measurements. Load (0.5, 1.0, 1.5, and 2.0 kg) and time (4, 6, 8, and 10 min) are the main variables for exploring wear characteristics for this study. It has been discovered that minimum wear in terms of mass loss and friction coefficient are minimum at 0.5 wt% GNP. Scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), and RAMAN spectroscopy were used to characterize the wear mechanism. The result shows that the optimized value is closer to the experimental value.

The current research explores the possibility of reinforcing massively available, less utilised, low-cost agro-residue fibres in an epoxy matrix to create a new tribo-material. This study focuses on determining the three-body abrasive wear behaviour (volume loss and specific wear rate (SWR)) of natural cellulosic pigeon pea (PP) stalk fibre reinforced epoxy composites. Further, abrasive wear characteristics of untreated and treated E/PP20 (20 wt.% PP stalk fibre-reinforced epoxy) composites were analysed using Taguchi and ANOVA techniques. Untreated and treated biocomposite specimens were developed using the hand lay-up (open mould) technique. At 11.77 N, 23.54 N, and 47 N loads, the SWR of untreated E/PP20 composite was reduced by almost 5.03%, 3.68%, and 22.30% compared to epoxy specimens. Results of the untreated E/PP20 composite showed that the applied load was the main contributing parameter (54.72%), followed by sliding distance (21.82%) and sliding speed (15.31%). Results of the treated E/PP20 composite showed that the applied load was the main contributing parameter (48.96%), followed by sliding speed (26.24%) and sliding distance (20.78%). The regression model predicted the SWR with a pooled error ranging from 2.37% to −17.77% for untreated composite and 9.87% to −11.49% for treated composite, respectively. The alkali-treated E/PP20 composite exhibited better abrasive resistance than the untreated E/PP20 composite. Scanning electron microscopy images of the treated composites showed good fibre adhesion with the matrix. In addition, the surface of the treated composite showed no fibre pullout or ploughing compared to that of the untreated composite. Surface topography revealed the formation of more craters on the surfaces of the untreated composites and small-sized dispersed craters on the treated composites.

Composite sandwich structures are widely used in a multitude of fields owing to their excellent properties, such as light weight and high strength. In this study, a series of hexagonal-core sandwich panels were integrally fabricated by three-dimensional (3D) printed continuous fiber reinforced thermosetting epoxy composites. The influence of the scaling effects that is, the side length and layer thickness on the compression performance of these structures was studied. The experimental results showed that the specific strengths of three different hexagonal-core sandwich panels with different side lengths of 5 mm, 10 mm and 20 mm side lengths is roughly maintained at 0.018 MPa/(kg m ^−3 ). In addition, doubling the wall thickness of the hexagonal core increases the compressive strength by only 38.9%. The performance characteristics of these hexagonal-core sandwich panels, which change with size, can provide a reference for designers and can be used for the preliminary prediction of the structural strength.

Epoxy and its composites have shown remarkable properties to be used for outdoor high voltage insulation applications. However, outdoor environment that contains UV-A radiations deteriorates the organic structure of epoxy-based insulators. To analyze the surface degradation and chemical changes in structure due to UV radiations, neat epoxy (NEPOX), 15 wt.% epoxy microcomposite (EMC 15) and 5 wt.% epoxy nanocomposite (ENC 5) were prepared and subjected to a specially fabricated UV chamber under accelerated conditions. The samples were analyzed with visual inspection, STRI hydrophobicity classification, and Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The analyses confirmed the pattern of gradual degradation of surface structure due to the appearance of ester and carbonyl groups due to oxidation of hydrocarbon chains. FTIR peaks of C=O stretching at ∼1725.52 increased by 157.44%, 75.86% and 33.33% for NEPOX, EMC 15 and ENC, respectively. This shows that ENC-5 expressed better resistance against surface oxidation as compared to EMC 15 and NEPOX. Addition of fillers enhanced the chain intactness and nano filler performed even better due to greater surface area and surface energy.

Tensile test is conducted on environmentally pollutant crumb rubber/epoxy composite. Crumb rubber particles with different volume fractions (10, 20 and 30%) are reinforced with epoxy matrix. Stress-strain curves reveal brittle fail for all the samples. Crumb rubber filled epoxy composites reveal higher modulus (13%–28%) and strength (28%–44%) than neat epoxy sample. Epoxy with 30 volume % of crumb rubber depicts higher modulus and strength compared with all other compositions, exemplifying use of crumb rubber for utilarian applications. Crumb rubber/epoxy composites register higher specific modulus and strength for all compositions in comparison with neat epoxy. Scanning electron micrographs of test samples are used to analyze property - composition correlations. Finally, property map is plotted to compare the results of present study with existing ones to highlight the efficacy of the proposed composites.

Natural fibers gain acceptance in various applications due to their advantages over synthetic materials especially in terms of environmental impact, lightweight feature, availability and cost. Apparently, a natural fiber that still needs further exploration on its use in composite is salago. In this study, untreated and alkaline treated salago fiber with varying number of layers from one to three sheets were reinforced in epoxy resin. FTIR analysis and optical microscopy were used to analyze the effect of 5 wt. % sodium hydroxide treatment on the fiber sheets. On the other hand, the composites were subjected to tensile, flexural and Izod impact tests. Tensile fracture morphology was observed through FESEM while thermal degradation was evaluated using thermogravimetric-differential thermal analysis. As compared to neat epoxy, improvements on tensile (52.8%), flexural (37.6%) and impact (more than 6 times) strengths were obtained for the composite with three layers of untreated fiber sheets. Generally, the mechanical properties of the composites improved as the fiber sheets increases. However, the alkaline treated fiber composites obtained lower strengths than their untreated counterparts which may be associated to the presence of holes on the fiber sheets caused by the chemical treatment. Nevertheless, enhancements on moduli and thermal stability were still achieved for the composites with treated fibers which could be related to the good fiber-matrix adhesion caused by the partial removal of hemicellulose and lignin. Moreover, the composite can be used in applications that require high impact strength and stiffness like frame for drones or robots.

The present work focused on electromagnetic (EM) absorption performance comparison of different polymer nanocomposite structures. Synthesis and fabrication of polymer nanocomposite composed of graphene, polyurethane (PU), epoxy was done using in situ polymerization and resin transfer moulding respectively. The effect of polymer on EM properties of composite was carried out using waveguide measurement technique in X-band. Reflection Loss (RL) and shielding effectiveness (SE) were measured for various nanocomposites using EM wave theory. From the results it is observed that 2.5 wt% of PU/epoxy graphene nanocomposite has shown RL value −35 dB at 12.1 GHz and SE value of −45 dB.

This work examines the impact of artificial aging on tensile and flexural behavior of epoxy-nanoclay composites (ENCs) and glass fiber-epoxy-nanoclay composites (GFENCs) in the hygrothermal chamber. Epoxy-nanoclay composites made by a general-casting technique, and GFENCs are made by hand layup technique. The specimens are aged in the hygrothermal chamber for 180 days at 40 °C with 60% RH. The results revealed that an increase in nanoclay and glass fiber weight percentage enhanced the mechanical behavior of GFENCs. The aging of the sample has a negative influence on the composite materials. But, the increase in nanoclay and glass fiber weight percentage has diminished the impact of aging on the mechanical behavior of composites. SEM micrographs revealed the reason for the failure and influence of aging conditions.

Ionic liquids are promising candidates with huge potential in combination with thermosetting polymers. However, the behavior of ionic liquid modified epoxy system towards outdoor environmental conditions are seldom reported. Therefore, it is interesting to study the effect of accelerated weathering on ionic liquid modified bioepoxy blends. In this work, bio-based epoxy resin and 1-Butyl-3-methylimidazolium chloride (BMIM[Cl]) ionic liquid blends were prepared by melt mixing method. The concentration of ionic liquid used was 0, 5, 10, 20, and 30 phr. The miscibility, morphology, thermo-mechanical, and surface hydrophilicity of the ionic liquid modified bioepoxy blends were studied before and after the accelerated weathering test. The miscibility of the blends was studied by Fourier transform infrared spectroscopy (FTIR). The FTIR results demonstrate the presence of charge transfer complexation reaction between ionic liquid and bioepoxy resin. The tensile strength and modulus were reduced while the elongation at break is increased with the addition of ionic liquid. On the other hand, the glass transition temperature and thermal stability of the bioepoxy blends were reduced with the addition of ionic liquid. The contact angle value increases with the incorporation of up to 10 phr ionic liquid, this is followed by a decrease. The interaction between the ionic liquid and bioepoxy resin has vanished after the weathering test. The elongation at break was reduced dramatically after the weathering test, especially for 20 and 30 phr blends. The thermal stability of the weathered samples is similar to that of the samples before weathering. While the T _g values of the blends are stable with respect to neat bioepoxy resin. On the other hand, the contact angle value of the bioepoxy blends increased after the weathering test due to the increased surface roughness after weathering.

The hollow glass microsphere (HGM)/carbon nanotubes (CNTs)/epoxy composite foam are fabricated by solution casting of functionalized CNT and functionalized HGM-epoxy dispersion. Five weight ratio configurations (2, 4, 6, 8, and 10 wt%) of functionalized–HGMs were considered and compared with 0.1 wt% CNT/epoxy to investigate the effects of hollow micro sphere enrichment. This study investigate the effect of hollow glass microspheres (HGM) on the compressive strength and storage modulus of CNT modified epoxy resin. The results revealed that the incorporation of HGM improved the damping performance evidently and broadened damping temperature range. TEM image of the composite show a better dispersion of CNTs in epoxy matrix. SEM micrographs of composite foams are investigated to determine structure development and CNTs, HGM dispersion, with regard to experimental results, especially compression test.

The current research work focused on the abrasive wear behavior of the basalt fabric as reinforcement in epoxy and polyester composites. Traditional hand-layup technique is used to manufacture the composites. The mechanical characteristics of the basalt fiber reinforced composites have been reported. The two body abrasive wear behavior of the fabricated composites was conducted by using pin/ball on disc tester TR-20 disc equipment. Test were conducted at two different load of 5 N and 10 N, for various sliding distances of 25 m to 100 m at equal intervals with 400 grade grit of particle size 35 μm. Wear resistance of the composites were determined by calculated the specific wear rate of the composites. Basalt fiber as reinforcement in epoxy composites showed better wear resistance than basalt fiber as reinforcement in polyester composites. Wear mechanism of worn samples is conducted by using the Scanning Electron Microscopy (SEM).

Strategies are suggested for the waste utilization of industrial leather by preparing composites with epoxy and high-density polyethylene (HDPE). The addition of leather improves the average specific compression toughness of epoxy by 29%. The fracture surface analysis suggests the incorporation of leather microparticles leads to a transition of failure mode of epoxy from brittle to ductile. In addition, the dynamic strength of the leather/epoxy composite is found to be 69% higher than that of neat epoxy. However, no significant changes are observed when HDPE is infiltrated with leather. Apart from dispersing the leather particles directly in polymer, a novel strategy is presented here in which leather/HDPE microfibers are prepared and then used to reinforce the epoxy matrix. The specific compression modulus of this composite blend is 8% and 65% higher than epoxy and HDPE, respectively. Fractography is further carried out on the failed specimens to understand the failure mechanism in each composite. A change in the failure mode is observed when epoxy is reinforced either with leather particles or the microfiber. While the failure strength of the microfiber is found to be higher than epoxy, the strength of microfiber/epoxy interface is lower than that of epoxy.

Epoxy decays its dielectric characteristics and exhibits degradation of main hydrocarbon on exposure to multiple environmental stresses. Inorganic oxides-based epoxy composites have been performingwell in many applications and short-term testing; therefore, evaluation of their dielectric and structural characteristics under extreme weathering conditions may also unleash enhancement in these characteristics. To explore dielectric properties and degradation of main hydrocarbon group, neat epoxy and silica-based epoxy microcomposite (15% micro-silica loading) and nanocomposites (5% nano-silica loading)have been prepared and subjected to acid rain, heat, ultra-violet radiation, salt fog, and humidity in a chamber that was specially fabricated in view ofservice conditions. Interesting results were obtained before and after aging. Enhanced intactness of methylene group was observed in nanocomposite followed by micro composite. Similarly, for epoxy nanocomposites not only higher dielectric constant, lower energy dissipation and conductivity was recorded before application of stresses, but also nanocomposite showed superior sustainability in these properties after aging. In all analyses, microcomposites performed better than neat epoxy but in conductivity the results of both samples were found comparable.