Epoxy Surface Research Articles

New star-like polydimethylsiloxanes: synthesis, properties, and application

New star-like polydimethylsiloxanes with a cis-tetraphenylcyclotetrasilsesquioxane fragment as the core (branching center) were synthesized and characterized. The thermophysical properties of the obtained polymers were studied by DSC and TGA. The epoxy resin surface modified with the obtained polymers was analyzed by XPS.

Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography

Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF3.ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute’ differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5′-monophosphates, and weak bases, e.g., nucleobases and nucleosides.

Voltammetric Characterization of Nickel Hydroxide Grown on Nickel+Epoxy Mouldable Electrodes

The structure and electrochemistry of the nickel hydroxide have been studied extensively because of its importance in different technical processes, such as oxygen electro-catalysis, as the active material in nickel battery systems, as electrochromic material and capacitor applications . On the other hand, so as to make use of nickel-oxide electrodes as electrochemical capacitors, a high specific area is necessary for increasing the amount of stored energy. In recent years a great technical achievement has been the preparation of composite materials since these materials are characterized by a controlled degree of porosity. Special interesting result in particular those made up of conductive powders (i.e. nickel, graphite, graphene, nanotubes, etc.) dispersed in an insulating polymeric matrix. With an appropriate percentage of conductive powders, they have a good electrical conductivity and a high developed electro-active surface. Also, a high ionic conductivity is required to allow the electrolyte to penetrate inside the porous network. Nickel hydroxide layers can be prepared by different methods. In basic solutions, the redox processes involving nickel hydroxide and oxi-hydroxide can be described as:NiOOH lattice Ni(OH)2 lattice Nickel+epoxy composites were elaborated by dispersing nickel powder in a polymeric matrix of epoxy resin. Nickel hydroxide was generated on nickel+epoxy surfaces as well as on polycrystalline nickel by means of successive voltammetric cycles and a galvanostatic reduction [2]. The electrochemical response was studied in KOH solutions at several concentrations. Nickel hydroxides grown on nickel+epoxy surfaces exhibit a different potentiodynamic i-E profile and cathodic charges which are largely affected by nickel/epoxy ratio, potential sweep rate and pH solution. The results revealed that both Ni(OH)2 and NiOOH present at least, two structural modifications, named a and b in the case of the Ni(OH)2 while they are designed as g and b in the case of NiOOH. The a-Ni(OH)2 structure is unstable in KOH concentrated solutions and it progressively transforms into b-Ni(OH)2, leading to the 50-70 mV positive shift of the anodic peak observed when the electrode is cycled or is allowed to stay in concentrated KOH solutions. Also, during cycling and specially when in a strong alkaline medium, the irreversibly turns into the more expanded . This phase change can be correlated to a 44 % increase in volume, causing mechanical deformation which results in an irreversible damage to the electrode. According to Barnard and Randell [1] the following redox processes can be found: ; and at slightly more positive potentials.This work is focused on the substrate effect over the ability to accumulate charge and the oxygen evolution reaction, comparing them with those obtained by using polycrystalline nickel [2], in order to further application in power sources and the oxygen evolution electrocatalysis [3]. In these growth conditions, the “coulommetric porosity” of electrodes reveals as a characteristic value related to the structure of nickel+epoxy used as a substrate. At more concentrated solutions, the longer penetration depth of nickel hydroxide inside the porous network of nickel+epoxy leads to higher cathodic charges. However, the ability to accumulate charge is drastically reduced when nickel weight percentage was of 80% wt, even in KOH concentrated solutions. The different potentiodynamic i-E profile of nickel hydroxides grown on nickel+epoxy from those grown on polycrystalline nickel is attributed to a-Ni(OH)2 stabilization, as a consequence of pH-decrease inside the porous network, having adverse effects on the oxygen evolution. This fact and the higher accumulated charges at concentrated solutions make these electrodes of 87%wt covered with a-Ni(OH)2 the most suitable for batteries applications. Table 1. Ni(OH)2 grown on different electrodes, Qcat = cathodic charge calculated at v = 50 mV·s-1, ρ coulometric roughness. 1 M KOH. T = 298 K Qcat (mC) ρ Polycrystalline Ni 1.5 - 87 wt% nickel-epoxy 31 0.82 80 wt% nickel-epoxy 0.25 0.75 REFERENCES [1] R. Barnard, C.F. Randell, F.L. Tye, J. Appl. Electrochem. 10 (1980) 109. [2] J. Agrisuelas, C. Gabrielli, J.J. García-Jareño, D. Giménez-Romero, J. Gregori, H. Perrot, F. Vicente, ECS Transactions, 6 (24) 79-95 (2008).[3] J.A. Bastos, M.R. Barbosa, J. Gregori, J.J. García-Jareño, F. Vicente, ECS Transactions 6(8) 229-245 (2007).ACKNOWLEDGEMENTS Part of this work was supported by FEDER-CICyT CTQ2015-71794-R.

Superhydrophobic epoxy coating modified by fluorographene used for anti-corrosion and self-cleaning

A facile method for the fabrication of organic coating with superhydrophobic surface on copper substrate is presented in this paper. Liquid-phase exfoliated fluorographene (FG) nanosheets, a low-surface-energy material with different sizes and shapes, are spatially stuck on the surface of epoxy resin coating to build rough surface with random micro/nano structure. The built coating system displays superior protection performances due to its self-cleaning function, mechanical abrasion resistance and chemical stability both in acidic and alkaline aqueous solutions. It not only provides a facile process for superhydrophobic modification of organic coating, but also introduces a new and effective strategy to protect materials by synergistically coupling the protection function of both superhydrophobic surface and organic coating, which can be used for large-scale manufacturing of superhydrophobic organic coating in industrial applications.

Metastable Liquid Cavitation Control (With Memory) Apparatus, Methodology, and Results: For Radiation Detection, Reactor Safety, and Other Industrial Applications

We present a method to simultaneously pressurize fluid filled containers from outside and within, results of experiments with temporary 2 h of fluid precompression followed by overpressure removal before testing for cavitation strength and sensitivity to neutron radiation of multi-mL quantities of widely used unfiltered and undegassed liquids, such as water, ethanol, and dodecane (a surrogate jet fuel), enclosed within containers using glass, epoxy, and steel. We found that in contrast to prior methods involving laborious degassing and purification, a straightforward one-step approach using only a modest 2 h precompression treatment at a pressure of 0.7+ MPa enabled us, reproducibly, to reach directly the highest attainable “negative” (subvacuum) pressures attainable in our apparatus (−0.7 MPa)—enabling efficient sensitivity to neutron-type radiation. Cavitation strength results are explained on theoretical grounds. However, surprisingly using the technique of this paper, the 2-h precompressed (unfiltered, undegassed) fluid also retained memory of this property, after the overpressure was removed, even 3 months later—thereby suggesting that active cavitation nuclei suppression can be extended to long periods of time. Successful results for cavitation suppression (in the absence of ionizing radiation) through −0.7 MPa were also attainable for fluids in simultaneous contact with a combination of glass, steel, and epoxy surfaces. The relative importance of cavitation strength retention at liquid–wall interfaces versus within the bulk of the fluids is reported along with implications for high-efficiency nuclear particle detection and spectroscopy, and nuclear fission water reactor safety thermal-hydraulic assessments for blowdown transients.

Resistance of surface fluorinated epoxy resin to corona discharge in SF<inf>6</inf> gas

Our previous results have shown that direct fluorination can modulate surface electrical properties and suppress surface charge accumulation of epoxy insulators, and thus has potential applications for improving the flashover performance of epoxy spacers in gas-insulated equipment. In this study, to investigate the resistance of the fluorinated epoxy surface layer to partial discharge in SF 6 gas, surface fluorinated epoxy samples together unfluorinated (virgin) ones were corona treated using a multi-needle-to-plate electrode system. ATR-IR analyses and SEM surface and cross section images show that the corona discharge caused the chemical modification and chain scission at some weak points in the fluorinated layer and the crosslinking reaction, and thus led to the formation of nodules on the corona treated fluorinated surface. However, the corona treatment did not change the fluorinated layer thickness. In contrast with this, severe degradation, most likely in the form of etching, occurred for the virgin surface layer during the same treatment. Measurements of surface potential decay and water contact angle indicate that the corona discharge obviously reduced surface conduction of the fluorinated sample, and rendered the surface conduction insensitive to humidity although the corona treatment almost did not change surface wettability of the fluorinated sample. On the contrary, the measurements show that surface conduction of the virgin sample increased and became sensitive to humidity after the corona treatment.

Effects of the media and ageing condition on the tensile properties and fracture toughness of epoxy resin

This paper presents the water diffusion behaviour, tensile properties and fracture toughness of epoxy after it is aged in distilled and salt water in both steady and fluctuating conditions at a temperature of 50 °C. In steady and fluctuating conditions, the equilibrium water uptake of epoxy aged in salt water is lower than that in distilled water, but the diffusion rate is unaffected. The effects of the media and ageing condition on the tensile properties and fracture toughness are insignificant. The absorbed water (0.6–1.8%) improves the epoxy fracture toughness up to three times, which is indicated by the complex fracture surfaces of aged epoxy.

Quantification of antibody coupled to magnetic particles by targeted mass spectrometry

Quantifying the amount of antibody on magnetic particles is a fundamental, but often overlooked step in the development of magnetic separation-based immunoaffinity enrichment procedures. In this work, a targeted mass spectrometry (MS)-based method was developed to directly measure the amount of antibody covalently bound to magnetic particles. Isotope-dilution liquid chromatography-tandem MS (ID-LC-MS/MS) has been extensively employed as a gold-standard method for protein quantification. Here, we demonstrate the utility of this methodology for evaluating different antibody coupling processes to magnetic particles of different dimensions. Synthesized magnetic nanoparticles and pre-functionalized microparticles activated with glutaraldehyde or epoxy surface groups were used as solid supports for antibody conjugation. The key steps in this quantitative approach involved an antibody-magnetic particle coupling process, a wash step to remove unreacted antibody, followed by an enzymatic digestion step (in situ with the magnetic particles) to release tryptic antibody peptides. Our results demonstrate that nanoparticles more efficiently bind antibody when compared to microparticles, which was expected due to the larger surface area per unit mass of the nanoparticles compared to the same mass of microparticles. This quantitative method is shown to be capable of accurately and directly measuring antibody bound to magnetic particles and is independent of the conjugation method or type of magnetic particle. Graphical Abstract Schematic illustration of the isotope-dilution mass spectrometry-based workflow to directly measure antibody bound to magnetic particles (MP).

Effects of liquid properties on the dynamics of under-liquid laser-induced shock process

We compared the shock processes induced when focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy resin blocks immersed in glycerol, water, liquid paraffin, and silicone oils. A custom-designed time-resolved photoelasticity imaging technique was applied to observe the strength of stress wave induced inside the solid target and the propagation of shock waves in the liquid with time resolution of nanoseconds. We demonstrated that the shock impedance of the liquid caused a noticeable effect on the strength of laser-induced stress wave: Ablation in the liquid with a higher shock impedance resulted in a stronger stress. By using glycerol instead of water as the confining medium, the pulse energy required to induce a certain level of stress was reduced by about 20 %. The dynamical behaviors of the main shock wave and the reflected wave in inverted V-shape in each liquid are also discussed in details.

Effect of strain rate on the fracture behaviour of epoxy–graphene nanocomposite

In this study, epoxy-based nanocomposite was fabricated by the addition of graphene nanosheet via a solution casting method. To investigate the effect of strain rate on tensile properties of epoxy, tensile tests were done on standard samples at different strain rates (0.05–1 min−1). The role of strain rate and presence of graphene on fracture behaviour of epoxy were also studied by investigation of the fracture surfaces of some samples by scanning electron microscopy (SEM). Finally, Eyring’s model was performed to clarify the role of strain rate on activation volume and activation enthalpy of epoxy. The results of tensile tests showed a maximum strength of epoxy–graphene nanocomposite at the graphene wt% of 0.1%. Tensile strength of epoxy obviously improved with increasing strain rate, but tensile strength of epoxy/graphene nanocomposite sample was less sensitive. Fracture micrographs showed that the mirror zone of the fracture surface of epoxy diminished by increasing strain rate or addition of graphene; and final fracture zone also became rougher. Finally, by investigation of the activation enthalpies, it was showed that much higher enthalpy was needed to fracture the nanocomposite sample, as the activation enthalpy changed from 41.54 for neat epoxy to 67.34 kJ mol−1 for EP–0.1% GNS sample.

Influence of micron size aluminum particles on the aging properties and wear resistance of epoxy resin coatings

Abstract In this work, an unoxidized aluminum particle/epoxy composite coating was used to cover the surface of pure epoxy resin to reduce the loss of strength after water-heat aging and to improve the wear resistance. The samples were maintained in a water bath at 80°C for 100 days to accelerate the aging process. After water-heat aging, the tensile and bending strengths of the pure epoxy samples were reduced from 30 MPa and 60 MPa, respectively, to 26 MPa and 55 MPa, respectively. However, the tensile and bending strengths of the sample with 6 wt.% aluminum particles were reduced from 39 MPa and 95 MPa to 36 MPa and 89 MPa, respectively. The sample with 6 wt.% aluminum particles exhibited the lowest tensile and bending strength loss rates, 7.2% and 6.1%, respectively, which were 37.4% and 40.8% lower, respectively, than those of the pure epoxy. Additionally, the wear rate and friction coefficient of the samples with 6 wt.% aluminum particles were 2.5×10-6 cm3/min·N and 0.415, respectively, corresponding to a reduction of 35.9% and 30.0%, respectively, compared with the pure epoxy. Thus, it was found that the addition of unoxidized aluminum particles can efficiently increase the water-heat aging resistance and wear resistance of epoxy resin.

Characteristics of microsecond-pulse surface flashover on epoxy resin surfaces in SF6

Surface flashover on insulating materials is likely to occur in composite apparatuses in overvoltage situations. In order to investigate the surface characteristics of epoxy resin (EP) materials, before and after flashover, microsecond pulses were applied to simulate transient overvoltage situations in a power system. Within the SF6 filled experimental chamber, pulse voltages with a frequency of 5 Hz and an amplitude of 25 kV were applied to induce surface flashover. The flashover characteristics of EP under different SF6 pressures were subsequently determined. The results show that the flashover voltage increases with increasing SF6 pressure. In addition, atomic force microscopy, scanning electron microscopy, and X-ray energy dispersive spectroscopy were performed to explore the morphology and elemental content of the material surfaces. During aging treatment, granular bulges were generated on the surface of the materials. With increasing treatment time, bulges first gathered and then became larger. Then, they became flattened as a result of burning due to electrical arcing. Thus, the surface roughness increased at first and then decreased. The material surface sequentially evolved into crack, granular, flocculent-granular, and then flocculent zones during the aging process, and these zones were distributed symmetrically in the aging area. Moreover, a large amount of flocculent substances (consisting of carbon and carbon compounds) accumulated near the electrodes. The insulating performance of the material surface was impaired by the aging treatment, which can be attributed to the combined effects of change in surface roughness and the discharge channel generated by surface carbonization.

Pattern Formation by Staphylococcus epidermidis via Droplet Evaporation on Micropillars Arrays at a Surface.

We evaluate the effect of epoxy surface structuring on the evaporation of water droplets containing Staphylococcus epidermidis (S. epidermidis). During evaporation, droplets with S.epidermidis cells yield to complex wetting patterns such as the zipping-wetting1-3 and the coffee-stain effects. Depending on the height of the microstructure, the wetting fronts propagate circularly or in a stepwise manner, leading to the formation of octagonal or square-shaped deposition patterns.4,5 We observed that the shape of the dried droplets has considerable influence on the local spatial distribution of S.epidermidis deposited between micropillars. These changes are attributed to an unexplored interplay between the zipping-wetting1 and the coffee-stain6 effects in polygonally shaped droplets containing S.epidermidis. Induced capillary flows during evaporation of S.epidermidis are modeled with polystyrene particles. Bacterial viability measurements for S.epidermidis show high viability of planktonic cells, but low biomass deposition on the microstructured surfaces. Our findings provide insights into design criteria for the development of microstructured surfaces on which bacterial propagation could be controlled, limiting the use of biocides.

Mechanism Analysis of Stiffness Improvement by Waterborne Epoxy Resin Surface Sizing Agent

Mechanism Analysis of Stiffness Improvement by Waterborne Epoxy Resin Surface Sizing Agent

Water droplet initiated discharges on epoxy nanocomposites under DC voltages

Epoxy nanocomposites with different percentages of nano clay filler are prepared using a shear mixer technique. Corona inception voltage (CIV) due to water droplets on the epoxy nanocomposite is high under negative direct voltage compared with positive polarity voltage. It was found that an increase in droplet volume and number of droplets within the gap reduces the CIV. The magnitude of discharge current flow is high under negative polarity. Surface charge accumulation studies indicate nonlinear variation in distribution of charges on the surface of the epoxy nanocomposite with water droplets. Optical Emission Spectroscopy (OES) results confirm high temperature plasma during water droplet initiated electrical discharges on the surface of epoxy resin. Laser Induced Breakdown Spectroscopy (LIBS) results indicate the presence of carbon on the degraded surface of the sample. The absorbed energy on the sample surface during arcing is measured through leakage current, and is observed to be higher for negative polarity. UHF signals were radiated due to corona discharges from water droplets on the epoxy nanocomposites under direct voltages and their bandwidth is in the range of 1–2 GHz.

Detecting debonding flaws at the epoxy–concrete interfaces in near-surface mounted CFRP strengthening beams using the impact–echo method

This paper discusses the feasibility of using the impact–echo method (IE method) to assess the debonding flaws at the epoxy–concrete interfaces of near-surface mounted carbon fiber reinforced polymers (NSM CFRPs). The effectiveness of NSM CFRP strengthening is influenced by whether epoxy bonds CFRP bars and existing concrete structures effectively and thoroughly, thereby mutually transmitting the stress in the reinforced zones with CFRP bars. Because of poor construction quality, aging, and deterioration, debonding occurs between epoxy and concrete surfaces, severely inhibiting the reinforcement effectiveness of NSM CFRPs. The IE method is based on the principle of stress waves and was adopted in this study as the nondestructive debonding flaw assessment technique. To clarify the characteristics of the stress wave propagation caused by impact forces on NSM CFRP structures, numerical analysis and experimental test were performed on the bar-like epoxy specimens with a cross-sectional size of 13×13mm. The types of specimens used in this study included the bar-like pure epoxy specimen, bar-like epoxy specimens containing CFRP bars, and the concrete beams containing bar-like epoxy specimens with and without CFRP bars. For the concrete beams embedded with bar-like epoxy specimens, various debonding statuses at the epoxy–concrete surfaces were considered. The numerical analysis revealed that the impact responses in the bar-like pure epoxy specimen and bar-like epoxy specimens containing CFRP bars were dominated by the first few cross-sectional modes of vibration, and the IE test verified this result. The numerical and experimental results indicated that for the concrete beams containing bar-like epoxy specimens with and without CFRP bars and without debonding flaws, the impact response spectra each featured one high-amplitude peak at the fundamental mode frequency, referred to as the dominant frequency. When debonding occurred at the epoxy–concrete interfaces of the concrete beams containing bar-like epoxy specimens with and without CFRP bars, the impact responses showed that the dominant frequencies decreased significantly. When the dominant frequencies instead increased to levels nearly equal to those of the fundamental frequencies of the bar-like epoxy specimens, the epoxy thoroughly debonded from the concrete interfaces. According to the characteristics of the aforementioned impact responses, the IE method is capable of detecting the debonding flaws at epoxy–concrete interfaces in NSM CFRP strengthening.

Effects of nano-silica contents on the properties of epoxy nanocomposites and Ti-epoxy assembles

In order to get a strong Ti-epoxy bond, nano-silica was added to epoxy as the reinforcement, and the effects of the presence of nano-silica on the properties of epoxy nanocomposites and Ti-epoxy assembles were investigated. The results showed that, although glass transition temperature of nanocomposites decreased with the increase in silica addition, mechanical properties of the nanocomposites such as flexural strength, fracture toughness, and hardness rose to the highest values when silica content was 15 wt%. However, the shear strength of the Ti-epoxy assemble was 45.38 MPa when the silica content was 2.5 wt%, from a low of 31.75 MPa for pure epoxy bonded assemble, increasing by 42.9%. With further increase in silica content, the shear strength decreased gradually. The remarkable increase in the shear strength with 2.5 wt% silica addition should be attributed to the improved wettability between epoxy and Ti surface, which resulted in much higher bonding strength between them.

Effect of superheated steam treatment of carbon fiber on interfacial adhesion to epoxy resin

To elucidate the effect of superheated steam (SHS) treatment of carbon fiber on the adhesion to epoxy resin and surface states, virgin unsized carbon fiber was exposed to SHS with or without N2 in the temperature range of 500–800°C. The interfacial shear strength (IFSS) between the carbon fiber and epoxy resin was successfully improved by SHS treatment with N2, and the IFSS of fiber treated above 700°C was the same as or higher than that of a commercial sized fiber. SHS treatment without N2 resulted in an increase of total acidic groups on the fiber surface accompanied with the increase of phenolic hydroxyl groups, whereas that with N2 resulted in a simultaneous increase of total acidic and basic functional groups. The significant improvement in the IFSS after SHS treatment with N2 is considered to be due to the increase of basicity on the fiber surface.

Aging Characteristics on Epoxy Resin Surface Under Repetitive Microsecond Pulses in Air at Atmospheric Pressure**supported by the Natural Science Foundation of Hebei Province (No. E2015502081), National Natural Science Foundation of China (Nos. 51222701, 51307060), and the National Basic Research Program of China (No. 2014CB239505-3)

Research on aging characteristics of epoxy resin (EP) under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvoltage always occurs in a power system, which causes flashover and is one of the main factors causing aging effects of EP materials. Therefore, it is essential to obtain a better understanding of the aging effect on an EP surface resulting from flashover. In this work, aging effects on an EP surface were investigated by surface flashover discharge under repetitive microsecond pulses in atmospheric pressure. The investigations of parameters such as the surface micro-morphology and chemical composition of the insulation material under different degrees of aging were conducted with the aid of measurement methods such as atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with the accumulation of aging energy on the material surface, the particles formed on the material surface increased both in number and size, leading to the growth of surface roughness and a reduction in the water contact angle; the surface also became more absorbent. Furthermore, in the aging process, the molecular chains of EP on the surface were broken, resulting in oxidation and carbonisation.

Impact of Increased Temperature on Cohesiveness of Textile Glass Reinforcement with UHPC Matrix

The contribution is focused on research results of thin elements with UHPC matrix reinforced by textile glass reinforcement. A set of three test samples with size of 1100 x 120 x 20 mm were produced in laboratories of the Klokner Institute. Using accompanying tests the material characteristics of the concrete matrix and the textile glass reinforcement were determined. This reinforcement is modified by a protective epoxy surface layer, co called coating. The reason of the coating is to prevent a formation and a development of corrosive processes on the reinforcement texture. The samples were tested at four-point bend test in a thermal chamber. The thermal chamber is a space where it is possible to gradually regulate the temperature up to 75 °C under a constant value of a loading. In the course of the temperature increasing is using a measuring unit measured mainly bend in the middle of the span in time and the course of an inner and outer temperature. The impact of the increased temperature on the cohesiveness of the non-conventional reinforcement and the UHPC matrix is evaluated from the monitored data.