Epoxy Binder Research Articles

Curing-induced internal stress in epoxy coatings: Effects of epoxy binder, curing agent, filler, initial solvent concentration, curing temperature, and relative humidity

Curing-induced internal stresses in epoxy coatings are highly influenced by the type and concentration of product ingredients and the conditions applied. In this work, the effects on the curing-dependent modulus and the internal stress development of the epoxy/crosslinker chemistry, curing temperature, relative humidity, filler conditions, and initial solvent concentration, are studied. Analytical methods include the attenuated total reflection-Fourier transform infrared (ATR-FTIR) technique, dynamic mechanical thermal analysis (DMTA), a 3D optical profilometer, and beam deflection.An elevated curing temperature (35 or 45 °C) resulted in a smaller elastic modulus and, despite an accelerated curing reaction and a higher final reactant conversion, only a slight increase, around 0.2 MPa, in the average internal stress. An increased relative humidity (from 35 to 60 %), also resulted in a smaller elastic modulus and less volumetric shrinkage and internal stress. However, at 90 % relative humidity, the internal stress, due to an enhanced final reactant conversion, was higher than observed at 60 % RH.The presence of either BaSO4 or CaCO3 filler in the formulation reduced the final reactant conversion and volumetric shrinkage, but resulted in a higher elastic modulus and internal stress.When the solvent concentration increased from zero to 20 vol%, the final conversion, although extra volumetric shrinkage was introduced by the solvent evaporation, increased from 0.72 to 0.85, while the internal stress decreased from 1.25 to 0.6 MPa.Guidelines for how to optimize coating formulations and curing conditions, to avoid internal stress, are presented.

Evaluation of the stiffness index of carbon fiber reinforced plastics (CFRP) with a hybrid matrix

One of the most important characteristics of structural materials is their stiffness. Ensuring the required stiffness is the key to durability and efficient operation of the structure. Variation in the compositions of polymer composite materials (PCM), the introduction of various additives and modifiers into their structure leads to changes not only in the operational properties of composites, but also in their stiffness. Achieving a positive effect on a number of some properties can lead to the loss of others. This article describes the technology of forming polymer composite materials with a hybrid matrix. The peculiarity of these materials is that the hybrid matrix is formed by two materials, one of which (the main binder) is completely cured after molding, and the second retains its "liquid" state and represents a separate phase in the composite structure. Such PCM have a variable stiffness of material, which makes it necessary to experimentally study the effect of the quantity and location scheme of the "liquid" phase component on this indicator. The technology of the laboratory method for determining the stiffness of PCM samples is described, which consists in measuring the maximum deflection of a flat sample under the action of a statically applied load. The measurement was carried out on carbon fiber reinforced plastic samples with a hybrid matrix formed by an epoxy binder and a silicone elastomer. The influence of the amount and location scheme of silicone elastomer in the composite structure, as well as the scale effect on the maximum deflection was evaluated. The amount of silicone elastomer was taken in a total of 0.25 mL and 0.50 mL in all locations, varying the number of locations and their direction relative to the length of the sample. It was found that the longitudinal location of silicone elastomer in PCM samples leads to the greatest decrease in their rigidity. The amount of silicone elastomer in the location zone does not significantly affect the change in the stiffness of the samples. Increasing the number of layers of reinforcing fabric by 2 times allows to reduce the deflection of the test samples by 7–10 times depending on the applied load. Doubling the width of samples and silicone elastomer locations results in a 2-fold reduction in maximum deflection. With an increase in the thickness of PCM in samples with silicone elastomer, the values of maximum deflection under the action of various statically applied loads are similar to the values of this parameter of carbon fibers of the same thickness without a component of the "liquid" phase.

Infrared thermography of carbon fiber reinforced plastics (CFRP) with a hybrid matrix

The expansion of the fields of application of polymer composite materials (PCM), the emergence of their new compositions and structures is the reason for the development of new and improvement of existing methods for their non-destructive testing. One of the most important tasks in the performance of non-destructive testing of PCM is the development or selection of control modes. The complexity of solving this problem is related to the anisotropy of PCM properties (thermophysical, acoustical, etc.). The article describes the methods and results of infrared thermography of carbon fiber reinforced plastics with a hybrid matrix formed by an epoxy binder and a silicone elastomer. Silicone elastomer is an independent "liquid" phase in the matrix structure (from the standpoint of relaxation properties). The silicone elastomer has high heat resistance, therefore, the choice of modes for performing active infrared thermography of PCM with a hybrid matrix, in which the "liquid" phase is this material, is a rather complex scientific and practical task. The excess temperatures reported to the control object should be in the range of values at which an informative temperature diagnostic signal is observed, but at the same time the destruction of the PCM components does not occur. The values of temperature diagnostic signals from the location zone of the "liquid" phase in the structure of carbon fiber reinforced plastics are presented. It has been established that in order to perform infrared thermography, the temperature of the diagnostic signal from the location zone of the silicone elastomer must be ~3 ± 0.5°C higher than the temperature of the carbon fiber reinforced plastics. The optimal observation time of the temperature diagnostic signal is the period from the end of heating to 0.5 minutes after heating. A model for determining the modes of infrared thermography based on the phonon theory of heat conduction is presented. The temperature corresponding the appearance of a diagnostic signal from the location zone of the "liquid" phase component of the hybrid matrix of the PCM can be considered the Debye temperature of the test material

Interaction researchepoxy binder with basalt by the X method

Basalt, known for its unique properties, is used for the production of yarns, fabrics, nets, and heat-insulating wool. Currently, a research is promoted on applicability of basalt as a dispersed filler for thermo- and rectoplastic materials without processing it into fibers. Therefore, investigation into interaction of epoxy binder with the crushed basalt is promising, which determines the aim of the given study. The objects of the research are the epoxy resin ED-20, polyethylene polyamine PEPA, and dispersed basalt filler. Spectrophotometer "Specord" with the IR-spectrum covering the area of 400 ÷ 4000 cm-1 was used to study the interaction of basalt filler with the epoxy oligomer and hardener. To take the photos of IR spectra of powders, the latter are pressed together with an excess of potassium bromide into tablets several millimeters thick. Special vacuum molds and pressure of several tons per 1 cm2 are used to produce the tablets. The ICS data confirm the interaction of ED-20 not only with PEPA, but also with the dispersed basalt. Amino groups, epoxy rings, CH groups of epoxy and aromatic rings of the binder and hardener undergo a reaction. As the content of the basalt filler in the epoxy increases, the same absorption maxima and bands are observed as in the IR spectra of the composite material with a low content of dispersed basalt. The difference is that the higher the basalt content in the epoxy matrix, the higher the relative intensity of such maxima, which indicates a stronger interaction of the components.

Оценка технологичности материалов, применяемых при производстве и ремонте машин, отличающихся стойкостью к длительному воздействию коррозионных сред

The assessment methodology for manufacturability of fiberglass parts in conditions of small-scale and repair production is given. Materials based on epoxy binders, the curing of which takes place at elevated temperature, were used as objects of the investigation. To compare manufacturability of various molding processes, composites based on dispersed fillers and thermoplastic matrices are also considered. The results of expert assessments of manufacturability are presented, which show that molding processes consisting of similar technological operations in terms of content, differ significantly in cost and material intensity.

Оценка стойкости углепластиков к действию коррозионных сред

The results of structural and mechanical tests of carbon fiber plastics made of carbon tape coated with stainless steel on the basis of an epoxy binder are presented. Carbon fiber specimens were made, using the infusion technology with various curing technologies. The finished specimens were kept in a 7% NaCl solution and the interlayer shear strength and microstructure were evaluated. As a result of the conducted study, it was found that the use of the modified vacuum infusion technology ensures the high quality of the carbon fiber plastics.

INFLUENCE OF THERMOSETTING MODIFIERS ON THE PROPERTIES OF BITUMEN FOR THEIR APPLICATION AT THE ARRANGEMENT OF EPOXY ASPHALT PAVEMENTS ON ROAD BRIDGES

One of the mechanisms of the destruction of asphalt concrete pavement layers on bridges, especially with an orthotropic slab, is a large final deformation, which negatively affects the long-term operational performance of the entire bridge structure. Modification of the asphalt concrete mixture with epoxy components can be very relevant to eliminate the final deformation due to their thermoreactive nature. In this review, epoxy resin and its hardener are considered as the dominant component of the epoxy-asphalt concrete composite system, and based on the results of studies on determining the effect of temperature on the rate of hardening of epoxy resin, on the results of the selection of a binder for the production of epoxy-asphalt concrete mixtures and establishing the viability of an epoxy binder with different contents of epoxy components in bitumen, this article discusses the methods and mechanism of its hardening. The research mentioned in this description is also very useful from a practical point of view, because thanks to the obtained results of determining the viscosity of epoxy-asphalt concrete, depending on the amount of epoxy components in its composition, it is possible to determine the permissible time for its arrangement, taking into account possible features. With the aim of using epoxy-asphalt concrete coatings on road bridges and thanks to the conducted studies, the influence of the introduction of epoxy components as thermosetting modifiers on the properties of bitumen was determined. The research methodology and the obtained results of already conducted research will allow to determine the possibility of using certain components for the preparation of epoxy-asphalt concrete mixtures and their viability. It will make it possible to make an optimal selection of the mixture, taking into account the variation of temperatures and the content of epoxy components. Key words: epoxy asphalt concrete, epoxy resin, coating on bridges, bitumen modification, bitumen properties, viability of modified bitumen.

Modification of epoxy binder with multi walled carbon nanotubes in hybrid fiber systems used for retrofitting of concrete structures: evaluation of strength characteristics

The rapid development in infrastructural facilities necessitates an efficient approach for the repair and retrofitting of concrete structures and, confinement method using fiber reinforced polymer is a promising one. The commonly used carbon and glass fibers for confinement poses environmental and performance issues. The present study addresses these two major aspects by considering natural fibers along with modification of epoxy binder to impart ductile behavior ie., to investigate the effectiveness of multiwalled carbon nanotubes (MWCNT) incorporated synthetic and natural fiber reinforced polymer (FRP) systems as the external confinement. MWCNT is incorporated in 0.5–1.5wt.% in epoxy nano and epoxy multiscale and there is significant enhancement in tensile and fracture properties of the composites up to 1wt.%, beyond which it declined due to agglomeration. Various strength tests were performed with sisal, basalt, carbon and hybrid sisal-basalt FRP systems with different FRP layer thickness on plain concrete cylinders. From the test results it is outlined that external confinement with MWCNT incorporated FRP improved the axial load-carrying capacity, energy absorption and ductility of concrete with respect to that of control specimens. Compared with unconfined specimens, those strengthened with MWCNT modified hybrid FRP wraps containing sisal and basalt fibers recorded increments of 114% and 87% in their load-carrying capacity and energy absorption, due to the intrinsic rigidity of hybrid fibers and epoxy modification. Furthermore, the outcomes indicate that MWCNT incorporated hybrid sisal-basalt FRP confined specimens exhibited superior properties and the low strength of natural FRP confinement compared to artificial FRP can be improved by epoxy modification. The outer jacketing resisted abrupt and catastrophic failure to a great extent.

Processing and characterization of tailorable 3D-printed acrylonitrile butadiene styrene composites with hybrid buckypapers

In this work, a hybrid additive manufacturing process was used to incorporate hybrid buckypapers into an acrylonitrile butadiene styrene matrix. The buckypapers were made onsite during manufacturing from a suspension containing carbon nanotubes, short carbon fibres, and polymer binders. The 3D-printed composites were post-processed by vacuum bagging. The composites reinforced with hybrid buckypapers showed a higher tensile strength by 18% and a tensile modulus by 20% than neat ABS. Further improvement in tensile properties (up to 39%) was observed after the modification of hybrid buckypapers with epoxy or thermoplastic polyurethane binders. The porosity was reduced from 4.8% to 0.5% after the post-treatment of ABS. The microstructure of the hybrid buckypapers and the resulting mechanical properties of the composites depended on the weight fraction (1, 5, or 10 wt%) of binders. The composites without binders were the most porous and experienced a 64% reduction in interlaminar shear strength. The thermoplastic polyurethane had a negligible impact on interlaminar shear strength, while the epoxy binder fully recovered it. The results showed that the mechanical properties and morphology of composites containing hybrid reinforcement can be tailored by selecting the type and weight fraction of the polymer binder system.

Effect of Long-Term Thermal Relaxation of Epoxy Binder on Thermoelasticity of Fiberglass Plastics: Multiscale Modeling and Experiments.

The work is devoted to the prediction and experimental research of the elastic bending modulus of glass-reinforced plastics with an epoxy matrix on anhydride hardener reinforced with different glass fabrics. Experimental studies have been carried out to assess the effect of thermal relaxation of the polymer matrix structure due to long-term exposure to elevated temperatures (above the glass transition temperature of the polymer matrix) on the GRP elastic bending modulus at temperatures ranging from 25 to 180 °C. It has been shown that due to the thermal relaxation of the polymer matrix structure, the GRP modulus increases significantly at temperatures above 110 °C and decreases slightly at lower temperatures. Using a multiscale simulation based on a combination of the finite-element homogenization method in the Material Designer module of the ANSYS software package and three-point bending simulation in the ANSYS APDL module, the elastic modulus of FRP was predicted concerning the temperature, its averaged structural properties, and thermal relaxation of the polymer matrix structure. We have also carried out the prediction of the temperature dependences of the modulus of elasticity of glass-reinforced plastics on different types of glass fabrics in the range from 25 to 200 °C by using the entropic approach and the layered model.

Исследование влияния медного покрытия на свойства углепластиков

The results of experimental studies of the adhesive, elastic and strength characteristics of carbon fiber plastics made on the basis of carbon tapes and fabrics, on the surface of which a copper coating is deposited, are presented. Carbon fiber plastics were manufactured using the vacuum infusion technology with an epoxy binder. It was established that the value of adhesive strength in the carbon fiber-epoxy matrix system, determined by the pull-out method when applying a copper coating to carbon reinforcing materials, increased by 7—25%. The copper coating also has a positive effect on strength of the interlayer shear, the value of which increases by 15—60%. To a less extent, metallization of reinforcing materials affects the magnitude of the elastic modulus of carbon fiber plastic.

Water-Based LiNi0.83Co0.12Mn0.05O2 Electrodes with Excellent Cycling Stability Fabricated Using Unconventional Binders

Water-based processing of positive Li-ion battery electrodes is becoming increasingly important to enable green and sustainable electrode production. Although already widely established for carbon-based anodes, the water-based coating process still poses challenges if applied to cathode materials containing high contents of nickel. Positive electrodes using Ni-rich cathode materials with areal capacities of 2.6 mAh cm−2 were prepared either with Epoxy, a polyisocyanate-based (ICN) binder or polyacrylic acid (PAA). All three binders can cross-link with Na-carboxymethyl cellulose (CMC) used in the formulation. In bi-layer pouch-cells, such cathodes based on Epoxy or ICN binders reach an excellent long-term 1 C charge/discharge capacity retention of 85% and 88% after 1000 cycles, whereas electrodes with PAA only reach 65%. Post-mortem analysis of cells after cycling suggests aging of the cathode electrode as main source of deactivation. According to scanning electron microscopy data, the aqueous processing does not lead to a stronger cracking of the secondary CAM particles and no enhanced dissolution of transition metals was found on the anode side. However, a stronger increase in charge-transfer impedance is observed for the aged water-based cathodes. Thus, the formation of a blocking surface layer appears to be the major reason for performance deterioration with increasing cycle number.

Could a bio-resin and transparent pavement improve the urban environment? An in field thermo-optical investigation and life-cycle assessment

Pavements affect the urban microclimate and the overall quality of the outdoor environment. Cool pavements, in particular, can guarantee lower surface temperature than conventional ones, e.g. asphalt and concrete. These solutions often comprise reflective coatings placed above existing pavements or more complex configurations, i.e. evaporative and heat harvesting solutions. This study investigates in-field the thermo-optical profiles of cool paving systems made with a novel modified epoxy resin binder. Unlike classic binders, the presented binder is transparent and, when combined with the proper aggregate minimizes its contribution to local surface overheating phenomena. The two novel fields presented herein were found to maintain up to 9.2 °C and 6.4 °C lower surface temperature during daytime and up to 8.4 °C and 4.6 °C lower surface temperature during nighttime as compared to the asphalt and concrete fields, respectively. A cradle-to-gate life cycle assessment showed that the novel binders may also decrease pavements’ footprint on human health and ecosystems, while the application of a CO2 off-set model showed their good potentiality to decrease the corresponding emissions. The novel binders, that unlike typical cool paving applications are an integral part of the pavement, are ready to be integrated in real life applications.

Life Cycle Cost Analysis of High Friction Surface Treatment Applications

Life cycle cost analyses for high friction surface treatment (HFST) applications were executed relying on a Microsoft Excel program developed by the researchers. Calcined bauxite (CB), five CB alternatives, and epoxy binder were utilized in the HFST applications. The aggregates’ performances were evaluated through the aggregate image measurement system (AIMS) before and after Micro-Deval polishing. The performance of the HFST applications was evaluated by the dynamic friction tester (DFT) and British pendulum (BP). The major purpose of this program was to present a rational method for converting different input data (project and material specifics) to comparable output data (net present value [NPV]) that facilitated comparison between different alternatives. The project specifics included traffic data, highway classification, and geometric design data. The material specifics data were AIMS results, DFT results, BP results, and materials and shipping costs. Three prediction models were selected to relate the performance test results to skid number (SN). The rehabilitation matrix, proposed by the researchers, was used to make the decision to maintain the HFST. This was conducted by comparing the predicted terminal SN and the recommended terminal SN (controlled by the user). The program output showed that Meramec River Aggregate and Flint HFST applications had the lowest NPVs, followed by Steel Slag HFST application, and then Earthworks HFST application. Nevertheless, Rhyolite HFST application showed the highest NPVs followed by the CB HFST application. The cost of the resin was dominant over the total cost of the HFST application.

Prediction of hydrostatic strength of spheroplastics

In this work, calculations of the hydrostatic strength of a spheroplastic are carried out using the previously described empirical formula. The calculations were based on the physical and mechanical characteristics of the polymer binder and hollow glass microspheres. Measurements of the physical and mechanical characteristics of the polymer binder, hollow glass microspheres and spheroplastics were performed with standard methods: dynamic mechanical analysis (DMA), gas and hydrostatic pycnometers. The results of tensometric tests of Poisson’s ratios of binders were also used. The hydrostatic strength measurements were carried out in a high pressure hydrochamber. Comparison of the calculations and experimental data for a number of spheroplastic compositions based on multicomponent epoxy binders is carried out. The degree of influence of the properties of microspheres and binders on the hydrostatic strength of a spheroplastic is shown. The correlation of the calculated values with experimental knowledge is assessed.

Uji Kekuatan Bending Pipa Komposit Jute-Epoxy pada Perlakuan Rendaman Air Panas

The main purpose of this study was to determine the comparison of the bending strength of composite pipes when treated with hot water. In this study, composite pipes were made using woven sacks and tied with an epoxy matrix which was molded using the VARTM (Vacuum Assisted Resin Transfer Molding) method. Jute fiber laminated composite on epoxy binder is made by laminated 3 layers with fiber direction 450 and has a thickness of 2.55 mm, the jute-epoxy composite pipe will be treated with heat treatment. Then tested on bending loading. The results of this study were the bending stress and strain on the control specimen compared to the heat treated specimen, an increase in the strain of the heat treatment specimen was 0.007 [MPa], this was due to the heat treatment temperature on the specimen which caused a change in the properties of the specimen itself, which was initially a brittle specimen changes to plastic. Meanwhile, the value of bending stress and modulus of elasticity on control specimens and heat treatment specimens. The obtained stress on the control composite pipe is 67.946 [MPa] with a modulus of elasticity of 10.398 [GPa]. While the heat-treated composite pipe has a bending stress of 28.613 [MPa] with an elastic modulus of 2.225 [GPa].

The effect of adding natural materials waste on the mechanical properties and water absorption of epoxy composite using grey relations analysis

Recently, there has been a tendency for scientific studies to deal with natural materials as fillers and reinforcement for polymer composites, which are used in many different applications due to their environmentally friendly properties when compared to synthetic materials. The current study aims to preserve the environment by dealing with natural materials and their influence on the mechanical properties and water absorption property of the polymer composites. In this study, epoxy composites were produced from local natural sourced non-hazardous raw natural materials using grey relational analysis (GRG). The materials used for fabrication include micro-filler of pollen palm 50 μm, seashell 75 μm and epoxy resin. Nine different composites were prepared using pollen palm and seashell as reinforcement material by varying the wt % of the micro-filler. Rule of the mixture was used for formulation and wt % of (0.5, 1 and 1.5) % reinforcement and 99.5, 99 and 98.5 % epoxy (binder) were used for composites. Grey relational analysis was conducted in order to scale the multi-response performance to a single response. The results indicate that optimum performance can be achieved with the addition of 1.5 wt % micro-filler of seashell, which achieved the first rank, while the second rank achieved by 0.5 wt % micro-filler of palm pollen and seashell when compared to other composites. The addition of micro-fillers has improved greatly the mechanical properties of epoxy composites. The loading of micro-fillers has influenced the water absorption property of composites based epoxy in ascending order

Bio-Based Epoxy Binders from Lignin Derivatized with Epoxidized Rapeseed Fatty Acids in Bimodal Coating Systems

In the recent decade, a strong push toward development of more biobased binders for coating applications as part of the transition toward independence from nonrenewable fossil-based raw materials has been seen. Here we present a biobased epoxy lignin/rapeseed fatty acid derivative (eFA-L), which has been applied in coating systems, leading to coatings with >97% biobased content and Y = 130 MPa. To approach the strength of classical epoxy systems, a series of bimodal systems, containing low molecular weight adducts of biobased diglycidyl furan-2,5-dicarboxylate (DGFDC) and fossil-based diglycidylether bisphenol A (DGEBA) were prepared. In these bimodal systems, it was shown that DGEBA contributes to higher mechanical strength compared to DGFDC at equivalent cross-linking density, which was attributed to increased π–π stacking interactions. The biobased bimodal binder system composed of eFA-L and DGFDC (30 wt %) resulted in a coating with a biobased content of 93 wt %, Y = 440 MPa, and Tg > 50 °C. Better mechanical properties (Y = 700 MPa) were achieved by use of DGEBA (30 wt %), but it results in a significant reduction in biobased content to 62 wt %.

Local elastic and limit strength characteristics of epoxy compositions with hollow glass microspheres

A method is proposed for predicting local elastic characteristics and ultimate strength parameters under monoaxial compression of epoxy compositions with hollow glass microspheres. The method takes into account the composition, volume fractions of the components of syntactic foams, and the characteristic size of microspheres (the ratio of the shell thickness to the cavity radius). Model calculations are carried out, taking into account changes in these parameters. Keywords: microsphere, epoxy binder, syntactic foam, syntactic, stress concentration operator, mehanical strength, modeling. alekc_sap@mail.ru

Investigation of the modifier 2-benzofuran-1,3-dione content effect on the heat resistance of epoxy composites

The technological aspects of modification of epoxy oligomer DER – 331 to provide improvement of thermophysical characteristics of composite materials and protective coatings based on them are presented. Cold-cured triethylenetetramine TETA hardener was used to crosslink the epoxy binder (q = 10 parts by weight per 100 parts by weight of DER-331 epoxy resin). Thermogravimetric (TGA) and differential thermal (DTA) analysis was performed to study modified composites under the influence of elevated temperatures. A mathematical calculation of the values of the activation energy of thermal destruction to determine the resistance to destruction of chemical bonds under the influence of temperature factor.