Epoxy Vinyl Ester Research Articles

Enhanced mechanical and thermal properties of epoxy vinyl ester nanocomposites through hybridization with functionalized graphene oxide and nanoglass flakes

This study presents the preparation of epoxy vinyl ester nanocomposites based on hybrid nanofillers, namely functionalized graphene oxide and nanoglass flakes, for outstanding mechanical, thermal, and water resistance properties. Significantly, these hybrid nanocomposites exhibited considerable improvement in tensile strength and modulus, about 39 % and 52 % greater than neat resin, respectively. DSC analysis has shown that Tg increased from 108 °C for the neat resin to 130.9 °C for the FGO/FNGF hybrid nanocomposite, which confirmed an improvement in thermal stability. Water absorption tests have shown a remarkable reduction of moisture intake. Saturation moisture content decreased from 1.35 % for the neat resin to 0.53 % for the hybrid nanocomposite due to the tortuous pathways created by the hybrid fillers. The rheological studies confirmed that better filler dispersion and interfacial bonding are achieved, which is a 34 % increase in the storage modulus with respect to neat resin. SEM studies showed homogeneous distribution of fillers with good filler-matrix adhesion in the case of the hybrid system. The studies thus confirm FGO and FNGF synergies in reinforcement of epoxy vinyl ester nanocomposites for high-performance applications in hostile environments.

Engineering properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy

In this study, the mechanical properties of hybrid polymer composites produced with different unsaturated polyesters and hybrid epoxy resins are investigated. The composites were produced by blending unsaturated polyester resins (i.e., orthophthalic, isophthalic, and terephthalic) and bisphenol-A-based epoxy-vinyl ester resin to produce single, binary and ternary blends. In doing this, a total of 14 different combinations were produced. The results show that the binary and ternary polymer blends tend to improve almost all the tested properties of the polymer composites. Further, the fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) results confirmed that the reason for enahcned properties is due to better crosslinking and longer chains of polymers produced in binary and ternary mixtures. The absence of peaks determining the styrene polymerization character for all mixtures also demonstrates that the polymerization reaction takes place in all mixtures. It is also believed that the binary and ternary resin mixtures have developed higher energy absorption compared to single resin composites. All of the mentioned has been achieved while the gelation temperatures of the hybrid resin mixtures were not changed significantly and they began gelation at the expected temperature values. In addition to the gelation, peak exotherm temperatures, and barcol hardness values demonstrated that all mixtures achieved sufficient curing. The result of this study is significant and point to the great potential of producing high performance polymer composites through the use of binary or ternary resin mixtures.

UAV-Mounted Tank for Processing Agricultural Land with Liquid Agrochemicals

To process agricultural crops, unmanned aerial vehicles carrying tanks with liquid chemicals are used. The paper highlights that containers made of polypropylene and polyethylene exhibit inferior qualities compared to those made of fiberglass, specifically, in terms of strength, thermal stability, resistance to ultraviolet rays, and service life. (Research purpose) To design and manufacture a tank made of composite fiberglass material with a water hammer damper. (Materials and methods) S-glass and epoxy vinyl ester resin were selected for the tank, as they exhibit superior resistance to chemical influences. To construct the tank elements, spray application, impregnation of glass fiber filler in a closed form, and winding were used. (Results and discussion) A comparative analysis was conducted on tank models, assessing their performance with and without a water hammer damper. The effectiveness of the suggested solution has been substantiated through the utilization of KOMPAS-3D software in the KompasFlow application, Within this software, the hydraulic shock is simulated to propagate inside the tank, reflecting off the walls, and gradually diminishing. Load and strength calculations for the fiberglass tank were performed by considering fiberglass parameters using the APM FEM application. (Conclusions) A tank model designed for application of liquid chemical substances in crop spraying from unmanned aerial vehicles has been developed. Innovative methods were employed in the manufacturing of the tank components. Additionally, careful consideration was given to the feasibility of maintenance and reparability. The tank’s volume (experimental sample) measures 0.0158 cubic meters, with a length of 480 millimeters, a width of 216 millimeters, a thickness of 3.6 millimeters, and a weight of approximately 4 kilograms. The design for mounting the composite tank on the unmanned aerial vehicle ensures that the weight of the unmanned aerial vehicle does not impact the tank.

Non-isocyanate epoxy vinyl ester urethane prepolymer based on diglycidyl ether of bisphenol-A

Non-isocyanate epoxy vinyl ester urethane prepolymer based on diglycidyl ether of bisphenol-A

Hygrothermal Effect on GF/VE and GF/UP Composites: Durability Performance and Laboratory Assessment.

In order to investigate the durability of two kinds of fiber-reinforced composite materials, and obtain the degradation mechanism and failure model in a hygrothermal environment, E-glass- fiber-reinforced composite materials, glass fiber-reinforced epoxy vinyl ester and glass fiber-reinforced unsaturated polyester (named GF/VE and GF/UP, respectively) were chosen to suffer rigorous hygrothermal aging. Their mechanical performance was monitored during the aging process to evaluate their durability. The cause of deterioration of the composite was comprehensively analyzed. Based on the analysis results of attenuated total-reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), the change mechanism of chain structure of the resin molecule was proposed. SEM (scanning electron microscopy), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to analyze the microstructure and degradation mechanism of the fiber and the interface between fiber and matrix. The degradation mechanism of the composite system, including the resin, the fiber and the interface, was obtained, and it was found that the deterioration of the matrix resin caused by the hygrothermal environment was the main factor leading to the decline in composites performance.

Effects of Additives on the Mechanical and Fire Resistance Properties of Pultruded Composites.

Under high temperatures, fiber-reinforced polymers are destroyed, releasing heat, smoke, and harmful volatile substances. Therefore, composite structural elements must have sufficient fire resistance to meet the requirements established by building codes and regulations. Fire resistance of composite materials can be improved by using mineral fillers as flame-retardant additives in resin compositions. This article analyzes the effect of fire-retardant additives on mechanical properties and fire behavior of pultruded composite profiles. Five resin mixtures based on vinyl ester epoxy and on brominated vinyl ester epoxy modified with alumina trihydrate and triphenyl phosphate were prepared for pultrusion of strip profiles of 150 mm × 3.5 mm. A series of tests have been conducted to determine mechanical properties (tensile, flexural, compression, and interlaminar shear) and fire behavior (ignitability, flammability, combustibility, toxicity, smoke generation, and flame spread) of composites. It was found that additives impair mechanical properties of materials, as they the take place of reinforcing fibers and reduce the volume fraction of reinforcing fibers. Profiles based on non-brominated vinyl ester epoxy have higher tensile, compressive, and flexural properties than those based on brominated vinyl ester epoxy by 7%, 30%, and 36%, respectively. Profiles based on non-brominated epoxy resin emit less smoke compared to those based on brominated epoxy resin. Brominated epoxy-based profiles have a flue gas temperature which is seven times lower compared to those based on the non-brominated epoxy. Mineral fillers retard the spread of flame over the composite material surface by as much as 4 times and reduce smoke generation by 30%.

Coordination Compound (2,3,5-Triphenyltetrazolium)2[CuBr4] as Catalyst for the Curing Process of Epoxy Vinyl Ester Binders.

This article presents a study on the synthesis and catalytic properties of copper complex (TPhTz)2[CuBr4] (here TPhTz is 2,3,5-triphenyltetrazolium). The obtained complex was characterized by various spectroscopic methods. The catalytic properties of the complex were evaluated in the curing of an epoxy vinyl ester system and their effectiveness was compared with that of cobalt octoate (its synonyms are known as Co(Oct)2, cobalt(II) 2-ethylhexanoate, cobalt isocaprylate, etc.). The catalyst was added at an amount of 2 w.%. The results showed that a 8 w.% solution of the complex provides catalytic properties with an activation energy of 54.7 kJ/mol, which is 25.2 kJ/mol higher than a standard curing system with Co(Oct)2. Thus, the solution of (TPhTz)2[CuBr4] in THF/DMSO accelerates the initiator decay process at room temperature, but for a longer time. The authors suggest that the curing mechanism may be accelerated by the appearance of (TPhTz)2[CuIBr3] and free bromine in the system. A strength test of fiberglass-reinforced plastic revealed that the addition of this complex did not lead to a decrease in flexural strength and hardness. Thus, use of the complex allowed for the production of polymer composite products using vacuum-assisted resin transfer molding where an extended injection time was needed.

Long-term moisture diffusion in vinylester resin and CFRP rebars: A 20-year case study

Moisture absorption in polymer composites is a slow process that can take several decades, so it is often modelled without experimental verification. This unique study reports the moisture diffusion in epoxy vinylester (VE) resin and carbon fibre reinforced pultruded (CFRP) rebars over a period of 20 years at ambient temperature. Non-Fickian diffusion in VE is modelled by the unified two-phase model, which combines the bound water or hindered diffusion and the polymer relaxation concepts. Calculations based on the short-term projection with an unknown true saturation moisture content result in highly underestimated predictions. The true secondary equilibrium is 30–60% higher than the Fickian "pseudo-equilibrium". Moisture absorption of CFRP rebars at 98% RH was studied on short and long samples to identify the axial and radial diffusivities. The concept of apparent diffusivity, combining edge and anisotropy effects, is extended to the case of cylindrical rebars. Rebars absorb up to 0.55% of moisture following the Fickian behaviour, and the predictions are consistent with the calculations using the microstructural considerations. Calculations based on short-term projections result in highly overestimated axial diffusivity and the ratio of diffusion anisotropy. Long-term ageing of VE resulted in up to a 40% reduction in tensile strength and a 10 °C reduction in glass transition temperature. The interlaminar shear strength of CFRP rebars decreased by 30%, and its partial retention after moisture desorption indicated interphase degradation. The results will contribute to an understanding of water diffusion and environmental ageing of VE-based composites, bridging the gap between real-life degradation performance and accelerated durability predictions.

Vanillin and organosilicon functionalized graphene oxide modified ester resin composite coatings with excellent anti-corrosion properties

Epoxy vinyl ester resin is widely used in the field of corrosion protection because of its excellent corrosion resistance and mechanical properties. However, due to the ease of hydrolysis of the ester group in the ester resin, the barrier ability of the coating is reduced, which will accelerate metal corrosion. The existing literature shows that the use of nano-sheet materials such as graphene oxide (GO) can effectively enhance the barrier properties of the coating. In order to solve the poor compatibility and electrical corrosion phenomenon of GO, in this work, renewable vanillin and silicone with excellent anti-corrosive properties were grafted to GO (APGO) by insertion reaction and D-A reaction. Subsequently, a series of new APGO-based epoxy vinyl ester resin composites with excellent mechanical properties and anti-corrosion properties were prepared by thermal crosslinking polymerization. The results showed that when the additive amount of APGO was 0.1 wt%, the comprehensive performance of the composite was the best: the conductivity (1.9 × 10−13–5.6 × 10−13 S/cm) of the composite was far lower than the critical electrical insulation value (10−9 S/cm), the breaking strength was improved by 38.0 %, the contact angle was increased by 65.7 %, and its anti-corrosion efficiency was up to 99.03 %. After 70 days of immersion in 3.5 wt% salt water, the impedance modulus of the composite at low frequency (Zf = 0.01 Hz) remained 2.23 × 1010 Ω cm2, which was 2 orders of magnitude higher than that of pure epoxy vinyl ester resin (2.43 × 108 Ω cm2). The above results were not only related to the maze effect formed by APGO, but also related to the increased crosslinking density of the system. This work provided a novel strategy for preparing GO-based composites with excellent comprehensive properties.

4D Printing Of Shape Memory Epoxy For Adaptive Dynamic Components

AbstractProgrammed 4D printing shape‐memory polymers (SMPs) have been endorsed as an emerging paradigm for developing adaptive dynamic components with sophisticated architectures and biomimetic adaptation capacities. However, the species of SMPs systems are still rare while most of them are produced from expensive monomers which have restricted their mass production. Moreover, most SMPs show poor elongation at break and strain which cannot support a higher degree of bending during shape memory deformation. Herein, a kind of new epoxy vinyl ester resin ink is developed and improves the 4D printing process of shape memory epoxy‐based polymer. By adjusting the printing conditions to match the ink property, a series of precisely designed printing structures are successfully produced. The printed SMP system shows a favorable strain rate under heat‐treated conditions above its glass transition temperature (Tg) which leads to fine shape memory performance. Furthermore, the printed components obtained through micro to macro multi‐scale 4D printing structure design confirm its application potential as dynamic adaptive devices in aerospace and safety engineering.

On the electron beam-induced degradation of vinyl ester thermosets

We have demonstrated that electron beam radiolysis induces scissions of the C-O-C bonds along the backbone of the chains of unsaturated polyester thermosets of different compositions based on dicyclopentadiene, isophthalic acid, epoxy vinyl ester, and terephthalic acid. The radiolysis is imminent irrespective of the degree of crosslinking in the thermosets both in neat resins and in the presence of solvents. Electron Paramagnetic Resonance (EPR) results show the formation of the alkoxyl radicals and C-centered radicals as the primary intermediate products of the C-O-C scissions. While the alkoxyl radicals of these resins exhibit very good stability even six months after the irradiation, the C-centered radicals decay very rapidly via their reactions with oxygen that is available either as adsorbed in the resins, dissolved in solvents or from the environment. The radiolytically produced •OH radicals in the unsaturated-ester aqueous solutions play a major role in inducing scissions on the backbone of the polymer chains. The solvated electrons (es) from organic solvents, such as dimethyl sulfoxide and isopropyl alcohol, also induce direct scission of the C-O-C bonds, giving rise to the formation of alkoxyl radicals and C-centered radicals. However, a considerable fraction of es is scavenged by the dissolved O2 to produce O2−. Despite the radiation-induced scissions, irradiation of the resins at a dose level of 1000 kGy results in an increase of the glass transition temperature, Tg. This is due to the simultaneous radiation-induced polymerization of the vinyl monomers, toluene, and styrene that are present in the resins. The increase in Tg is observed in all the resins except for the terephthalic polyester resin in aqueous solution, in which the absence of these monomers results in Tg decreasing sharply with irradiation. This work demonstrates that ionizing radiation triggers continuous free radical-chain reactions that lead to the formation of recyclable oligomers.

Pultruded carbon fibre reinforced polymer strips produced with a novel bio-based thermoset polyester for structural strengthening

This paper presents the development and industrial manufacturing of a pultruded high-performance carbon fibre (CF) reinforced polymer (CFRP) composite strip using a bio-based unsaturated polyester (UP) resin containing more than 50% of its weight derived from renewable raw materials. The bio-based CF/UP strengthening strip, comprising unidirectional CF strands, was successfully produced and its mechanical and thermomechanical behaviours were assessed, and compared to an equivalent carbon fibre reinforced epoxy-vinyl ester (CF/VE) strip produced with conventional petroleum-based high-performance epoxy-vinyl ester resin and the same fibre architecture. The bio-based CF/UP composite strip presented 2095 MPa, 167 GPa, and 1.4% of tensile strength, modulus of elasticity, and strain at failure, respectively. These figures met or exceeded the mechanical properties of its equivalent conventional CF/VE counterpart tested under the same conditions. Furthermore, the bio-based CF/UP composite strip presented a glass transition temperature of 78 °C (defined from the onset of the storage modulus decay), enabling a maximum service temperature of ∼60 °C, which will not likely be exceeded in most climates, highlighting its potential for structural strengthening applications, and offering a key advantage in terms of sustainability.

Affinity of K+to organic matter promotes reactions: degradation of super stable phenolic epoxy vinyl ester resin to value-added chemicals

An efficient catalytic system was developed to cleave the ester bond of highly stable waste thermoset phenolic epoxy vinyl ester resin and recover value-added chemicals.

An experimental study on the manufacturing of engineered defects in composite plates

Composite materials are finding their way to various applications where their safe usage is of concern. In this regard, accurate inspection techniques must be developed and verified. Composite samples with predefined defects are needed to objectively and accurately assess various damage detection techniques. This study presents a methodology for manufacturing composite plates with engineered defects. The three most common damages in composite parts - delamination, fiber breakage, and matrix crack - are investigated here. This approach can be used by researchers working on damage detection techniques to fabricate composite samples and control the type, size, and location of the embedded defects. Manufacturing and verifying such samples with engineered defects are indispensable to all damage detection studies on composite materials. The samples in this study were 25.4 mm thick, 305×305 mm square plates manufactured via the vacuum infusion method. Stitched triaxial fiberglass fabric and epoxy vinyl ester resin were used as the reinforcement and matrix. The sizes, shapes, and locations of the defects were predetermined and kept constant in all the manufactured samples with high consistency. X-ray tomography was used to verify the characteristics of the defects in the composite plates. The X-ray images showed that defects occurred in their predefined locations, shapes, and sizes with high accuracy.

Mechanical Characteristics Evaluation of a Single Ply and Multi-Ply Carbon Fiber-Reinforced Plastic Subjected to Tensile and Bending Loads.

Carbon fiber-reinforced composites represent a broadly utilized class of materials in aeronautical applications, due to their high-performance capability. The studied CFRP is manufactured from a 3K carbon biaxial fabric 0°/90° with high tensile resistance, reinforced with high-performance thermoset molding epoxy vinyl ester resin. The macroscale experimental characterization has constituted the subject of various studies, with the scope of assessing overall structural performance. This study, on the other hand, aims at evaluating the mesoscopic mechanical behavior of a single-ply CFRP, by utilizing tensile test specimens with an average experimental study area of only 3 cm2. The single-ply tensile testing was accomplished using a small scale custom-made uniaxial testing device, powered by a stepper motor, with measurements recorded by two 5-megapixel cameras of the DIC Q400 system, mounted on a Leica M125 digital stereo microscope. The single-ply testing results illustrated the orthotropic nature of the CFRP and turned out to be in close correlation with the multi-ply CFRP tensile and bending tests, resulting in a comprehensive material characterization. The results obtained for the multi-ply tensile and flexural characteristics are adequate in terms of CFRP expectations, having a satisfactory precision. The results have been evaluated using a broad experimental approach, consisting of the Dantec Q400 standard digital image correlation system, facilitating the determination of Poisson’s ratio, correlated with the measurements obtained from the INSTRON 8801 servo hydraulic testing system’s load cell, for a segment of the tensile and flexural characteristics determination. Finite element analyses were realized to reproduce the tensile and flexural test conditions, based on the experimentally determined stress–strain evolution of the material. The FEA results match very well with the experimental results, and thus will constitute the basis for further FEA analyses of aeronautic structures.

Possible selective physisorption of lower molecular mass of epoxy-vinyl ester chains on the montmorillonite nanoplatelets: A rheological approach

Na+-montmorillonite nanoplatelets were surface functionalized by triethoxyvinylsilane through sol-gel reactions. The functionalized, and pristine nanoplatelets were then impregnated by Octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, a primary phenolic antioxidant, to be used in an epoxy vinyl ester resin. The FTIR, Raman and, TGA results confirm that the functionalization reactions, and the antioxidant impregnation process have been successfully carried out. FE-SEM micrographs demonstrate that particle morphology significantly changed as a result of the processes. In the next step, three different concentrations of the obtained nanofillers were added to an epoxy vinyl ester resin, and the attained colloids underwent rheological assessment. Both steady-shear, and dynamic complex viscosity diagrams showed significantly increased values, by two orders of magnitude, for untreated Na+-montmorillonite compared to the other nanofillers, i.e. vinyl-functionalized, and antioxidant-loaded ones. It was then demonstrated that such an increase is most certainly attributed to a proposed theory as possible selective physisorption of lower molecular mass of epoxy vinyl ester chains on the untreated montmorillonite nanoplatelets.

COMPOSITES FOR CHEMICAL INDUSTRIES

The issue of using composites based on bis-phenolic and epoxy vinyl ester resins in the practice of anti-corrosion protection of technological equipment, in particular, chemical production equipment, is considered. Composites can be used both as coatings and as structural materials in the manufacture of individual parts of equipment, containers, etc. Composites based on these resins can increase the service life of equipment several times. These materials have a wide temperature range of application; can be operated in aggressive environments (acids, alkalis, oxidizing environments); have high adhesion to metal and concrete; strength comparable to the strength of metals; resistance to shock and dynamic loads and the impact of a liquid stream containing a solid phase.

Assessing the mechanical behavior of glass and basalt reinforced vinyl ester composite under artificial seawater environment

Glass and basalt fiber reinforced vinyl ester epoxy (GFRP and BFRP) composites offer considerable potential for underwater and deep sea applications. In spite of their increasing usage in various sectors, there are still questions concerning their long term reliability in marine environment. In this article, the response of GFRP and BFRP to seawater ageing and their subsequent mechanical properties were evaluated. The composites were fabricated by vacuum assisted resin injection technique and seawater aged at 30 0C for 18, 28, 38, 258 and 305 days. By using scanning electron microscope (SEM), the failure of dry and seawater aged specimen after mechanical testing showed fiber breaking, debonding and sporadic fracturing along the laminate. This was due to higher moisture concentration in these areas during ageing. The results also revealed an overall steady decrease in tensile, flexural and impact strengths of seawater aged laminates with increasing ageing duration. Overall, the seawater ageing property of BFRP composites is almost identical to that of GFRP. The use of different nano-materials could also be explored in future works to address some drawbacks in the fiber–matrix interface durability after seawater ageing.

Research on preparation of nano-Sb2O3@Br-VERs core-shell composite particles

Nanoparticles with core-shell structure provide a new potential technology to improve the efficiency of flame retardants. Using nanometer antimony trioxide particles (nano-Sb2O3) as matrix material and brominated bisphenol-A epoxy vinyl ester resin (Br-VERs) diluted by toluene (PhMe) or styrene (ST) as the coating material, PhMe-nano-Sb2O3@Br-VERs and ST-nano-Sb2O3@Br-VERs core-shell composite particles were prepared by electromagnetic stirring method. The results show that Br-VERs can successfully coat on the surface of nano-Sb2O3, thus forming core-shell composite particles with crystalline nano-Sb2O3 as the core and amorphous Br-VERs as the shell. The thickness of Br-VERs shell of PhMe-nano-Sb2O3@Br-VERs composite particles is between 9.5 nm and 15.5 nm, and the shell’s mass fraction is 20.8% in the composite particles. The thickness of Br-VERs shell of ST-nano-Sb2O3@Br-VERs composite particles is between 5.5 and 9.5 nm, and the shell’s mass fraction is 3.8%. The mass of Br-VERs shell of PhMe-nano-Sb2O3@Br-VERs composite particles is 5.47 times that of ST-nano-Sb2O3@Br-VERs composite particles, which indicates PhMe used as the diluent for Br-VERs has a better effect than that of ST used as the diluent.

CFRP Laminates with Recycled Carbon Fiber: Resin Infusion and Mechanical Characterisation

The possibility to produce new components using reclaimed non-woven carbon fabric has been investigated. Being composite waste production increased, different strategies and technologies for recycling are developing to face criticalities and economic aspects related to their disposal. In this scenario, CFRP laminates with recycled carbon fiber and epoxy vinyl ester resin have been fabricated by Resin Infusion under Flexible Tooling (RIFT) and mechanical characterization has been performed to investigate their behavior under tensile, flexural and macro-indentation loads.