Epoxy Vinyl Ester Research Articles

Compression after low velocity impact tests of marine sandwich composites: Effect of intermediate wooden layers

In the present work, compression after impact (CAI) behavior of sandwich composite materials with intermediate wooden layers was investigated. Sandwich panels were manufactured by using vacuum assisted resin transfer molding (VARTM) method with pinewood and ashwood intermediate layers. 15 and 25mm thick PVC foams with a same density of 80kg/m3 were chosen in conjunction with the face sheets composed of non-crimp biaxial E-glass fabrics and bisphenol-A epoxy vinyl ester resin material system. Impact tests were performed under 30J (low) and 60J (high) energy levels with conical and hemispherical impactors. CAI tests were conducted in accordance with the ASTMC364/C364M-07 standard. Using pinewood and ashwood intermediate layers increased the residual CAI strength and decreased the depth of the impact damage. The intermediate wooden layers have also a potential to reduce the thickness of the composite face sheets and foam core which may increase the proportion of the recyclable wooden materials within the sandwich structure.

Anisotropy and holes in epoxy composite reinforced by carbon/glass and carbon/aramid hybrid fabrics: Experimental and analytical results

Abstract This study is based on research into the effect of anisotropy and the presence of holes on mechanical properties and final fracture characteristics in uniaxial tensile testing of two laminates, one using a carbon/glass fiber hybrid fabric and the other a carbon/aramid fiber hybrid fabric in loading directions at 0°, 90° and ±45°. Both laminates were impregnated with epoxy vinyl ester thermosetting resin (Derakane Momentum™ 411-350). An analytical study assesses stress concentration using the Point Stress Criterion (PSC) and Average Stress Criterion (ASC). The results show the direct influence of anisotropy, holes and residual properties on all the parameters studied. With respect to failure theories, both PSC and ASC showed good agreement when the geometric K value was used.

Enhanced microwave absorption property of Fe3O4/CaCu3−xMgxTi4−ySnyO12(0≤ x, y ≤1)/graphene oxide nanocomposites in epoxy vinyl ester resin

In this study, CaCu3Ti4O12, CaCu2MgTi4O12, CaCu3Ti3.5Sn0.5O12 (CCTO) and Fe3O4 nanoparticles were synthesized and characterized by XRD and SEM. Then, the nanocomposites containing different types and content of CCTO, Fe3O4 and grapheme oxide in epoxy vinyl ester resin were prepared and the microwave absorption property of the prepared nanocomposites was investigated. The type and content of CCTO, content of Fe3O4 and content of graphene oxide were optimized by Taguchi method to obtain the nanocomposite with higher microwave absorption efficiency. The higher absorption efficiency was obtained by the nanocomposite prepared in optimal condition including 3 wt% of CaCu3Ti4O12, 1 wt% of Fe3O4 and 2 wt% of graphene oxide. The reflection loss for prepared nanocomposite was less than −30 dB (absorption ~99, 9%). The great values of the dielectric loss and magnetic loss indicated microwave absorption ability of prepared nanocomposite arises from the effective combination of dielectric–magnetic loss mechanisms.

Effect of Micro Glass Flake on Morphological and Rheological Behaviour of Epoxy Vinyl Ester Composite Coatings

In the present work, attempts were made to investigate the reinforcement and treatment effect of GF on morphological and rheological behaviour of GF/epoxy vinyl ester composites. GF was incorporated into epoxy vinyl ester resin by sonication, and mechanical agitation. Rheological and morphological properties were studied as a function of particle treatment and size distributions. The dispersion morphology, agglomeration degree and homogeneity of additives were analyzed by scanning electron microscopy SEM, and optical microscopy. Effect of mixing method, surface treatment, and particle size distribution on rheological properties of composites were investigated with a modular compact rheometer. The results showed that the mechanical agitation decreases GF aspect ratio more than sonication. SEM fractography shows finer particles improve toughness properties of the composites in comparison with larger ones. GF with larger circular diameter and length is more sensitive to shear than the smaller one. Rheological investigations showed that surface treatment improves the interaction between the polymer matrix and GF. These results indicated that the finer the GF, the better the rheological properties will be displayed.

Mechanical performance of hybrid thermoset composites: Effects of matrix and reinforcement hybridization

Hybrid epoxy/vinyl ester (EP/VE) and epoxy/unsaturated polyester (EP/UP) resins were used as matrices to prepare unidirectional carbon fibre (CF) and carbon/glass fibre (CF/GF) reinforced composites targeting toughness of improvement. Hybrid resins were produced simultaneously (one-pot) and sequentially. (Thermo)mechanical properties of hybrid resins were determined in surface hardness, three-point bending, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC) tests. Hybrid matrix composites with CF and CF/GF hybrid reinforcements were characterized with quasi-static mechanical (three-point bending) tests performed in 0° (longitudinal) and 90° (transverse) directions. In addition, flexural fatigue tests were run on UD composites. Interlaminar properties were deduced from in-plane shear strength (IPSS) test and fractographic inspection in a scanning electron microscope. The EP/VE hybrid resin exhibited improved energy absorption compared to neat constituent resins in contrast to EP/UP. Using hybrid resins as matrix highly improved the toughness and durability of the corresponding composites. Improved energy absorption was attributed to the phase structure of the hybrid resins, which also positively affected the IPSS.

A Composite Fabrication Sensor Based on Electrochemical Doping of Carbon Nanotube Yarns

This work shows evidence of conventional liquid and polymer molecules doping macroscopic yarns made up of carbon nanotubes (CNT), an effect that is exploited to monitor polymer flow and thermoset curing during fabrication of a structural composite by vacuum infusion. The sensing mechanism is based on adsorption of liquid/polymer molecules after infiltration into the porous fibers. These molecules act as dopants that produce large changes in longitudinal fiber resistance, closely related to the low density of carriers near the Fermi level of bulk samples of CNT fibers, reminiscent of their low‐dimensional constituents. A 25% decrease in fiber resistance upon exposure to electron–donor radicals formed during epoxy vinyl ester polymerization is shown as an example. At later stages of curing the matrix undergoes shrinkage and applies a compressive stress to the fibers. The resulting sharp increase in electrical resistance provides a mechanism for detection of the matrix gel point. The kinetics of resistance change during polymer ingress are related to established models for macromolecular adsorption, thus also enabling prediction of polymer flow. This is demonstrated for vacuum infusion of a 150 cm2 glass fiber laminate composite, with the CNT fiber yarns giving accurate prediction of macroscopic resin flow according to Darcy's law.

Structural degradation and mechanical fracture of hybrid fabric reinforced composites

This investigation involves the study of accelerated environmental aging in two polymer composite laminates reinforced by hybrid fabrics based on carbon, Kevlar and glass fibers. Composite laminate configurations are defined as a laminate reinforced with E-glass fiber and Kevlar 49 fiber hybrid fabric (GK) and another laminate reinforced with E-glass fiber and AS4 carbon fiber hybrid fabric (GC). Both laminates were impregnated with epoxy vinyl ester thermosetting resin (Derakane 470-300) consisting of four layers. Morphological studies (photo-oxidation process and structural degradation) of environmental aging were conducted, in addition to comparative studies of the mechanical properties and fracture characteristics under the action of uniaxial tensile and three-point bending tests in specimens in the original and aged conditions. With respect to uniaxial tensile tests for both laminates, good mechanical performance and little final damage (small loss of properties) was caused by the aging effect. However, for the three-point bending tests, for both laminates, the influence of aging was slightly higher for all parameters studied. The low structural deterioration in the laminates is attributed to the high performance with the heat of the matrix (Derakane 470-300) and the characteristics of the hybrid fabric, exhibiting fiber/matrix interface quality. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Glass optical fibre sensors for detection of through thickness moisture diffusion in glass reinforced composites under hostile environments

A combination of evanescent wave optical sensors (EWOSs) and fibre Bragg gratings (FBGs) were embedded in an epoxy vinyl ester and an epoxy vinyl ester based glass reinforced polymer (GRP) composite to measure fluid ingress that would result in degradation under hostile conditions. Samples were subjected to accelerated aging in the form of single sided exposure to simulated sea water at 120°C in a pressurised stainless steel vessel. Low cost EWOSs were prepared from a standard multimode glass optical fibre and compared to commercially available FBGs. Both sensors were able to detect the early stage of moisture diffusion into the GRP matrix. The evanescent sensors showed a reduction in the transmitted signal intensity between 1500 and 1650 nm with an increasing exposure time due to a change in the optical properties of the polymer, whereas a peak shift was observed for the FBGs due to the swelling of the resin with the absorption of water. Additionally, the glass optical fibre sensors were embedded in a configuration that allowed the extent of diffusion through the thickness of the GRPs to be monitored, with the fibres in the closest position to the exposure face showing a greater signal change than those positioned further away.

Tensile Characterizations of Optical Fiber Embedded in Epoxy Glass Composite

Photosensitive single mode optical fibers have been embedded in composite sample in order to be used in optical sensors which monitor the health of civil engineering structure.A simple composite with epoxy vinyl ester matrix reinforced with E-glass unidirectional fibers was implemented using two embedded optical fibers. Interfacial adhesion stress was determined using pull-out test and stress values are correlated to fracture mechanisms based on SEM observations.

Durability of an industrial epoxy vinyl ester resin used for the fabrication of a contemporary art sculpture

In this study we report on an assessment of the conservation condition of a sculpture partially made of synthetic polymers, and on the prediction of its long term durability. Compositional analysis, largely based on IR spectroscopy and Raman spectrometry, identified the epoxy vinyl ester resin used for modelling the lower part of the sculpture as the most critical component. Accelerated degradation tests of the epoxy vinyl ester resin possibly employed by the artist were performed in a photodegradation device and separately in a forced-air circulation oven at 140 °C, to simulate natural degradation. The results obtained by monitoring structural and molecular changes by FTIR and UV-Vis spectroscopy, thermogravimetry (TGA) and differential scanning calorimetry (DSC) allowed us to propose a comprehensive mechanism of oxidation. The validity of the prediction of the durability of the resin was corroborated through a comparison with the results obtained evaluating the actual state of conservation of the artwork. © 2014 Elsevier Ltd. All rights reserved.

Development and mechanical properties of carbon fibre reinforced EP/VE hybrid composite systems

In this study epoxy/vinyl ester (EP/VE) based hybrid thermoset resin was developed and used as a matrix in unidirectional carbon fabric reinforced composite. The mechanical characteristics of the hybrid and the individual resins were revealed by dynamic mechanical analysis (DMA), three-point bending, and hardness tests. The produced composites were investigated by three point bending, impact-, and fatigue tests. The morphological characterization of the materials was carried out by atomic force microscopy (AFM). The revealed morphology affirmed that the mechanical properties of the composites were improved by the using of the hybrid resin. Based on the results enhanced inter-laminar properties of the produced composites were exhibited.

The Influence of the Composition of Copolymers of Chlorophosphorus- and Silicon-Containing Methacrylates with a Vinyl Ester Resin on their Properties

The results of investigating the radical copolymerisation of epoxy vinyl ester styrene resin of grade DION 9300 with chlorophosphorus- and silicon-containing methacrylates and the influence of the composition of the copolymers on their properties are presented. It is shown that the copolymers possess reduced flammability and have heat resistance, hardness, and resistance to thermo-oxidative degradation at the levels of a polymer of unmodified vinyl ester resin, but have inferior water resistance.

Optical Fiber Embedded in Epoxy Glass Unidirectional Fiber Composite System

We aimed to embed silica optical fibers in composites (epoxy vinyl ester matrix reinforced with E-glass unidirectional fibers in mass fraction of 60%) in order to further monitor the robustness of civil engineering structures (such as bridges). A simple system was implemented using two different silica optical fibers (F1—double coating of 172 μm diameter and F2—single coating of 101.8 μm diameter respectively). The optical fibers were dynamically tensile tested and Weibull plots were traced. Interfacial adhesion stress was determined using pull-out test and stress values were correlated to fracture mechanisms based on SEM observations. In the case of the optical fiber (OF) (F1)/resin system and OF (F1)/composite system, poor adhesion was reported that may be correlated to interface fracture at silica core level. Relevant applicable results were determined for OF (F2)/composite system.

A self‐healing biomaterial based on free‐radical polymerization

Self-healing chemistry used for damage repair have not previously been demonstrated for free-radical polymerization pathways. However, this chemistry is important for addition polymers such as poly(methyl methacrylate) used in bone cement and epoxy vinyl ester used in dental resins. Self-healing biomaterials offer the potential for safer and longer lasting implants and restoratives by slowing or arresting crack damage. In the free-radical self-healing system reported here, the three components required for polymerization (free-radical peroxide initiator, tertiary amine activator, and vinyl acrylate monomers) are compartmentalized into two separate microcapsules-one containing the peroxide initiator, and the other containing both monomer and activator. Crack damage ruptures the capsules so that the three components mix and react to form a new polymer that effectively rebonds the crack and restores approximately 75% of the original fracture toughness. Optimal healing is obtained by a systematic evaluation of the effect of monomer, initiator, and activator concentration on healing performance.

Vinyl ester/ glass flake nanocomposites: An overview of chemical and physical properties

The protection of steel against corrosion by nano-glass flake containing coatings has been evaluated in this article. Nano-glass flake was incorporated into epoxy vinyl ester resin by mechanical agitation, homogenizer and sonication process. The dispersion morphology and agglomeration degree of nanoadditives were analyzed by optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The effect of micro and nano-glass flake on anticorrosion performance of epoxy vinyl ester coatings were also compared in a salt spray chamber. The influence of nano-glass flake on the thermal behavior of resins was studied using differential scanning calorimetry and thermogravimetric analysis. The results showed that corrosion resistance of coatings improves as the amounts of nano-glass flake increases to 1.5 phr. Nano-glass-flake-filled specimens display a better corrosion protection than the micro-glass-flake-filled ones.

The fabrication of monolithic capillary column based on poly (bisphenol A epoxy vinyl ester resin-co-ethylene glycol dimethacrylate) and its applications for the separation of small molecules in high performance liquid chromatography

A new polymeric monolith was synthesized in fused-silica capillary by in situ polymerization technique. In the polymerization, bisphenol A epoxy vinyl ester resin (VER) was used as the functional monomer, ethylene glycol dimethacrylate (EDMA) as the crosslinking monomer, 1,4-butanediol, 1-propanol and water as the co-porogens, and azobisisobutyronitrile (AIBN) as the initiator. The conditions of polymerization have been optimized. Morphology of the prepared poly (VER-co-EDMA) monolith was investigated by the scanning electron microscopy (SEM); pore properties were assayed by mercury porosimetry and nitrogen adsorption. The optimized poly (VER-co-EDMA) monolith showed a uniform structure, good permeability and mechanical stability. Then, the column was used as the stationary phase of high performance liquid chromatography (HPLC) to separate the mixture of benzene derivatives. The best column efficiency achieved for phenol was 235790 theoretical plates per meter. Baseline separations of benzene derivatives and halogenated benzene compounds under optimized isocratic mode conditions were achieved with high column efficiency. The column showed good reproducibility: the relative standard deviation (RSD) values based on the retention times (n=3) for run-to-run, column-to-column and batch-to-batch were less than 0.98, 1.68, 5.48%, respectively. Compared with poly (BMA-co-EDMA) monolithic column, the proposed monolith exhibited more efficiency in the separation of small molecules.

Effects of Moulding Condition and Curing Atmosphere on the Flexural Properties of Vinyl Ester

The effects of moulding condition and curing atmosphere on the flexural properties of a neat 33 wt.%-styrene epoxy vinyl ester (VE) were investigated. Specimens were prepared using either open or closed moulds, and thermally cured under either air or nitrogen atmosphere. Four-point bending tests were performed with both the top (“air-side”) and the bottom (“mould-side”) surfaces of the cured specimens in tension. The mean flexural moduli for nitrogen-cured and closed-mould specimens were 3% and 9% higher than for air-cured specimens, respectively. However, the mean flexural strength for open-mould air-cured specimens with their air-sides loaded in tension were 65% lower than the mean flexural strengths of open-mould nitrogen-cured or closed-mould specimens. This likely resulted from partial VE resin curing inhibition due to oxygen diffusion into the free surface region of the open-mould air-cured specimens. This creates gradients in the local stiffness and strength in the near-surface region due to lower crosslink density. This effect may be particularly important for thin specimens. These results underscore the significance of exposure to air during open-mould curing on the cured VE flexural properties. Such assessments are crucial for composite part manufacturing utilizing VEs.

Static mechanical properties of GFRP laminates with fly ash and graphite as filler material

Glass fiber reinforced polymer matrix (GFRP) woven fabric composite material was tested to determine tensile, Flexural and Impact strength. In this paper a comparison study is done for Tensile, Flexural and Impact strength taking two different materials such as (i) woven glass fibre Aralide LY 556epoxy matrix laminates and (ii) woven glass fibre Vinyl Ester epoxy matrix laminates. 1% Graphite and 1% Ash clay are used as filler material as the use of fillers in the matrix, gives rise to many combinations that provide increasing load withstanding capability, reduced coefficient of friction, improved wear resistance and improved thermal properties.

Study on the Resin Curing Time and the Mechanical Properties of the Composites

In order to study the curing characteristics of common resins including bisphenol-A epoxy vinyl ester resin, phenolic epoxy vinyl ester resin and unsaturated polyester resin, the curing time of three resins was tested using cobalt naphthenate as accelerator and methyl ethyl ketone peroxide as curing agent. The results showed that the resin curing time reduces with the experimental temperature rising; in order to control the curing time at about 25 minutes when the experimental temperature is 23°C, the curing agent adding proportion of bisphenol-A epoxy vinyl ester resin, unsaturated polyester resin and phenolic epoxy vinyl ester resin are respective about 0.7%, 0.5% and 1.8%. The composites made by bisphenol-A epoxy vinyl ester resin have excellent tensile strength and composites made by phenolic epoxy vinyl ester resin have best bending strength.

Synthesis, properties and applications of interacting blends of acrylated novalac epoxy resin based poly(ester-amide)s and vinyl ester

Epoxy resin based unsaturated poly(ester-amide) resins (UPEAs) were prepared by the reported method. These UPEAs were then treated with acryloyl chloride to afford acrylated UPEAs resin (i.e. AUPEAs). Interacting blends of equal proportional AUPEAs and vinyl ester epoxy (VE) resin were prepared. APEAs and AUPEAs were characterized by elemental analysis, molecular weight determined by vapor pressure osmometer and by IR spectral study and by thermogravimetry. The curing of interacting blends was monitored on differential scanning calorimeter (DSC). Based on DSC data in situ glass reinforced composites of the resultant blends have been prepared and characterized for mechanical, electrical and chemical properties. Unreinforced blends were characterized by thermogravimetry (TGA).