Epoxy Blends Research Articles

Production and characterization of electrical transformer insulating fluid from blending Castor and Neem seed oils

Castor and neem seed oils were first purified separately through the process of acid degumming, neutralization, bleaching, filtering, washing and drying. The refined castor and neem seed oils was mixed thoroughly at a ratio of 40:60, 50:50 and 60:40 to make up weight of 100g each. The blended ratios were synthesized separately through epoxidation and transesterification reactions to satisfactorily remove glycerol and unsaturation and form an epoxy in the triglycerides of the mixture. The epoxidation process of the triglyceride significantly increased the viscosity whereby making the blended fluids more physically, chemically and thermally balanced. The blended oil esters produced were washed properly with distilled water and dried to purify the esters. The blended epoxy castor-neem oil methyl ester in ratio of 40:60, 50:50 and 60:40 (BEME46, BEME55 and BEME64) were characterized and the following results were obtained: the viscosities of BEME46, BEME55 and BEME64 at a lower temperature of 30°C were 9.30 cSt, 9.45 cSt and 9.48 cSt respectively, while the viscosities at a higher temperature of 70°C were 3.30 cSt, 3.32 cSt and 3.48 cSt respectively, using a glass capillary kinematic viscometer and hot water bath setup. The dielectric strength of BEME46, BEME55 and BEME64 were 30.55 kV, 30.75 kV and 32.02 kV respectively using a megger test set. The acid value or neutralization number of BEME46, BEME55 and BEME64 were 0.1683 mgKOHg-1oil, 0.1405 mgKOHg-1oil and 0.1405 mgKOHg-1oil respectively. The densities were 0.8260 gcm-1, 0.8251 gcm-1 and 0.8219 gcm-1 respectively, while the flash points were 165°C, 168°C and 160°C respectively. BEME46, BEME55 and BEME64 were compared with Transformer Mineral oil obtained from APO Transmission station. It was revealed that the blended oil esters met the transformer standard specifications.

Curing behavior and adhesion properties of epoxy resin blended with phenol-liquefied Cryptomeria japonica

Epoxy resin is one of the most important thermosetting polymers. Most of the commercial epoxy resins are prepared by reacting bisphenol A with epichlorohydrin. However, epoxy resins have the drawback of being expensive. How to reduce manufacturing cost is an important issue. Solvent liquefaction is an effective method to convert biomass from solid to liquid. Phenol-liquefied wood contains a large amount of phenol structure which has the potential to react with the epoxide group of epoxy resin. In this study, wood of Cryptomeria japonica was liquefied in phenol with HCl and H2SO4 as a catalyst and named as LW-C and LW-S, respectively. These phenol-liquefied woods were mixed with epoxy resin to prepare blended resins. The curing behavior, thermal properties and wood bonding performance of blended epoxy resins with different weight mixing ratios were investigated. The results show that the gel time of blended resins can be shortened when compared with the neat epoxy resin, especially for those mixed with LW-S. DSC analysis shows blended epoxy resin prepared by mixing with LW-C has a heat flow variation similar to that of neat epoxy resin but a lower peak temperature with less heat released. Blended epoxy resins mixed with LW-C can be used as a wood adhesive to achieve a dry bonding strength similar to that of neat epoxy resin. These results indicated liquefied wood has the potential to prepare epoxy resin. However, the wet bonding strength is still necessary to further improve.

Study on the demethylation of enzymatic hydrolysis lignin and the properties of lignin–epoxy resin blends

To increase hydroxyl content in lignin, demethylation of enzymatic hydrolysis lignin (DML) was conducted using 1-dodecanethiol as nucleophilic reagent and sodium methoxide as catalyst in this work. Under alkaline conditions, the demethylated lignin–epoxy resin (DML-EP) was synthesized by demethylated lignin reacted with epichlorohydrin (ECH). The optimum conditions for the synthesis of DML-EP were: 80 °C, 2.5 h, molar ratio of ECH and NaOH to phenolic hydroxyl of 7.5 and 1.2, respectively. FTIR spectrum showed the epoxy group appeared in the product. Then, the lignin-based epoxy composites were produced by cast molding method. Tensile strength test reflects that DML-EP-reinforced epoxy composites have an obvious improvement in tensile strength and elongation of about 27 and 34% compared to the pure epoxy resin with 5% content. Scanning electron microscopy images showed the fractured surface of DML-EP/epoxy composites was rough. Rheological analysis showed that the cured DML-EP/E-51 epoxy resin composites had better elasticity and bonding effect. TGA experiment showed the thermal stability of DML-EP/epoxy composites was also improved. Non-isothermal method was used to analyze the curing kinetics of E-51 resin and DML-EP/E-51 composites, and the curing apparent activation energy was calculated using the Kissinger and Ozawa methods.

Bio-based tri-functional epoxy resin (TEIA) blend cured with anhydride (MHHPA) based cross-linker: Thermal, mechanical and morphological characterization

ABSTRACTA novel renewable resource based tri-functional epoxy resin from itaconic acid (TEIA) was blended with petroleum based epoxy resin (DGEBA) and fabricated at different ratios. Then, it was by thermally cured with methylhexahydrophthalic anhydride (MHHPA) in presence of 2-methylimidazole (2-MI) catalyst. The tensile, modulus, strength of virgin epoxy resin (41.97 MPa, 2222 MPa) increased to 47.59 MPa, 2515 MPa, respectively, with the addition of 30% of TEIA. The fracture toughness parameter, critical stress intensity factor (KIC) revealed enhancement of toughness in the TEIA bio-based blends system. The thermomechanical properties of TEIA (tri-functional epoxy resin from itaconic acid) modified petroleum-epoxy networks were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The fracture morphology was also studied by the scanning electron microscopy and atomic force microscopy respectively.

Effect of Silane Modified E-glass Fibre/Iron(III)Oxide Reinforcements on UP Blended Epoxy Resin Hybrid Composite

In this current effort a study was made on UP blended epoxy thermosetting polymer and their properties when amino-silane treated e-glass fibre and iron(III)oxide particles were reinforced. The primary goal of this work is to toughen the brittle epoxy resin by blending low strength unsaturated polyester resin. Blending of low strength polyester reduced the brittleness of epoxy with inferior in some mechanical and thermal properties; hence silane treated e-glass fibre and iron(III)oxide particles was reinforced with UP/epoxy polymer blend to improve thermal and mechanical properties. Particle size of 200 nm and glass fibre of 600 g/m2 was used as reinforcements. Fibres and particles were surface treated by an amino silane (APTMS). Usefulness of particles and fibres addition was unveiled by mechanical, thermal, and dielectric properties. The reduced mechanical properties were increased when e-glass fibre and iron(III)oxide filler was reinforced. Glass transition temperature and degradation stability was less for UP/epoxy systems than pure epoxy whereas addition of filler increased Tg and degradation stability. The dielectric results showed increased dielectric constant and loss for UP blended epoxy composite.

High-Performance Printed Circuit Board Materials Based on Benzoxazine and Epoxy Blend System

Epoxy resin has been used as an industrial printed circuit board (PCB) material based on its excellent mechanical strength and adhesion property to metal. Silica nanoparticle is employed as a component of hybrid matrix material with epoxy resin due to its superior electrical insulating properties. In this study, benzoxazine, which has attracted attention as a new generation of electrically insulating material and displays extraordinary thermal stability, was investigated as a candidate for PCB material. Benzoxazine and epoxy/silica nanoparticle hybrid films were prepared to achieve low dissipation factor and improved mechanical stability. Two types of benzoxazines, monobenzoxazine, and linear polybenzoxazine were investigated; for monobenzoxazine-based film, the blend with epoxy resin was required to improve physical property because monobenzoxazine film showed brittle nature which limited the application as a film with proper mechanical strength. Films with higher content of monobenzoxazine over epoxy resin resulted in lower dissipation factor around 0.005 frequency/10 GHz, however, the mechanical property of the film did not meet the condition as a PCB material. On the contrary, the linear polybenzoxazine-based film demonstrated enhanced mechanical stability but showed limitations in adhesion to the copper layer probably due to the lack of polar functional groups. To overcome the drawbacks, linear polybenzoxazine and epoxy blend systems were prepared to produce films with good adhesion and excellent electrical insulation property with the dissipation factor around 0.006 frequency/10 GHz.

CNT and polyaniline based sensors for the detection of acid penetration in polymer composite

Today, polymer composites are used to store liquid chemicals. Monitoring their structural health is crucial. In this study, conductive nanocomposite-based sensors were designed to monitor acid penetration over time. The sensors were made using blends of epoxy resin and additives, such as polyaniline and carbon nanotube (CNT). It appeared that as the concentration of additives increased, the sensors' response time were shorter. The CNT-based nanocomposites had shown an especially high sensitivity. However, to track the acid penetration over time, polyaniline-based sensors seem more adequate. A simple kinetic model was developed to have a better understanding of sensor behavior.

Toughness augmentation by fibrillation and yielding in nanostructured blends with recycled polyurethane as a modifier

In the present paper, we have carefully investigated the morphology and fracture mechanism of the recycled polyurethane (RPU)/epoxy blend system. The second phase (RPU) added to the epoxy resin has a positive effect on the overall mechanical properties. Interestingly, the recycled polymer has a remarkable effect on the fracture toughness of epoxy resin. The mechanism behind the fracture toughness improvement up on the addition of RPU was found to be very similar to that of the incorporation of hyperbranched polymers in epoxy resin. Brittle to ductile fracture was clear in the case of higher loadings such as 20 and 40 phr of RPU in the epoxy resin. The mechanism behind improvement of fracture toughness was found to fibrillation of the RPU phase which was evidenced by the fracture morphology. In fact the force applied to the epoxy matrix was effectively transferred to the added RPU phase due to its strong interaction with the epoxy phase. This effective transfer of force to the RPU phase protects the epoxy matrix without catastrophic failure and we observed 44% increase in G1C values at an addition of 40 phr RPU. This results in the extensive fibrillation of RPU which causes the generation of new surfaces. Thus the impact energy has been fully utilized by the RPU phase. The mechanism is termed as simultaneous reinforcing and toughening and normally reported as a result of cavitations and yielding. SEM, HRTEM and AFM analyses clearly demonstrated the fibrillated morphology of the fracture surface and the formation of nanostructures. This report is first of its kind in the case of both epoxy modification and the elastomer toughening.

Liquefied banana pseudo stem-based epoxy composites: Incorporation of phenol derivative and its characterization

Abstract A typical method of synthesizing epoxy composites is to incorporate diglycidyl ether of bisphenol-A (DGEBA) into a bio-based epoxy resin. In this strategy, pure liquefied biomass is typically used as feedstock and is blended with DGEBA. Liquefied banana pseudo stem (LBPS), a bio-based active mixture obtained by liquefaction with phenol as the solvent, was directly utilized without depuration or additional DGEBA to develop a composite blend epoxy resin (cb-LBPSER). The blending process based on an incorporation of phenol-based epoxy resin (PER) was investigated by Fourier transform infrared spectroscopy, gel permeation chromatography, and thermogravimetric analysis. The cb-LBPSER presented a lower molecular weight and an improvement of 38.45% for shear strength than the pure LBPS-based epoxy resin (LBPSER). Also, the cured cb-LBPSER adhesive displayed a thermal stability comparable to that of PER. In addition, the curing behaviour, the activation energy, and the glass transition temperature were analyzed by diffrential scanning calorimetry and dynamic mechanical analysis. The blend bio-based epoxy composites exhibited an improved performance, confirming its potential as a suitable alternative to commercial PER.

Morphologies and dielectric properties of epoxy thermosets containing poly(N-vinylcarbazole), fullerene-C60 and their charge transfer complex nanophases

Both poly(ethylene oxide)-block-poly(N-vinylcarbazole) (PEO-b-PVK) diblock copolymer and fullerene-capped poly(ethylene oxide) (PEO-C60) were synthesized in this work. The former was obtained via reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate process whereas the latter via click reaction of azido-capped poly(ethylene oxide) with fullerene-C60. Both of the amphiphiles were incorporated into epoxy to obtain the nanostructured thermosets. It was found that the PVK-C60 charge transfer complexes were formed in the ternary thermosetting blends of epoxy, PEO-b-PVK and PEO-C60. The nanostructured epoxy thermosets containing PVK or/and fullerene displayed the enhanced dielectric constants whereas the dielectric loss remained almost unchanged. Nonetheless, the dielectric constants were significantly decreased while both PEO-b-PVK and PEO-C60 were simultaneously incorporated into the thermosets. The depression in dielectric constant is attributable to the formation of the charge transfer complexes of PVK with fullerene-C60. It was found that the dielectric constants can be modulated with the contents of the PVK-C60 charge transfer complexes.

Preparation and Characterization of DGEBA/EPN Epoxy Blends with Improved Fracture Toughness

The physical and mechanical properties of blends composed of two kinds of epoxy resins of different numbers of functional groups and chemical structure were studied. One of the resins was a bifunctional epoxy resin based on diglycidyl ether of bisphenol A and the other resin was a multifunctional epoxy novolac resin. Attempt was made to establish a correlation between the structure and the final properties of cured epoxy samples. The blend samples containing high fraction of multifunctional epoxy resin showed higher solvent resistance and lower flexural modulus compared with the blends containing high fraction of bifunctional epoxy resin. The epoxy blends showed significantly higher ductility under bending test than the neat epoxy samples. The compressive modulus and strength increased with increasing of multifunctional epoxy in the samples, probably due to enhanced cross-link density and molecular weight. Morphological analysis revealed the presence of inhomogeneous sub-micrometer structures in all samples. The epoxy blends exhibited significantly higher fracture toughness (by 23% at most) compared with the neat samples. The improvement of the fracture toughness was attributed to the stick-slip mechanism for crack growth and activation of shear yielding and plastic deformation around the crack growth trajectories for samples with higher content of bifunctional epoxy resin as evidenced by fractography study.

Significantly enhanced dielectric and energy storage performance of blend polymer-based composites containing inorganic 3D–network

Flexible nanocomposites with high permittivity (εr), low loss and high voltage breakdown strength (Eb) are highly desired in microelectronics and electric power systems etc. In order to obtain high energy storage performance, high values of εr and Eb should be achieved simultaneously. Balance between the εr and Eb has been challenged by their inverse behavior relating to filler content. In this study, by constructing a three dimensional-network of high-εr BaTiO3 (3D BT) ceramic fillers in the polyvinylidene fluoride (PVDF)-epoxy blend polymer matrix, an ultra-high permittivity of 292 and a low loss of less than 0.1 were obtained with 31vol% inorganic fillers. Meanwhile, the energy storage density was enhanced by more than 3 times in comparison with the PVDF-epoxy polymer matrix.

Thermal, mechanical properties and morphology of epoxy resins modified with light pyrolysis natural rubber

AbstractInstead of using traditional functional liquid rubbers in toughening epoxy, light pyrolysis natural rubber (LPNR) obtained from scrap rubber was introduced to improve the toughness of cured epoxy resins. Epoxy blends were prepared by physically mixing the epoxy resins with various concentrations of LPNR. The structure, thermal, mechanical properties and morphology of the epoxy blends were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, impact behavior, and scanning electron microscopy. It was found that the inclusion of 5 phr LPNR reached the maximum value in impact strength of the modified epoxies and the presence of LPNR enables the epoxy resins to fracture in a pattern more akin to ductile materials than in case of the neat epoxy which shows features of brittle rupture. The agglomeration of rubber particles decreased the toughness of epoxy resins modified with more LPNR. Meanwhile, the nearly unchanged glass transition temperature of LPNR epoxy samples illustrated weak interfacial adhesion existed between the rubber phase and epoxy matrix due to low compatibility and feeble combination between them. The thermal stability of modified epoxy resins went down because of the existence of LPNR domains inside the matrix. Overall, the LPNR should be further investigated to improve its compatibility and reinforce its combination with the epoxy resins to become a particularly efficient toughening agent because of its cheaper resource and contribution to environmental protection.

Synthesis and Characterization of Nanoclay‐Reinforced Trifunctional “Bioresin‐Modified” Epoxy Blends Enhanced with Mechanical and Thermal Properties

AbstractEpoxy/TEIA clay nanocomoposite was synthesized from renewable resource based itaconic acid trifunctional bioresin (TEIA) reinforced with Cloisite 93 A nanoclay (C93 A), which was further cured with an anhydride curing agent and 2‐methylimidazole as a catalyst. From the mechanical strength it was observed the tensile strength of virgin epoxy 42.94 MPa enhanced to 70.26 MPa with the incorporation of 2.5 wt% C93 A. Differential scanning calorimetry, thermal analysis, and dynamic mechanical analysis demonstrated that epoxy/30%TEIA with 2.5 wt% organoclay content revealed improvement of the thermal stability and storage modulus. Epoxy/30%TEIA/2.5%C93 A showed raised surface hydrophilicity and increased the wetting energy with increasing clay content. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) studied corroborated that exfoliated formation within the organoclays in the nanocomposites.

Study on the Compatibilizing Effect of Janus Particles on Liquid Isoprene Rubber/Epoxy Resin Composite Materials

Janus hybrid particles (MPS-SiO2@PDVB-DM, JPs) were successively fabricated by grafting dodecyl mercaptan (DM) onto polydivinylbenzene (PDVB) lobe and 3-(trimethoxysilyl)propyl methacrylate (MPS) chains onto SiO2 lobe in the case of SiO2@PDVB Janus particles as the template. Moreover, MPS-SiO2@PDVB-DM Janus particles were used as the compatibilizer of immiscible polymer blends of liquid isoprene rubber (LIR) and epoxy resin (ER). The modified Janus particles were embedded in the interface of LIR and ER, which could improve the compatibility of LIR and ER, mitigating the macrophase separation in the blends. Besides, the compatibilizing effect of MPS-SiO2@PDVB-DM depends not only on the Janus molecular structure but also on the blending process and the curing agent of ER.

Preparation and characterizations of RTV epoxy blends using amide maleic anhydride‐g‐liquid polybutadience as both reactive toughening and curing components

ABSTRACTAmide maleic anhydride‐g‐liquid polybutadience (AMALPB) was synthesized using maleic anhydride‐g‐liquid polybutadience (MALPB) with ethylenediamine (EDA), and its structure was confirmed by FTIR and 1H‐nuclear magnetic resonance spectra, respectively. It was then used as a reactive toughening agent to make blends with diglycidyl end‐capped poly(bisphenol‐A‐co‐epichlorohydrin epoxy cured at room temperature. Their thermal decomposing behaviors did not show much difference because both EDA and AMALPB possessed similar aliphatic groups. All their glass transition temperatures (Tg) increased more than 10 °C than that of the neat epoxy, and with the addition of AMALPB, the blends were greatly strengthened upon heating as show from their storage moduli. When AMALPB was added at 10 wt %, its elongation at break increases to a maximum of 8.8% which was about two times higher than that of the neat epoxy, and its tensile strength also increased. However, the excessive addition of AMALPB resulted in an apparent decline in their tensile strength at content above 20%. The simultaneous improvements in both tensile strength and strain were attributed to the existence of well‐dispersed rubber particles in the continuous matrices performing plastic deformation that resulted from the chemical bonds of interfaces among the rubber particles and matrix, and meanwhile, inducing the deflection of the cracks. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45985.

Development of toughened bio‐based epoxy with epoxidized linseed oil as reactive diluent and cured with bio‐renewable crosslinker

In the current work, renewable resourced toughened epoxy blend has been developed using epoxidized linseed oil (ELO) and bio‐based crosslinker. Epoxidation of linseed oil was confirmed through FTIR and 1H NMR spectra. The ELO bio‐resin was blended at different compositions (10, 20, and 30 phr) with a petroleum‐based epoxy (DGEBA) as reactive diluent to reduce the viscosity for better processibility and cured with cardanol‐derived phenalkamine to overcome the brittleness. The flow behavior of the neat epoxy and modified bio‐epoxy resin blend systems was analyzed by Cross model at low and high shear rates. The tensile and impact behavior studies revealed that the toughened bio‐epoxy blend with 20 to 30 phr of ELO showed moderate stiffness with much higher elongation at break 7% to 13%. Incorporation of higher amount of ELO (20 to 30 phr) increases enthalpy of curing without affecting peak temperature of curing. The thermal degradation behavior of the ELO based blends exhibits similar trend as neat epoxy. The higher intensity or broadened loss tangent curve of bio‐epoxy blends revealed higher damping ability. FE‐SEM analysis showed a rough and rippled surface of bio‐based epoxy blends ensuring effective toughening. Reduced viscosity of resin due to maximum possible incorporation of bio‐resin and use of phenalkamine as curing agent leads to an eco‐friendly toughened epoxy and can be useful for specific coating and structural application.

Wax Confinement with Carbon Nanotubes for Phase Changing Epoxy Blends.

A paraffin wax was shape stabilized with 10 wt % of carbon nanotubes (CNTs) and dispersed in various concentrations in an epoxy resin to develop a novel blend with thermal energy storage capabilities. Thermogravimetric analysis showed that CNTs improve the thermal stability of paraffin, while differential scanning calorimetry showed that the paraffin kept its ability to melt and crystallize, with enthalpy values almost proportional to the paraffin fraction. In contrast, a noticeable loss of enthalpy was observed for epoxy/wax blends without CNTs, which was mainly attributed to the partial exudation of paraffin out of the epoxy matrix during the curing phase. Dynamic mechanical thermal analysis contributed to elucidate the effects of the melting of the paraffin phase on the viscoelastic properties of the epoxy blends. Flexural elastic modulus and strength of the blends decreased with the wax/CNT content according to a rule of mixtures, while flexural strain at break values deviate positively from it. These results show the potentialities of the investigated epoxy blends for the development of multifunctional structural composites.

Effects of Metal Fillers on Properties of Epoxy for Rapid Tooling Inserts

Metal filled epoxy has been recognised as an alternative material used in rapid tooling application such as core and cavity for injection moulding. The addition of fillers into the metal filled epoxy has proven to increase the epoxy’s mechanical performance such as wear, strength, improved machinability and thermal properties. Physical and thermal properties such as density, thermal diffusivity , thermal conductivity and compressive strength were analysed to evaluate the effects of inclusion of metal fillers such as copper and brass particles into the blended epoxy matrix. Brass and copper powders were added separately ranging from 10%, 20% and 30% of its weight into the aluminium filled epoxy mix ratio. Increased density, thermal diffusivity and thermal conductivity values were evident with a linear trend when both filler compositions were increased from 10% to 30%. Brass and copper density values of 2.22 g/cm 3 and 2.08 g/cm 3 respectively were recorded at the highest filler composition. Copper fillers with 30% composition in epoxy matrix exhibited the highest average value of thermal diffusivity of 1.12 mm 2 /s and thermal conductivity of 1.87 W/mK, while inclusion of brass showed no significant improvement on the properties. Compressive strength increased from 76.8 MPa to 93.2 MPa with 20% of brass fillers and 80.8 MPa with 10% of copper fillers composition. The addition of more metal fillers resulted in a decrease in compressive strength due to the presence of porosity. This study validated previous researchers that fillers enhance mechanical, thermal properties and density of aluminium filled epoxy.

Damage recovery after impact in E-glass reinforced poly(ε-caprolactone)/epoxy blends

Damage recovery after low-velocity impact has been assessed in woven E-glass fibre-reinforced polymer composites with an epoxy matrix and a blend of epoxy and 25vol% of poly(ε-caprolactone) (PCL). Impact was carried out at three energy levels (8.5, 17, 34J) and composites with epoxy-PCL blends demonstrated similar energy absorption capacity as compared to pure epoxy composites even though the extent of damage (quantified by C-scans and optical microscopy) was higher. Ultimate compressive residual strength of the modified composites was, for the different impact energy levels, 23–33% lower as compared to unmodified composites. Healing efficiency after a thermal mending cycle at 150°C for 30min has been quantified using three complementary characterization methods; impact damage could be recovered from 20% to 100% depending on the impact energy level. These modified matrix composites are thus able to fully recover low-velocity impact damage at energy levels often met in real structures.