Narrow Results

The interlaminar peel strength of Al/AFRP (Aluminum alloy/Aramid Fiber Reinforced Plastic) hybrid composite is affected by the adhesive strength between the Al alloy layer and the aramid fiber layer. The study of the tensile strength and the T-peel strength of the Al/AFRP should be accomplished first. Therefore, this study focused on the effect of the resin mixture ratio as the Al/AFRP on the tensile strength and T-peel strength. In conclusions, the resin mixture ratio by equivalence ratio of 〈epoxy resin : curing agent〉 equal to 〈1:1〉 of Al/AFRP-I and the resin mixture ratio by equivalence ratio of 〈epoxy resin : curing agent : accelerator〉 equal to 〈1:1:0.2〉 of Al/AFRP-II showed the highest ultimate tensile strength. After the T-peel test, it is found that the T-peel strength of Al/AFRP-II is approximately 1.5 times higher than that of Al/AFRP-I. Reviewing the characteristics of the tensile and T-peel strengths, the resin mixture ratio 〈1:1:0.2〉 of Al/AFRP-II showed the highest tensile strength and T-peel strength.

In this paper, a new nano-adhesive which has been improved the conventional epoxy resin that is widely used in the automobile industries was introduced. Multi-walled carbon nano-tubes (MWCNTs) (1%-3% by weight) were mixed into epoxy resin using a mixer. The bubbles generated during the mixing processes were removed using a high vacuum. In order to optimize the quality and performance for actual application, the mechanical properties of the joints taking into account the geometrical parameters of bonded layer were basically assessed. From the results, both the static tensile strength and fatigue strength increased dramatically at a carbon nano-tube weight percentage of 2% compared to other values. The surface treatment condition of the plates also affected the tensile strength of the nano-adhesive bonded joints.

Composites are vulnerable to the impact damage by the collision as to the thickness direction, because composites are being manufactured by laminating the fiber. The understanding about the retained strength after the impact damage of the material is essential in order to secure the reliability of the structure design using the composites. In this paper, we have tried to evaluate the motion of the material according to the kinetic energy and potential energy and the retained strength after impact damage by testing the free fall test of the basalt fiber reinforced composite in the limelight as the environment friendly characteristic.

We study experimentally the influence of mass fraction of L-20 hardener cold cure on mechanical properties of epoxy diane resin ED-20. We measure the hardness, tensile strength, bending strength and impact strength of resin at different values of the hardener mass fraction. It is found that the ratio hardener mass fraction of 1:0.9 leads to the highest values of the hardness, tensile strength, compressive strength and bending strength. The impact viscosity is maximum at the ratio hardener mass fraction of 1:0.8. The optimal ratio of a non-toxic safe hardener to the resin is derived based on obtained mechanical characteristics.

In power system, the post-insulator is a critical apparatus which carries the conductor and also provides isolation between the conductors as well as ground. Besides, it offers mechanical support. However, extreme weather and pollution cause post-insulator flashover, which results in interruption of power supply and revenue loss. Therefore, post-insulator’s pollution flashover study is necessary. The pollution flashover voltage (FOV) is directly related to dominating metrological circumstance and how this pollution severity on the surface of insulator. Mostly, anti-pollution flashover coating is deliberated to be one of the most effective means to prevent and reduce pollution flashover. This paper investigates and compares the application of Epoxy Resin and Room Temperature Vulcanize (RTV) Silicone Rubber for enhancing the performance of ceramic outdoor (near coastal thermal plant area) insulator to defeat the effect of environmental pollution. At first, a real-time pollution performance has been carried out in controlled laboratory setup. It shows that the withstand ability of post-insulator has been 25% with Silicone Rubber coating. Subsequently, Artificial Neural Network (ANN) has been used to predict the FOV of post-insulator under wet and dry condition. It shows that critical FOV has enriched with anti-reflection coating rate. After that, post-insulator has been modeled by COMSOL multiphysics software, which is used for estimating field distribution on post-insulator. From the modeling, we found that anti-reflection coated post-insulator surface has low electrical stress than that of others.

This study investigates the mechanical properties of Luffa cylindrica and snake grass fiber composites prepared with different combinations of fiber and resin. Fibers are produced from natural sources having good mechanical properties and eco-friendly that can be used in various engineering applications such as automobile, aerospace and automotive industries. The Luffa cylindrica and snake grass fibers will be treated for 3h with alkali (NaOH) chemical treatment. The treated fibers are then developed as Laminate composites using compression molding technique. The composites have been made in five different compositions by varying the weight percentage (wt.%) of the chemically treated Luffa cylindrica and snake grass fibers (combination of maximum 30wt.%) mixed with epoxy resin and hardener (maximum of constant 70wt.%). Bonding between the fiber and matrix plays a vital role in influencing the mechanical characteristics of composites. The five samples have been prepared from the five different compositions and undergone various studies to find its mechanical properties such as ultimate tensile test (UTS), impact test, flexural test and water absorption test. It is found that the UTS and flexural strength have been considerably enhanced by sample 2 and impact strength has been notably increased by sample 3. The microstructure of tensile-tested specimen is observed by using the Scanning Electron Microscopy (SEM). It is reported that the better bonding between the fibers and matrix has been observed by SEM microstructural analysis.

Recently, composites have attracted many researchers, which have advanced favored properties compared to metallic materials, such as high strength with lightweight as well as corrosion and erosion resistance and others. However, these resources are exposed to yield during the working life. For these new products and their employing in different applications, and for the mentioned importance, this study has investigated the mechanical characteristics of these structures to avoid potential failure. An investigation of Arcan (shear $V$-notch test) procedure has been conducted for epoxy resin which is used for reimpregnations with Eglass and compared with lightweight metal of Aluminum as a benchmark to show the shear behavior for the composite one under shear load experimentally and numerically. The butterfly-shaped sample was modeled and tested accordingly with Arcan (shear $V$-notch test) numerically in order to produce pure shear force by tensile subjection condition using ANSYS software. The test verified that a state of pure shear was present during the testing on each ± 45^∘ inclined from the axis of subjection although the changes recorded as G magnitude of shear modulus between Aluminum and the thermoplastic of Epoxy resin is nearby 94%, which may be because of the effect of material nature (i.e. mechanical properties) for the selected materials. The mentioned novel constituent shear behaviors have been investigated and compared expediently. These novel constituents can be adopted in different applications of shear loads.

The mechanism of phase inversion emulsification process (PIE) was studied for waterborne dispersion of highly viscous epoxy resin using non-ionic polymeric surfactants. Drop deformation and breakup, rheological properties, conductivity, and particle size measurements reveal the micro-structural transition amid emulsification. It is revealed that strong flow causes water drop to burst with the formation of droplets and huge interface. Phase inversion corresponds to an abrupt rheological transition from a type of viscous melt with weak elasticity to a highly elastic type of aqueous gel. This implies that the phase inversion equivalent to a curvature inversion. Based on this, a geometric model is postulated to correlate process variables to the particle size. The coverage and conformation of the surfactant plays key role for the particle size of the final emulsion. The interactions of thermodynamic and hydrodynamic effects are also discussed. It is concluded that the thermodynamics control the PIE while the hydrodynamics drives the creation of interface and involves every step of PIE.

Due to its mechanical properties and ease of use, vinyl ester resin is enjoying increasing consideration. This resin normally is produced by reaction between epoxy resin and unsaturated carboxylic acid. In the present study, bis-phenol A based epoxy resin and methacrylic acid was used to produce vinyl ester resin. The reaction was conducted under both stoichiometric and non-stoichiometric conditions in the presence of triphenylphosphine as catalyst. The stoichiometric and non-stoichiometric experiments were conducted at 95, 100, 105 and 110°C and at 90 and 95°C respectively. The first order rate equation and mechanism based rate equation were examined. Parameters are evaluated by least square method. A comparison of mechanism based rate equation and experimental data show an excellent agreement. Finally, Arrhenius equation and activation energy were presented.

In this review, our recent work in phase inversion emulsification (PIE) for polymer (especially epoxy resin) waterborne dispersions is summarized. Based on experimental results about PIE process, the physical model is proposed which can guide the synthesis of the waterborne dispersions such as polymer/nanoparticle composite dispersion. In the presence of a latent curing catalyst, PIE can give a crosslinkable epoxy resin waterborne dispersion. The dispersions can form cured transparent coatings with some unique properties such as UV shielding. They are promising in functional coatings, waterborne resin matrices for composites, and sizing for high performance fibers.

Five secondary amine terminated poly(ester-amine)s (defined as PEA) with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate (PDDA) and 1,1,1-trimethylolpropane triacrylate (TMPTA) at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ¹H-NMR spectra indicated that all acrylate groups were consumed in the reaction, based on which the structural parameters were calculated from the ¹H-NMR spectra. With decreasing PDDA/TMPTA ratio, the content of secondary amine, degree of branching, molecular weight, T_g and T_d increased accordingly. These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition. The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branching structures. Due to the flexibility of PEA molecules, all the films possessed excellent mechanical performance.

Caged bicyclic phosphate (CBP) and its dimelamine salt (PDS) were synthesized and added to epoxy resins to obtain the flame retarded epoxy resin composites. The flammability of the composites was characterized by the limiting oxygen index (LOI) and cone calorimeter tests. The LOI values of flame retarded composites increase consistently with the increase of flame retardant amounts, and they are almost the same when the loading of CBP is the same as that of PDS, although the phosphorus content of PDS is much lower than that of CBP. The total heat release increases in the order of CBP30/ER < PDS30/ER < PDS15/ER < CBP15/ER, whereas that of specific extinction area is CBP15/ER > CBP30/ER > PDS30/ER ≌ PDS15/ER. PDS exhibits more effective inhibition of oxidation of combustible gases. In the tests of thermogravimetric analyses (TG) and Fourier transform infrared spectroscopy (FT-IR), it is found that the degradation of the composites is influenced greatly by the addition of flame retardants. By scanning electron microscopy (SEM), a thick and tight char-layer is observed for PDS30/ER, resulting from the interaction of nitrogen species with phosphorus species. Therefore, the combination of CBP with melamine in the flame retarded system can improve the flame retardancy greatly.

Exploration and characterization of grafting productions by experimental methods are often cumbersome or sometimes impossible. Therefore, quantum chemistry calculations were performed to characterize the graft sites of epoxy resin. According to the Gibbs free energy criterion of the second law of thermodynamic, the reported graft sites were confirmed, and more important, some unreported graft sites were found. In addition, method of increasing the number of graft sites was studied in this article.

A two-step method for the preparation of hybrid materials consisting of multi-walled carbon nanotubes (MWCNTs) attached to graphene nanoplatelets (GNPs) was proposed. Firstly, poly (acryloyl chloride) was grafted in situ onto the surface of MWCNTs. Secondly, the obtained MWCNTs (MWCNTs-PACl) were reacted with acid-treated GNPs to form a nanotube–polymer–graphene hybrid. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA) were used to investigate the forming of the hybrid materials. FTIR results showed that MWCNTs/PACl and GNPs were successfully bridged by chemical bonds like O–C = O and C–O–C. Raman spectroscopy furthermore revealed that acryloyl chloride can be used to connect the MWCNTs and GNPs due to the defects of MWCNTs, and consequently the defects of the hybrid materials were limited. Meanwhile, TEM observation demonstrated the nanostructure clearly in which the MWCNTs with a polymer layer were attached successfully on the surface of GNPs. And TGA curves reflected that the content of MWCNTs and GNPs was about 46.5% in the hybrid materials. In addition, the tensile tests results showed that MWCNTs/GNPs hybrid materials can improve the mechanical performance of epoxy composites in higher degree, compared with MWCNTs or GNPs particles alone.

The hexagonal boron nitride nanosheets (BN) were firstly treated by silane coupling agents 3-aminopropyltriethoxysilane (KH550) and 3-glycidoxypropyl-trimethoxysilane (KH560) to introduce some amino and epoxy (EP) groups on the BN surface. These modified BN nanosheets were incorporated into an EP matrix to prepare BN@KH560/EP composites with excellent thermal conductivity and electrical insulation properties. Results showed that the thermal conductivity of BN@KH560/EP composite with 20vol% BN dosage was found to be 0.442W/(m$\cdot$K), which was 81% higher than that of pure EP resin. Both BN/EP composites treated by KH550 and KH560 showed rather good electrical insulation properties, although the dielectric constant of BN@KH550/EP composites were slightly higher than BN@KH560/EP composites. Moreover, BN@KH560/EP composites also showed better thermal and mechanical properties than that of BN@KH550/EP composites.

Boron nitride nanosheet (BNNS) decorated with cobalt ferrite nanoparticle (CFN) to afford CFN-BNNS nanohybrid was prepared via a simple hydrothermal route and was well characterized. Subsequently, the as-prepared CFN-BNNS nanohybrid was incorporated into epoxy resin (EP) with the introduction of a weak rotary magnetic field to achieve order orientation, in order to reduce the fire risk and toxic hazards using enhanced shielding effect of BNNS upon combustion. Findings demonstrate that the CFN-BNNS nanohybrid is composed of CFN nanoparticle uniformly dispersed on BNNS surface. Thermal analysis and cone calorimeter data show that the CFN-BNNS nanofiller among EP matrix contributes to improving the char residues and mechanical properties of EP and reducing its fire risk as well as toxic hazards, especially the ordered one is advantageous over the disordered one in reducing the fire risk and toxic hazard. This is because, on the one hand, the orderly aligned BNNS as the physical barrier can more effectively prevent the transfer and diffusion of oxygen and heat. On the other hand, CFN can catalyze the degradation of EP to afford excessive chars on polymer surface; and it is also liable to decomposition during combustion, thereby generating ferrite species to promote EP degradation as well as cobalt species to enhance the oxidation of CO.

An inorganic–organic nanohybrid flame retardant, HNT@CS@Fe₃O₄, is prepared by Halloysite nanotubes (HNT) as nanotemplate, chitosan (CS) as char-forming agent and ferroferric oxide (Fe₃O${}_4)$ playing in a catalytic role, aiming to endow enhanced flame-retardant performance of its nanohybrid. Results show that HNT@CS@Fe₃O₄ nanohybrids have a corn-like structure and can significantly improve the flame retardancy and thermal stability of epoxy resin (EP). Especially, the initial thermal degradation temperature of EP/HNT@CS@Fe₃O₄ is significantly improved by $24^{\circ }$C relative to pure EP, and the residual carbon yield under air atmosphere is 8.8wt.%, which is significantly higher than other EP composites, indicating a higher thermal stability is offered by the as-prepared nanohybrid. The limiting oxygen index of EP/10HNT@CS@Fe₃O₄ is 31.3%, which is 10.2% higher than that of pure EP. Meanwhile, the HNT@CS@Fe₃O₄ nanofiller reduces the peak heat release rate, CO production and peak smoke production release of EP nanocomposite by 32.0%, 44.0% and 33.0% in a cone calorimeter test, respectively. This is because the HNT-based composite can form a three-dimensional network structure into the EP matrix to inhibit heat release and diffusion of flammable moieties upon burning of EP. In the meantime, the incorporated Fe₃O₄ nanoparticle can in situ catalyze the charring of CS and EP matrix on the surface of HNT during the combustion process, which also contributes to the significantly increased fire safety of EP.

Polyamic acid (PAA) containing aromatic ester was synthesized and used to modify the epoxy resin (E-51)/PAA curing system. The mechanical properties, dynamic mechanical properties, fracture surface morphology, and thermal properties of the E-51/PAA curing systems were systematically investigated. Experimental results revealed that the impact strength of the cured systems modified with PAA are 3 to 4 times higher than that of the unmodified system, and enhanced the thermal decomposition temperature by about 15°C, while the storage modulus is also higher than that of the unmodified system, and the fracture surfaces of modified systems display tough fracture feature.

This work outlines the characterization of epoxy resin [Bisphenol A-(epichlorhydrin): epoxy] and hardener [$N$(3-dimethylaminopropyl)-1,3-propylenediamine] with various inorganic nano-fillers. Dielectric characterizations of epoxy, hardener, neat epoxy (epoxy + hardener) and nano-epoxy (nano-filler + neat epoxy) composites loaded with 1 wt.% of inorganic nano-fillers (SiO₂, Al₂O₃, TiO₂ and ZnO) were carried out using precision LCR meter, over the frequency range of 1 kHz–2 MHz at a constant temperature of 300.15 K. The structural information of nano-fillers, neat epoxy and nano-epoxy composites was understood by Fourier transform infrared spectroscopy and by XRD. Moreover, hardness and shear strength (shear punch) were also determined in order to gain additional information about the mechanical properties of epoxy composite. Influence of inorganic nano-fillers on the dielectric properties, structural chemistry and mechanical properties of neat epoxy composite is discussed thoroughly in this study.

The silicone resin-modified epoxy resin-based flame retardant thermal insulation coating was prepared from epoxy resin as the main film-forming agent, silicone resin diluted with isopropanol as a copolymerization modifier, ammonium polyphosphate (APP) as dehydration catalyst, melamine (MEL) as foaming agent, pentaerythritol (PER) as char forming agent, and palygorskite and sepiolite as fillers. The effect of silicone resin on the flame retardancy, physicochemical properties and mechanical properties of the coatings were investigated by large plate combustion, ultimate limiting oxygen index (LOI), vertical combustion, cone calorimetry, X-ray diffraction (XRD), Fourier infrared analysis, thermogravimetric differential scanning calorimetry analysis, N₂ absorption and desorption test, scanning electron microscopy (SEM), and tensile, flexural, compressive strength tests. The addition of silicone resin not only accelerated the thermal reaction of the coating when exposed to heat, but also improved the thermal stability and oxidation resistance of the coating. The silica generated by the decomposition of silicone resin not only increased the residual char content of the coating but also optimized the structure of the coating. The surface of residual char was denser, and the internal pore structure was finer and high-density, which effectively reduced the smoke emission of the coating, enhanced the anti-ablation effect, improved the insulation effect, and increased the mechanical performance. Through comprehensive comparison, when the amount of silicone resin added was 20wt.%, the performance of E80S20 coating was the best. After 2h of butane flame ablation, the backside temperature was just 198.8^∘C with no molten pits. The peak heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and peak smoke production rate (PSPR) were significantly improved, with 17.3%, 33.8%, 32.0%, and 49.2% lower than those of blank sample E10S0. The LOI value of E80S20 was 32.5%, while that of the blank sample was just 20.8%. After combustion, the mass of the residual char and the Brunauer–Emmet–Teller (BET) surface area of E8020 was 15.8% and 256% higher than those of E10S0. Besides, the tensile, bending and compressive strengths of E80S20 were 23.7, 36.2, and 79.3MPa, which were 3%, 2.6%, and 13.1% higher than those of E10S0. Corrosion resistance tests show that the coating is suitable for aqueous environments but not for acidic or alkaline environments. Finally, the flame retardant mechanism of E80S20 coating is summarized into four types: cooling insulation, vapor phase flame retarding, condensed phase flame retarding, and reinforced flame retarding.