Mechanical Properties Of Epoxy Resin Research Articles

Nickel hydroxide and zinc hydroxystannate dual modified graphite carbon nitride for the flame retardancy and smoke suppression of epoxy resin

A functionalized graphite carbon nitride (g-C3N4) nanosheet was prepared by coprecipitation method. and its effect on the thermal stability, flame retardancy and mechanical properties of epoxy resin (EP) was investigated. Thermogravimetric analysis (TGA) results showed that the char residue of EP g-C3N4/β-Ni(OH)2/ZHS composite increased significantly. The result of the hybrids on the fire hazard of EP showed that the combination of g-C3N4, β-Ni(OH)2 and zinc hydroxystannate (ZHS) was more advantageous than a single nano-component in reducing the fire hazard of EP. The peak heat release rate, total heat release, smoke production rate and total smoke production values of the EP/g-C3N4/β-Ni(OH)2/ZHS composite were reduced to 761.9 kW/m2, 86.9 MJ/m2, 0.31 m2/s and 32 m2 which were 39.2%, 15.5%, 39.2% and 14.2% lower than those of EP, respectively. The addition of ternary hybrid reduced the mechanical properties, but it was improved compared with the use alone. Furthermore, based on the analysis of the char residue of the condensed phase, the possible flame retardant mechanism was proposed.

Enhancement of mechanical behavior of FRP composites modified by silica nanoparticles

To enhance the mechanical behavior of fiber-reinforced polymers (FRPs), the mechanical properties of epoxy and vinyl ester resin and two types of FRP modified by silica nanoparticles at 1, 2, 3, and 4 wt% are investigated herein. Fracture toughness tests of the casting resin were conducted, and scanning electron microscopy (SEM) was performed to identify the fracture surface and toughening mechanism. Damage mechanisms of resin with nanoparticles were analyzed and differences owing to varying nanoparticle contents were identified. Impregnated fiber roving with modified resin was studied for enhancements in tensile strength and stiffness. Results showed that the addition of silica nanoparticles to the epoxy/vinyl ester resin improved the mechanical properties, which reached the maximum at the nanoparticle content of 3 wt%. The tensile, flexural, and impact strengths of the epoxy resin increased by 26%, 6%, and 49%, respectively, compared with the control epoxy resin. Furthermore, the corresponding enhancements of the vinyl ester resin are 17%, 17%, and 94%. At the same particle content, the fracture toughness of the epoxy and vinyl ester resins are increased by 12% and 20%, respectively. SEM of the fracture surface reveals a relatively rough surface with tortuous cracks, thereby resulting in a higher fracture toughness of the modified resin. The tensile strength of the impregnated basalt fiber roving made of the modified vinyl ester resin increased, and results show an 18% increase at the particle content of 3 wt%. Meanwhile, the adoption of epoxy resin with silica nanoparticles resulted in the basalt and impregnated carbon fiber roving achieving higher tensile strength and stiffness compared with those without nanoparticles.

Thermo Mechanical behaviour of Phenol Novolac Resin and Unsaturated Polyester Toughened Epoxy using nano Bentonite and Silica Nanoparticles

Phenol novolac epoxy resin is a polymer matter which its properties can be modified for industrial needs. In this research, nanocomposites of phenol novolac epoxy resin and unsaturated polyester are made nano Bentonite and silica nanoparticles as filler. For this purpose, effect of nanoparticles percent on nanocomposite formation is studied and their physical, mechanical and thermal properties are obtained. The presence of unsaturated polyester in this process forms a cross-link capable of improving the physical and mechanical properties of epoxy resin. Fracture behavior was determined by a SEM device. Moreover, TGA, DSC, impact tests and bending test were applied for data analysis. When process ability is growing, moisture absorption decreases. Fracture toughness was also evaluated in a stoichiometric network. Physical and mechanical properties improve significantly with increasing nanoparticles. The most important reason for using this nanocomposite is its high resistance to corrosion.

Fire‐retardant carbon/glass fabric‐reinforced epoxy sandwich composites for structural applications

AbstractIn this study, the fire‐retardant performance of lightweight sandwich composites, with modified epoxy impregnated carbon and glass fabric reinforcements and an aluminum honeycomb core, is investigated. The fire‐retardant performance of the fabricated sandwich composites is improved by treating carbon fiber reinforcements with phosphoric acid, and by impregnating the epoxy matrix with different loadings of ammonium polyphosphate (APP) fire‐retardant additive. The laboratory aging behavior of sandwich composites is also carried out to further investigate the degradation resistance of the panels under extreme conditions. Fire and mechanical properties of epoxy and sandwich panels are investigated using UL‐94, limiting oxygen index (LOI), thermal gravimetric analysis, compression tests, and three‐point bending tests. In the case of sandwich composites, a maximum of 1345 and 45.2 MPa flexural and compression modulus, respectively, are achieved with 10 wt% APP content in epoxy. Maximum 30% and 33% LOI values are achieved with 10% APP content in the epoxy and sandwich panels, respectively.

Synthesis and application of thermal latent initiators of epoxy resins: A review

AbstractEpoxy resin, which is extensively used in civil and industrial applications, shows excellent comprehensive performance, especially as a polymer matrix used in fiber‐reinforced composites. A thermal latent initiator, used as an epoxy curing agent, has high storage stability and is widely applied in the preparation of epoxy‐based blends and fiber‐reinforced composites. In this review, the basic properties of epoxy resins and commonly used curing agents are discussed while progress on the synthesis of thermal latent initiators is reviewed in detail. Moreover, the curing mechanisms, thermal stability, and mechanical properties of epoxy resins with thermal latent initiators are also discussed.

Incorporation of Palm Fiber to Enhance the Mechanical Properties of Epoxy

In the recent years, the work in composite industry needed new ecofriendly resources to improve the original properties of current materials. Many researches attempted to find alternative additives to be used with the current systems which provide a new material that is environmentally friendly and has better performance than the synthetic counterparts. This paper presents the study of mechanical characteristics, including bending, impact, tensile and hardness tests, of date palm fiber (DPF)/ epoxy composite. The composite plate was constructed by hand-layup technique. The filler content values (wt %) were 5%, 10%, 15% and 20%. Young's modulus, impact strength and hardness were shown to be increased with increasing fiber content. Tensile strength was increased only using 5% and 10%, whereas it was decreased using fiber content.

High dielectric constant epoxy nanocomposites based on metal organic frameworks decorated multi-walled carbon nanotubes

The interfacial region between nanofillers and polymer matrix plays a crucial role in determining the dielectric and mechanical properties of dielectric nanocomposites. A new strategy using metal–organic-framework (MOF) as a modifier to decorate multi-walled carbon nanotubes (MWCNTs) to achieve high-k polymer nanocomposites is introduced. The MOF-decorated MWCNTs serve both as a curing agent and as a nano-filler to enhance dielectric, thermal and mechanical properties of epoxy. The organic component in the MOF can trigger the crosslinking of epoxy resins, leading to good dispersion of MWCNTs and strong covalent bonding between MWCNT-MOF and the epoxy matrix. It is found that covalent bonding between MOF–epoxy significantly reduces both dielectric loss and coefficient of thermal expansion (CTE), while increasing the elastic modulus of epoxy. Two types of MWCNT-MOF hybrids with distinctly different morphologies were prepared to determine their influences on dielectric and mechanical properties. The usefulness of the present approach for the preparation of multi-functional polymer nanocomposites is discussed.

In-situ growth of metal-organophosphorus nanosheet/nanorod on graphene for enhancing flame retardancy and mechanical properties of epoxy resin

Metal phenylphosphonate (MPhP)/piperazine-reduced graphene oxide (PGO) nanomaterials with different metal centers (M = Ce, Al, Co, Zn) were facilely synthesized. We found that the morphology of metal-organophosphorus was controlled by the coordinated metal centers, trivalent metal-organophosphorus exhibited nanosheet morphology, while divalent metal-organophosphorus displayed nanorod morphology. In addition, the role of metal centers on the flame safety and mechanical performance of epoxy resin (EP) were studied. The limiting oxygen index values of EP composites with only 3 wt% of additive were increased in different levels (the CePhP-PGO/EP was increased most, up from 24.5% to 34.5%), and the MPhP-PGO/EP composites all pass UL-94 V-0 rating, which was owing to the multi-coordinating effect (physical shield of GO, the catalytic of metal and gas-phase effect of P-containing radicals). Specifically, we verified that P element of MPhP-PGO (M = Ce, Al) could act on both condensed and gas phase, while MPhP-PGO (M = Co, Zn) only acted in the condensed-phase, thus MPhP-PGO/EP (M = Ce, Al) showed better enhancing effect on flame retardancy of EP. Beyond that, MPhP-PGO/EP (M = Co, Zn) displayed more excellent mechanical properties, is due to MPhP (M = Co, Zn) (nanorod) which had good reinforcement effect to EP matrix.

An experimental and numerical investigation of highly strong and tough epoxy based nanocomposite by addition of MWCNTs: Tensile and mode I fracture tests

The present study investigates, through experimental and numerical approaches, the incorporation effect of different weight concentrations of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of epoxy. Tensile and mode I fracture tests were performed to investigate the effect of the addition of MWCNTs on Young’s modulus, Ultimate Tensile Strength (UTS), critical stress intensity factor (KIC) and critical strain energy release rate (GIC). Different carbon nanotubes (CNTs) contents were employed to compare the effect of the resulting microstructures (well-dispersed and agglomerated CNTs) on the mechanical properties. Field Emission Scanning Electron Microscopy (FESEM) and Scanning Electron Microscopy (SEM) were used for microstructural analysis and fractography. Experimental results showed that UTS was improved (28%) by incorporation of MWCNTs while the KIC and GIC were substantially increased by 192% and 614%, respectively. CNT pullout and crack bridging were the main contributing mechanisms in toughening the epoxy at low CNT contents (0.1 and 0.25 wt%). In contrast, a combination of crack bridging and crack branching was responsible for the resin toughening in the case of 0.5 wt% loading. The significant increase for KIC and GIC demonstrated the excellent performance of the dispersion approach used in this study. Finite Element modelling was used to provide a more robust analysis of the effect of CNT incorporation in tension tests and of the toughening mechanism of the nanocomposites in mode-I fracture tests.

Epoxy-functionalized polysiloxane/Nano-SiO2 synergistic reinforcement in cryogenic mechanical properties of epoxy and carbon fiber reinforced epoxy laminate

Resin matrix of carbon fiber (CF) reinforced resin laminates play a key role in transferring the external stress to carbon fibers. Especially in cryogenic environment, the mechanical properties of CF reinforced resin laminates depend largely on the mechanical properties of resin matrix. In this work, an epoxy-functional polysiloxane/Nano-SiO2 (EFPS/Nano-SiO2) was prepared to enhance the mechanical properties of epoxy resin and carbon fiber reinforced epoxy laminate at RT and cryogenic environment. The TEM images indicate that the grafting of flexible macromolecule EFPS on the surface of Nano-SiO2 can improve the dispersion of Nano-SiO2 in epoxy resin. The tensile strength of epoxy resin with 5 wt% content of EFPS/Nano-SiO2 increases by 7.95% at RT and 17.07% at 90K, fracture strain by 54.55% at RT and 26.91% at 90K, fracture toughness (KIC) by 48.82% at RT and 33.33% at 77K compared with the neat epoxy resin. The enhancement mechanism should mainly be attributed to the fact that the Nano-SiO2 particles debonding enhance the energy dissipation at crack front and the flexible EFPS significantly improves the movability of epoxy curing networks. The tensile strength of CF reinforced EFPS/Nano-SiO2 epoxy laminate shows an increase of 16.64% at RT and 25.01% at 90K, confirming that the effect of EFPS/Nano-SiO2 epoxy resin transferring the external stress from resin matrix to CF is better than that of neat epoxy resin. In addition, the mechanism of thermal cycling affecting the tensile properties of CF reinforced epoxy laminates are analyzed in detail.

The joint effect of amine and maleimide functional group in aminomaleimide on the curing kinetics and mechanical properties of epoxy resins

A new epoxy curing system, combining amine and maleimide functionality into a single molecule, was introduced to broaden current state of the art as regards epoxy, amine and maleimide systems. Curing agent aminomaleimide was tested in the curing process of several aromatic and aliphatic epoxies. Prepared mixtures in different weight (molar) ratios were investigated by nonisothermal differential scanning calorimetry to study and compare curing kinetics of different epoxies. The apparent activation energy was determined by Kissinger method, while Friedman method accompanied by Malék statistical approach was used in confirming the autocatalytic nature of epoxy curing and additional maleimide polymerization at the excess amount of aminomaleimide. Thermo-mechanical properties were determined by dynamic mechanical analysis and the effect of aminomaleimide curing agent compared to curing agent containing only amino functional groups was evaluated. Aminomaleimide showed improvement in the glass transition temperatures and higher char yields due to the involvement of maleimide moiety in the curing process. In overall, aminomaleimide showed the positive one-molecule joint effect of the amino group, behaving as an accelerator, and maleimide group, a mechanical properties enhancer.

Epoxidation of Kraft Lignin as a Tool for Improving the Mechanical Properties of Epoxy Adhesive.

Owing to its chemical structure, wide availability and renewable nature, lignin is a promising candidate for the partial replacement of fossil-based raw material in the synthesis of epoxy resins. Its poor compatibility has been reported to be one of the main drawbacks in this domain. On the other hand, a well-established modification method for lignin epoxidation has been used for many years for the improvement of lignin compatibility. However, the extent of the effect of lignin epoxidation on the improvement of bio-based epoxy mechanical properties, applied as adhesives, is still an open question in the literature. In this context, a pristine and industrial grade kraft lignin (AKL) was reacted with epichlorohydrin to yield epoxidized lignin (E-AKL) in this work. Afterwards, AKL or E-AKL were separately blended with petroleum-based epoxy resin at 15 and 30 wt% and cured with a commercial amine. The adhesive curing kinetic was evaluated using a novel technique for thermal transition characterization, Temperature Modulated Optical Refractometry (TMOR); the results showed that the incorporation of AKL reduces the crosslinking rate, and that this effect is overcome by lignin modification. Mechanical tests revealed an improvement of impact and practical adhesion strength for samples containing 15 wt% of E-AKL. These results elucidate the effect of lignin epoxidation on the application of lignin-based epoxy adhesives, and might support the further development and application of these bio-based materials.

Curing kinetics and mechanical properties of epoxy resin/1-benzyl-2-methylimidazole/isophorone diamine system

The epoxy resin of diglycidyl ether of bisphenol A (DGEBA) diluted with allyl glycidyl ether (AGE) was mainly cured by 1-benzyl-2-methylimidazole (1B2MZ). Then, the effect of isophorone diamine (IPDA) on the properties of DGEBA-AGE-1B2MZ system was investigated. The differential scanning calorimetry (DSC) results revealed that when the content of 1B2MZ was small, the epoxy groups need to be completely cured by imidazole regeneration, which would be unnecessary with the introduction of IPDA thereby alleviating the burden of 1B2MZ. The variations of the activation energy with the degree of curing determined via Ozawa–Flynn–Wall were various for the studied systems. Calculations based on the Cure Index (CI) approved that the cure states of all the composite systems were affected by the heating rate. Finally, the resin of optimal formula could be cured in 20 min at 120 °C with the best mechanical properties and the glass transition temperature (Tg) of 100.61 °C.

Investigation of Mechanical Properties of MWCNTs Doped Epoxy Nanocomposites in Tensile, Fracture and Impact Tests

The current paper was aimed to investigate the effect of addition of MWCNTs on mechanical properties of epoxy. Tensile, fracture and impact tests were carried out for mechanical characterization while the weight concentration of the MWCNTs was 0.5 wt.%. Results showed that addition of MWCNTs resulted in decreasing tensile strength of the nanocomposites, whereas an improvement appeared for fracture and impact tests. In fact, fracture toughness and impact strength of the MWCNTs/epoxy increased by 65 and 117 percentage, respectively, compared with the pristine epoxy.

A Study of Electrical and Mechanical Properties of Epoxy Resin Insulating Materials under Low Temperature

Epoxy resin insulating materials have been extensively applied to main power transmission and transformation equipment. As the use environment of power transmission and transformation equipment becomes increasingly harsh, the reliability requirement of power grids for equipment is becoming higher and higher. It’s very necessary to master electrical and mechanical properties of low-temperature epoxy resin insulating materials. Dielectric properties, power-frequency breakdown properties, power-frequency flashover properties and mechanical properties of epoxy resin insulating materials under low temperature were investigated in this paper. The study results indicate that as the temperature declines, dielectric properties of epoxy resin composite materials are slightly degraded. After the temperature drops to below -40°C, dielectric properties start being gradually recovered to the state under normal temperature; AC breakdown, AC flashover and tensile properties of the materials are gradually improved as the temperature decreases.

Anhydride-cured epoxy resin reinforcing with citric acid-modified cellulose

Herein, improvement of the mechanical properties of epoxy resin by compositing with citric acid modified cellulose (CAC) was reported. CAC were prepared from carboxyl functionalization with citric acid to increase the adhesion between cellulose and epoxy resin. The epoxy resin composites were prepared using 2,2-bis (4-glycidyloxyphenyl) propane (BADGE) as component, 4-methylcyclohexane-1,2-dicarboxylic anhydride (MHHPA) as curing agent, and cellulose or CAC as filler. The tensile strength of cellulose/epoxy resin composites were decreased with the content of cellulose increased. On the other hand, the tensile strength of CAC/epoxy resin composites were effectively increased with the content of CAC increased. Moreover, compared with pure epoxy resins and cellulose/epoxy resin composites, the Young's modulus and the toughness of CAC/epoxy resin composites significantly increased with the presence of 10 wt% CAC. SEM images showed that cellulose agglomerated in epoxy resins, in contrast, CAC dispersed uniformly in epoxy resins, determined that the adhesion between CAC and epoxy resins were improved after introduced carboxyl groups to cellulose lead to the mechanical properties improved. CAC was also used to partly replace MHHPA to decrease the usage of toxic curing agent, and the mechanical properties of CAC/epoxy resin composites increased with lower MHHPA content. These results indicated that CAC can partially take place of the conventional curing agent in composite preparation, which may further decrease the production cost and improve the mechanical properties of product.

The effect of rubber on the mechanical properties of epoxy and carbon fiber (Review)

The paper presents published data on the effect of rubber elastomers on the strength properties of epoxy resin (ES) and carbon fiber. The introduction of 10% rubbers into ES ED-20 leads to an increase in compressive strength by 50%, tensile strength by 51%, impact strength by 133% and elongation by 128%. The optimal content of rubber with carboxyl groups for the OLDEN mixture was 10-12.5%, while the increase in compressive strength was 48%, impact strength - 73% and elongation - 187%. For DER 331 resin, the study was conducted with two hardeners Piperidine and DETA. The best results for Piperidine hardener were obtained on rubber with hydroxyl groups, with its optimal content of 2.5%, impact strength increased by 170%. For the hardener DETA, the best results were obtained on rubber with carboxyl groups at its optimal content of 10%, the increase in impact strength was 66%. When modifying carbon fiber with rubbers, it leads to a significant increase in the yield strength in tension by 42%, the modulus of elasticity in bending by 63%, and with a slight loss of impact strength.

Effect of acetone on mechanical properties of epoxy used for surface treatment before adhesive bonding

A thin layer of un-cured resin over metal substrates applied by using an acetone-diluted resin solution (without hardener) has been found to be beneficial to strong adhesive bonding. The resin pre-coating (RPC) solution can effectively seal sub-surface micro-cavities and increase the substrate wettability. This study examines possible aftermath effects of the acetone dilution on mechanical properties of epoxy through comparison of samples made from as-received resin and resins diluted once and twice by acetone. RPC can be accepted with confidence in substrate pre-treatments for strong adhesive bonding if no detrimental effect on epoxy properties is observed. Fourier transform infrared spectrum (FTIR) was conducted, showing the spectrogram of the resin previously diluted by acetone was the same as that of as-received resin, i.e. no change in epoxy molecular structures after complete evaporation of acetone. Strength and modulus of elasticity measured by flexural and compressive tests were compared using samples made from as-received resin, and resins diluted once and twice by acetone. Variations among results from the three groups were less than 2%, or negligible, affirming the RPC method can be used for substrate pre-treatments and stronger adhesive bonding.

Influence of Aluminum Fine Powder Content on the Some Mechanical Properties of Epoxy and Polyester Composites

In this study, the effect of aluminum powders on the some mechanical properties of epoxy (EP) and unsaturated polyester (UPE) composites was investigated. Aluminum powders (Al) were added to polymers with (0, 1, 3 and 5) %weight percentages. epoxy/Aluminum and unsaturated polyester/Aluminum composites were fabricated by the cast molding method. Maximum fracture forces, Maximum Extensions, Yield Points, Young Modulus, Tensile Strengths, flexural strength and ultimate compressive strength tests were performed on both composites. The results showed that the tensile strength of epoxy/Aluminum composites increased with increasing of additive percentage of Al powder, and the samples of EP/Al composite gained highest values of tensile strength (22.48 MPa) at ratio percent(5%). While the tensile strength of unsaturated polyester/Aluminum composites decreased with increasing of additive percentage of Al powder. Also the results showed that the samples of EP/Al composite gained highest values of flexural strength (58.63MPa) at weight percentage (1%).While the samples of UPE/Al composite gained highest values of flexural strength (91.88 MPa) at weight Percentage (3%). Finally, the value of compressive strength decreased with increasing of additive percentage of Al powder in both of EP/Al and UPE/Al composites.

Mesoporous silica via self-assembly of nano zinc amino-tris-(methylenephosphonate) exhibiting reduced fire hazards and improved impact toughness in epoxy resin

Mesoporous silica@nano-zinc amino-tris-(methylenephosphonate) (m-SiO2@Zn-AMP) spheres were synthesized via a self-assembly process to integrate the outstanding flame retardancy, thermal stability, and mechanical properties of these materials. The results indicated that nano Zn-AMP particles were successfully deposited on the surface of m-SiO2 through electrostatic interactions. The prepared m-SiO2@Zn-AMP was utilized to improve the flame retardancy, smoke suppression, and mechanical properties of epoxy resin (EP). The storage modulus, impact, and tensile strengths of the EP with 1% m-SiO2@Zn-AMP (sample EP/1m-SiO2@Zn-AMP) were increased by 29.9, 50.0, and 23.5 %, respectively, relative to the values for untreated EP. The presence of multiple flame retardant elements (i.e. Si, P, N, and Zn) in the mesoporous spheres led to the formation of high yields of compact char residues and the release of inert substance during combustion, for high flame retardancy and efficient smoke suppression in the condensed and gaseous phase. The EP/5m-SiO2@Zn-AMP sample achieved a V0 rating in a vertical UL-94 test. Compared to untreated EP, the amount of total smoke released and the peak CO production rate of EP/5m-SiO2@Zn-AMP were reduced by 53.1 and 61.5 %, respectively. Additionally, the total heat release and peak heat release rate of EP/5m-SiO2@Zn-AMP were decreased by 45.2 and 57.8 %, respectively.