Modified Epoxy Resin Research Articles

Fabrication and Experimental Testing of Hybrid Composite Material Having Biodegradable Bagasse Fiber in a Modified Epoxy Resin: Evaluation of Mechanical and Morphological Behavior

Natural fibers such as bagasse, jute, sisal and coir are biodegradable as well as non-toxic in nature, so the use of natural fiber is safe. Bagasse contains about 50% cellulose, 25% hemicellulose, and 25% lignin. The present work has been undertaken to develop a composite using bagasse fiber as reinforcement and to study its mechanical properties, morphology, water absorption capacity and performance. The composites were prepared with different weight percentage of bagasse fiber by hand lay-up method. In the present research work, it can be concluded that with increase in wt.% of bagasse fiber in matrix material the rate of water absorption increases. Ultimate tensile strength, ultimate compressive and flexural strength of the composite are less than the pure epoxy while Young’s modulus is higher for composite. Ultimate tensile, ultimate compressive strength and flexural strength of composite is decreasing at all cross head speed with increase in wt.% of bagasse fiber while flexural strain is increasing. Scanning Electron Microscopy (SEM) showed that for 5 wt.% of bagasse fiber the binding between epoxy and bagasse fiber is better than the 10 and 15 wt.% of bagasse fiber configuration. This was because of the increase in wt.% of bagasse fiber, which results in cavities and improper binding in the composite domain. Thus, as we increase the wt.% of bagasse fiber it causes the decrease in mechanical properties of composite.

Preparation and properties of flame retardant epoxy resin modified by additive nitrogen-containing POSS-based molecule with eight DOPO units

Octa-N-phenylaminopropyl-POSS (Octa-NAPA-POSS), DOPO and paraformaldehyde were used to synthesize Octa-DOPO-POSS through the Kabachnik-Fields reaction. It was added into epoxy resin with different ratio to prepare a series of modified epoxy resin composites. The results proved that the addition of flame retardant Octa-DOPO-POSS significantly improved the thermal property, flame retardant performance and moisture resistance of epoxy resin without weakening the mechanical properties. When the addition amount of Octa-DOPO-POSS was 5 wt%, the LOI value of the cured EP/Octa-DOPO-POSS composite increased to 33.9%. Its UL-94 level reached V-0 rating, and the THR and PHRR were significantly reduced. Meanwhile, the flexural modulus and breaking elongation were improved. Moreover, as the adding amount increased the residual char yield of EP/Octa-DOPO-POSS composites also increased, while the maximum thermal weight loss rate gradually decreased. The real-time FTIR and SEM analysis of the char residue after high temperature pyrolysis proved that Octa-DOPO-POSS could promote the char formation and produce a denser char layer. Overall, the combination of POSS and DOPO at a molecular level rather than physical mixing has a positive and significant effect on the flame retardancy of epoxy resin.

A (4‐fluorophenyl)(phenyl)phosphine oxide‐modified epoxy resin with improved flame‐retardancy, hydrophobicity, and dielectric properties

AbstractThe compound (4‐fluorophenyl)(phenyl) phosphine oxide (4‐FPO) was designed, synthesized, and used in the modification of epoxy resin (EP). The 4‐FPO‐modified EP was prepared by curing the reaction mixture of diglycidyl ether of bisphenol A (DGEBA) and 4‐FPO in the presence of 4,4′‐diaminodiphenylsulfone (DDS). Compared with the unmodified EP, the limiting oxygen index value of the EP/4‐FPO‐0.6 (4‐FPO‐modified EP with 0.6 wt% of phosphorus) increased to 31.6%, and the sample achieved UL‐94 V‐0 rating. The peak of the heat release rate, average of the heat release rate, and total heat release of EP/4‐FPO‐0.6 were reduced by 39, 24, and 19%, respectively. Mechanism study showed that the quenching effect in the gas and barrier effect in the condensed phase were responsible for the enhanced flame‐retardant properties of the 4‐FPO‐modified EP. The results showed that hydrophobicity and dielectric properties of the modified EP were clearly improved.

Facile synthesis of carbon microspheres/tin ethylenediamine tetramethylene phosphonate hybrid for improving the mechanical, flame‐retardant, and thermal properties of epoxy resin

A botryoidal carbon microspheres/tin ethylenediamine tetramethylene phosphonate hybrid (CMS@TETP) was fabricated via a self‐assembly method and was applied to modify epoxy resin (EP) in order to simultaneously improve its mechanical, flame‐retardant, and thermal properties. The mechanical tests' results show that the addition of 1.0 wt% CMS@TETP endows EP with an increase in tensile and impact strengths of 24.4% and 23.1%, respectively, relative to the values of pure EP. The cone calorimeter test results reveal that CMS@TETP has better flame retardancy in EP than either CMS or TETP at the same loading level. In comparison with those of pure EP, the mean heat release rate, peak heat release rate, total heat release, and effective heat of combustion of the EP composite containing 3.0 wt% CMS@TETP (EP/CMS@TETP‐3) are respectively reduced by 49.5%, 59.1%, 47.0%, and 46.1%. The glass transition temperatures of EP/CMS@TETP composites are slightly increased than that of pure EP, indicating an increase in the thermal resistance. Thermogravimetric analysis results provide evidence that CMS@TETP has good char‐forming capacity in EP.

Synergistically optimizing interlaminar behavior of CFRP composites by simultaneously applying amino-rich graphene oxide to carbon fiber and epoxy matrix

In this study, graphene oxide (GO) with long flexible amino-rich structure, i.e., GO-COOH-T403, was prepared by grafting trifunctional polyether amine (T403) to the surface of in-situ carbonylated GO. The amino-rich GO nanosheets were employed to modify epoxy resin and fabricate multiscale carbon fiber (CF), respectively. Basing on that, carbon fiber reinforced polymer (CFRP) composites with superior interlaminar behavior were obtained via impregnating multiscale CF with the amino-rich GO modified epoxy. The interlaminar analysis indicated that simultaneously applying amino-rich graphene oxide to CF and epoxy matrix could effectively optimize the interlaminar properties of the resulting composites. Notably, the value of ILSS for multiscale CF reinforced amino-rich GO modified epoxy composites was 82.2 MPa and 32.6% higher than that single employed amino-rich GO into epoxy matrix or onto CF exhibiting a synergistic behavior. Therefore, this work was expected to provide new inspiration for developing high-performance CFRPs with excellent interlaminar properties.

Influence of Modified Epoxy Resins on Peroxide Curing, Mechanical Properties and Adhesion of SBR, NBR and XNBR to Silver Wires. Part I: Application of Monoperoxy Derivative of Epoxy Resin (PO)

The research was aimed at checking the effect of monoperoxy derivative of epoxy resin (PO) on the possibility of rubber crosslinking and a subsequent adhesion of the modified rubber to silver wires. Three of the commonly industrially used rubbers were selected for the study: styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR) and carboxylated acrylonitrile-butadiene rubber (XNBR), together with the popular, commercially available Epidian 6 epoxy resin, subjected to the functionalization. An improvement in the adhesion of rubbers to silver wires was observed when using the modified resin. In some cases, an improvement in the mechanical properties of the rubber was observed, especially when the resin was used for crosslinking together with dicumyl peroxide (DCP). Crosslinking synergy between dicumyl peroxide and the modified resin could be observed especially in the case of PO applied for peroxide curing of SBR and NBR.

Influence of Modified Epoxy Resins on Peroxide Curing, Mechanical Properties and Adhesion of SBR, NBR and XNBR to Silver Wires-Part II: Application of Carboxy-Containing Peroxy Oligomer (CPO).

This research was aimed at verifying the effect of carboxy-containing peroxy oligomer (CPO) addition on the possibility of rubber crosslinking and a subsequent adhesion of the modified rubber to silver wires. Three commonly industrially used rubbers were selected for the study: styrene–butadiene rubber (SBR), acrylonitrile–butadiene rubber (NBR) and carboxylated acrylonitrile–butadiene rubber (XNBR), together with carboxy-containing peroxy oligomer (CPO). An improvement in the adhesion of rubbers to silver wires was observed when applying the oligomeric peroxide with functional groups, with no deterioration of mechanical properties of the vulcanizates. Crosslinking synergy between dicumyl peroxide (DCP) and the modifier could hardly be observed. Nevertheless, the studies demonstrated, that to a small extent, even the CPO itself can crosslink NBR and especially XNBR, resulting in a material of notable elasticity and adhesion to silver wires.

Plasticizing effect of biodegradable dipropylene glycol bibenzoate and epoxidized linseed oil on diglycidyl ether of bisphenol A based epoxy resin

AbstractMajor limitation for use of epoxy thermosets in engineering applications is its sudden brittle failure. In the present study dipropylene glycol dibenzoate (DPGDB) based plasticizer is used to modify diglycidyl ether of bisphenol A (DEGEBA) based epoxy resin system via simple blending technique. Bio‐based epoxidized linseed oil was also used to modify epoxy resin system and compared with DPGDB modified resin. For DPGDB modified resin storage modulus and loss modulus of the epoxy system modified with 10% plasticizer increased by 7.54% and 12.24%, respectively. The primary mechanism responsible for such behavior is improved crosslinking density. With 5% plasticizer loading, flexural strength increased by 21%. There was an improvement of 312.74% in strain at failure for 10% plasticizer loading, while preserving its mechanical strength. It was found that DPGDB based modification was better than epoxidized linseed oil modification.

Mechanical Properties of Selected Epoxy Adhesive and Adhesive Joints of Steel Sheets

The article presents the issues of the mechanical properties of epoxy adhesives and the adhesive joints strength of steel sheets which were made using the epoxy adhesives. The aim of the paper is to study the mechanical properties of epoxy adhesive of different epoxy resin/curing agent ratios (within and above the recommended stoichiometric ratio) and their effect on mechanical properties of adhesive joints of steel sheets. In experimental tests three types of epoxy adhesives, containing a low molecular weight epoxy resin based on bisphenol A and polyamide curing agent, were used. A single-lap adhesive joint type of stainless-steel sheets was also applied. Two types of strength test were used: the compressive strength tests (DIN EN 196-1) for epoxy adhesive samples and the shear strength tests (DIN EN 1465) for adhesive joints. Both the analysis of the strength results of the samples of epoxy adhesive and adhesive joints as well as the failure analysis was carried out. On the basis of the results of strength tests it can be stated that the greatest deformation occurred for the samples of epoxy adhesive containing the modified epoxy resin (epoxy number—0.40) and the polyamide curing agent, and the smallest for the samples of epoxy adhesive containing the basic epoxy resin (epoxy number—0.49–0.52) and the polyamide curing agent. The epoxy adhesives with a smaller amount of curing agent were characterized by higher strength. This applies to all analyzed epoxy resins. The same dependences were obtained for the strength of adhesive joints of steel sheets made of the analyzed epoxy adhesive.

Mechanical Properties of the Carbon Nanotube Modified Epoxy-Carbon Fiber Unidirectional Prepreg Laminates.

The effect of plasma treatment of the multi-walled carbon nanotube (MWCNT) surface on the fracture toughness of an aerospace grade epoxy resin and its unidirectional (UD) carbon fiber prepreg laminates has attracted scientific interest. A prepreg route eliminates the possible risk of carbon nanotube filtration by unidirectional carbon fibers. X-ray photoelectron spectroscopy results suggested that oxygen atom concentration at the nanotube surface was increased from 0.9% to 3.7% after plasma modification of the carbon nanotubes. A low number (up to 0.5 wt.%) of MWCNTs was added to epoxy resin and their carbon fiber prepreg laminates. Transmission electron micrographs revealed that the plasma treatment resulted in a better dispersion and distribution of MWCNTs in the epoxy resin. Plasma-treated MWCNTs resulted in a more pronounced resistance to the crack propagation of epoxy resin. During the production of the reference and nanotube-modified prepregs, a comparable prepreg quality was achieved. Neat nanotubes agglomerated strongly in the resin-rich regions of laminates lowering the interlaminar fracture toughness under mode I and mode II loading. However, plasma-treated nanotubes were found mostly as single particles in the resin-rich regions of laminates promoting higher energy dissipation during crack propagation via a CNT pull-out mechanism.

New Epoxy with Self-Repairing Properties of Environmental-Friendly Building Structure Adhesives

Abstract With the rapid increase in newly constructed buildings, the number of old buildings that need reinforcement and repair also increases due to aging, accidental damage, or modernization refurbishment. Likewise, the demand of the building adhesive keeps growing with the expansion of its application scope. However, because of the recognition of many demerits of the existing epoxy building adhesives (e.g., low bonding strength, high frangibility, and low elasticity modulus), the need for a new environment-friendly building structure adhesive has been growing steadily. In this paper, the potential of nano-scaled rubber (VP-501: diameter of ~70 nm) was investigated with respect to its capacity to enhance the capacity of the epoxy resin with respect to the static tensile, fracture toughness, and dynamic mechanical properties. Further, its effects on the thermal stability and glass-transition temperature change were also examined with the content of toughening agent. Our discussion was extended further to describe the mechanism under which the toughness and heat resistance of the modified epoxy resin are improved.

Thermal and Sound Absorption Properties of Porous Epoxy Resin Modified by Organic Silicon

The organic silicon modified epoxy resin is prepared by the dehydration reaction between diphenyl silicon diol and the hydroxyl group on the epoxy resin, and the foamed material is prepared by the mass ratio NaHCO3:H:OBSH=5:5:3 composite foaming agent. The foams was characterized by infrared spectroscopy (FT-IR), Thermogravimetric (TG) and standard wave tube method. The results indicate that: The heat resistance of the cured resin of modified resin is better than that of cured epoxy resin, and the sound absorption coefficient of the sample with opening rate of about 54.4% can reach more than 0.8 for high frequency sound waves (>1000 Hz).

Preparation of Inorganic Filler Modified Epoxy Resin Adhesive and Study on Its Compatibility with UDMH

Epoxy resin adhesive have many advantages that other adhesives do not have, and are widely used in various fields. At the same time, it is also a thermosetting resin with high crosslinking density. Its cured product is brittle, low impact strength, and easy to crack. These shortcomings limit the further application of epoxy resin. This article takes the plugging agent of UDMH as the starting point. Epoxy resin adhesive toughened and modified with two kinds of inorganic fillers, nano-titania and micro-alumina, were prepared and study the compatibility of modified epoxy resin adhesive with UDMH. It is found that under certain conditions, the silane coupling agent KH570 can undergo a grafting reaction with the hydroxyl groups on the surface of nano-TiO2 to improve its lipophilic and hydrophobic properties, and the effect is better than KH560, KH550; Through FT-IR, SEM, TG and other characterization methods, it is found that when the content of coupling agent is 15%, the effect of surface modification is the best. In the preparation of two kinds of inorganic filler modified epoxy adhesives, it is found that when the content of nano-TiO2 is 3%, the toughening effect is the best, and the impact strength can reach 36.78 KJ/m2; When the content of micro alumina is 60%, the toughening effect is best, and the impact strength can reach 28.43 KJ/m2. In general, the toughening effect of using nano-TiO2 is significantly better than that of alumina. In the study of the compatibility of the two kinds of filler modified epoxy resin adhesives with UDMH, it is found that when nano-titanium oxide is used as the filler, the compatibility of epoxy adhesive and UDMH is improved. However, when micro-alumina is used as the filler, the compatibility of epoxy resin adhesive and UDMH becomes worse.

Flame retardancy, thermal decomposition and mechanical properties of epoxy resin modified with copper N, N’-piperazine (bismethylene phosphonate)

A metal–organic phosphonate, i.e., copper N, N’-piperazine (bismethylene phosphonate) (CuPB) was synthesized and utilized to modify epoxy resin (EP). The flame retardancy, thermal decomposition and mechanical properties of EP/CuPB composites are overall evaluated, and the mechanism is tentatively discussed. The results reveal that EP containing 3.0 wt% CuPB (EP/CuPB-3) passes UL-94 V-0 grade with an increased limiting oxygen index of 28.5%. The peak heat release rate, total heat release, total smoke release and peak CO production rate of EP/CuPB-3 in cone calorimeter test are, respectively, reduced by 43.5%, 28.0%, 37.3% and 51.9%, compared to that of pure EP. Besides, a decreased mass-loss rate (16.2% min−1) and an increased char yield (26.8%) of EP/CuPB-3 in the thermogravimetric analysis are achieved as a result of the char-promotion function of CuPB. Satisfactorily, the thermal resistance of EP/CuPB composites is slightly improved with an increased glass transition temperature, and the mechanical properties including tensile and impact strengths are not much affected.

Dynamic Mechanical Characteristics of Fractured Rock Reinforced by Different Grouts

In order to investigate the dynamic mechanical properties of the fractured rocks reinforced with different slurries, the prefractured and grouted sandy mudstone specimens were tested on a Split Hopkinson Pressure Bar (SHPB), and their dynamic failure processes were shot via a high-speed camera. The test results showed that under dynamic loading, grouting reinforcement can relieve the rock failure at the fracture part. With the increase of the impact speed, the dynamic specific strength of the modified epoxy resin grouting increases from 0.85 to 1.01, and its specific strain rate increases from 1.09 to 1.04; the dynamic specific strength and specific strain rate of cement slurry grouting increase from 1.78 to 0.95 and from 0.60 to 0.98, respectively. As a whole, the specimen reaches or approaches the dynamic parameters of the intact rock specimen after grouting repair, the stability of the rock reinforced by modified epoxy resin grouting is superior to that of the rock reinforced by cement slurry grouting, and the latter can acquire high dynamic strength under low-speed impact. The improved damage-type Zhuwangtang (ZWT) model can be used to describe the dynamic mechanical behaviors of the fractured rocks reinforced by grouting very well.

Research Progress in Modification of Epoxy Resins with Hyperbranched Polyesters

Research Progress in Modification of Epoxy Resins with Hyperbranched Polyesters

Polybenzoxazine-modified epoxy resin: thermal properties and coating performance

In this investigation, a sample of epoxy resin was modified with different weight ratios (2, 5, 10, 15, and 20%) of a benzoxazine and thermally cured to form films; EB02, EB05, EB10, EB15, and EB20, respectively. The curing reaction of the benzoxazine molecules and epoxy prepolymer was monitored by the Fourier transform infrared (FTIR) spectroscopic analysis. The examination of anticorrosion performances of the individual films by the method of electrochemical impedance spectroscopy (EIS), was achieved by, respectively, coating the films on stainless steel (SS) substrates. The water absorption behavior of the individual films also was examined by water sorption (WS) analysis. The water intake of the tested modified-epoxy resin shows a linear dependence on the amount of polybenzoxazine in each of the samples. Better coating performances are seen, from the EIS results of modified epoxy films in comparison to the pure epoxy resin. However, the EB20 shows outstanding corrosion prevention property with excellent hydrophobicity.

Multi-effects of atmospheric He/CF4 plasma jet treatment on the surface properties of epoxy resin

Surface fluorination by low-temperature plasma treatment is proved to be a useful method to improve surface electrical strength of insulating materials. The electrical performances of modified materials deeply depend on the operation parameters during surface modification. It is necessary to find out the physical and chemical changes on the surface properties of modified materials systematically combined with different parameters. In this paper, an atmospheric pressure plasma jet (APPJ) fed with He/CF4 mixtures is utilized for treatment of epoxy resin (EP). The surface properties of modified epoxy resin are evaluated by the water contact angle (WCA), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results show that the He/CF4 APPJ has multi-effects on the surface properties of epoxy resin. It means that some different changes are found under different operation parameters. The multi-effects are mainly caused by the various physical and chemical processes in the interface between plasma and material surface, and they can be adjusted by changing the plasma exposure time, the applied voltage and the CF4 volume fraction. The results can offer an evidence for the mechanisms of the enhanced surface electrical strength using plasma-based surface fluorination.

Phosphorus and bromine modified epoxy resin with enhanced cryogenic mechanical properties and liquid oxygen compatibility simultaneously

Herein, epoxy resins for composite liquid oxygen (LOX) fuel tanks are modified with phosphorous flame retardant (DOPO) and brominated epoxy resin (EX48). With the incorporation of DOPO and EX48, the processing properties requirements for the hot-melt prepreg are contented with the significantly enhanced viscosity of the modified epoxy resin. At the same time, the tensile performance, flexural performance and fracture toughness of epoxy resin at room temperature and 90 K are improved with the introduction of DOPO and EX48. In addition, the epoxy resin of EP/P7.7/Br40 offers a highest limited oxygen index of 33.5% and a lowest LOX impact sensitivity of 5% with the eliminated LOX incompatible reactions including explosion and combustion. Consideration of the excellent cryogenic mechanical properties and LOX compatibility, combined with ideal viscosity for hot-melt prepreg preparation, the epoxy resin modified with DOPO and EX48 simultaneously is attractive as the polymer matrix for composite LOX fuel tanks.

Impact of nano-silicon dioxide on mechanical properties of carbon fabric reinforced epoxy composites

Nanoparticles could improve the mechanical properties of polymer based composites due to synergy of higher filler-matrix interaction and better load transfer from matrix to the fillers. Epoxy resin has high strength and modulus, and good adhesion strength, which makes it attractive for several industrial applications. To improve interfacial bonding between epoxy and silicon dioxide (SiO2), surface treatment of SiO2 is done using acetone and silane coupling agents. To improve SiO2 dispersion in epoxy matrix, the epoxy matrix is modified by mixing with amine containing liquid rubber. Ultrasonication process has been used for uniform mixing of SiO2 in the modified epoxy resin. Carbon fabric reinforced epoxy (CF/Ep) composite with surface treated nano- SiO2 are fabricated using vacuum bagging technique followed by hot press. The effect of silane treated nano- SiO2 with varying filler loadings from 0.5 to 3 wt% on the static mechanical properties such as hardness, tensile, and flexural properties are characterized following ASTM standards. The experimental results show that the inclusion of silane coupling agent increased the interfacial bonding between nano- SiO2 particles and the epoxy resin so that the surface hardness, tensile and flexural properties are improved.