Epoxy Clay Nanocomposites Research Articles

Synthesis and Characterization of Soy-based Nanocomposites

Soy-based nanocomposites were synthesized using soy resin and montmorillonite clay. Two types of dispersion techniques, pneumatic and sonication, were carried out to disperse the nanoclay into the soy-based epoxy resin. Tensile testing of the nanocomposites showed that the nanoclay improved the modulus and the strength by 625% and 340%, respectively. Exfoliation of the nanoclay was investigated by X-ray diffraction. The curing mechanism of soy epoxy resin with different amounts of montmorillonite was studied using differential scanning calorimetry and Fourier transform infrared spectroscopy. Rheological measurements were also conducted to find the suitability of using the soy-based epoxy clay nanocomposites toward composite manufacturing applications. The dielectric constant and the loss factor were also investigated. These soy-based nanocomposites hold great promise as environmentally friendly and low cost materials for structural applications.

Preparation and Properties of Epoxy‐Clay Nanocomposites

Epoxy‐clay nanocomposites were synthesized to examine the effects of adding different contents of nanoclays on the physical, mechanical, and thermal properties of the epoxy resin system used in composite pipes manufacturing. Diglycidyl ether of bisphenol‐A (epoxy) with a cycloaliphatic amine heat curing hardner was reinforced by 1–7 wt.% of an organically modified type of montmorillonite. SEM results showed the change in failure of epoxy from brittle to tough mode by addition of nanoclays. X‐ray results indicated some degree of exfoliation by 1 wt.% clay and a decrease in d‐spacing in higher clay loadings after that. The heat‐distortion temperature of epoxy-clay nanocomposites increased from 125.5 to 138.7°C with 3 wt.% organoclay loading. Tensile and flexural modulus increased with increasing clay loading in this type of nanocomposite, but addition of organically modified clay decreased the tensile and flexural strengths and tensile elongation at break. Addition of 7 wt.% nanoclay improved the impact strength by 25.6%.

Water uptake of epoxy–clay nanocomposites: Model development

Models for the water uptake behavior of epoxy–clay nanocomposites are presented. Diffusion models for epoxy including Fick’s law, the Langmuir model of diffusion, diffusion with time-varying diffusivity, and diffusion models for composites are reviewed. Models for the diffusivities of exfoliated and intercalated nanocomposites are developed.

Water uptake of epoxy–clay nanocomposites: Model development

Models for the water uptake behavior of epoxy–clay nanocomposites are presented. Diffusion models for epoxy including Fick’s law, the Langmuir model of diffusion (LMD), diffusion with time-varying diffusivity (DTVD), and diffusion models for composites are reviewed. Models for the diffusivities of exfoliated and intercalated nanocomposites are developed.

Clay-epoxy nanocomposites: Processing and properties

The work described in this paper is focused on evaluating the effect of the processing method and nanoclay (montmorillonite) content on the tensile, compressive, and impact properties of clay-epoxy nanocomposites. Nanocomposites are synthesized by two methods: mechanical mixing and shear mixing. Both these methods are capable of producing bulk quantities of clay-epoxy nanocomposites. X-ray diffraction analysis indicates that the nanoclay has exfoliated in the mechanically mixed specimens. Results show that as nanoclay content increases the tensile modulus increases for both mechanically and shear mixed specimens, while the compressive modulus remains largely unchanged. The total energy absorption under impact loading is found to be higher in mechanically mixed specimens.

Study on the thermal and mechanical properties of epoxy–nanoclay composites: The effect of ultrasonic stirring time

Epoxy–clay nanocomposites were synthesized with organophilic montmorillonite and diglycidyl ether of bisphenol A by using the in-situ polymerization under ultrasonic treatment. The clay layers were found to be separated further with the increase in the duration of ultrasonic stirring as measured from the X-ray diffraction measurements. Thermogravimetric analysis provided the fact that the maximum thermal decomposition temperatures increased with the increase in the duration of ultrasonic stirring. However, both the glass transition temperature and the storage moduli of the composites decreased with the increase of ultrasonic stirring time as measured from the dynamic mechanical analysis.

Epoxy-silicate nanocomposites: Cure monitoring and characterization

Epoxy-clay nanocomposites were prepared with organically modified layered clay with varying clay contents (1–8 wt.%). Neat resin and nanocomposite were characterized using different techniques. At first, the effect of nanoclay concentration on the cure behaviour was investigated using an on-line dielectric cure monitoring technique. Differential scanning calorimetry (DSC) was used to verify the dielectric measurement results. Furthermore, mechanical and thermal properties were studied using tensile test and Dynamic Mechanical Analysis (DMA), respectively. Experimental results showed that properties of the epoxy were changed evidently because of the nanoclay loading. The tensile modulus of the nanocomposites increased by 47%, however, no improvement in tensile strength and glass transition temperature ( T g) was observed. Fracture surface of the tensile samples were analyzed by Scanning Electron Microscope (SEM). The nanocomposites structures were characterized with Wide Angle X-Ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM), which revealed the intercalated morphology of clay layers in the epoxy resin systems.

Mechanism of Fatigue Failure of Clay–Epoxy Nanocomposites

This work investigates the fatigue behaviour and the mechanism of fatigue failure of an epoxy resin with a dispersion of modified layered silicates in the polymer matrix. The fatigue properties are very important for structural application of nanocomposite materials. Clay-epoxy nanocomposites were successfully synthesized with a commercially available 1-Methylimidazole curing agent. The XRD and TEM findings demonstrated a pattern of clay morphology typically found in nanocomposite systems. The fatigue performance and fatigue failure mechanism of the clay-epoxy materials were studied under repetitive bending loads. The results showed that the fatigue life of filled epoxy improved significantly at strain amplitudes below a threshold value. The E-SEM observations of the epoxy and the clay-epoxy fracture surfaces showed different patterns. In conclusion, the addition of silicate strongly determines the fracture mechanism and enhances the fatigue performance.

Thermal, mechanical and vibration characteristics of epoxy-clay nanocomposites

Diglycidyl ether of bisphenol-A (DGEBA) epoxy resin system filled individually with organoclay (OC) and unmodified clay (UC) were synthesized by mechanical shear mixing with the addition of diamino-diphenylmethane (DDM) hardener. The unmodified clay used was Na+-Montmorillonite (MMT) and the organoclay was alkyl ammonium treated MMT clay. The reinforcement effect of OC and UC in the epoxy polymer on thermal, mechanical and vibration properties were studied. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) were used to study the structure and morphology of nanocomposites. Curing study shows that the addition of OC in epoxy resin aids the polymerization by catalytic effect, and UC addition does not show any effect in the curing behavior of epoxy polymer. Thermogravimetry analysis (TGA) shows enhanced thermal stability for epoxy with OC fillers than that of epoxy with UC fillers. The epoxy with OC fillers shows considerable improvement on tensile and impact properties over pure epoxy polymer and epoxy with UC fillers. The improvement in tensile and impact properties of nanocomposites is supported with the fracture surface studies. Epoxy with OC fillers shows enhanced vibration characteristics than that of the pure epoxy polymer and epoxy with UC fillers.

Effect of processing parameters and clay volume fraction on the mechanical properties of epoxy-clay nanocomposites

The influence of processing parameters and particle volume fraction was experimentally studied for epoxy clay nanocomposites. Nanocomposites were prepared using onium ion surface modified montmorillonite (MMT) layered clay and epoxy resin (DEGBF). Two different techniques were used for dispersing the clay particles in the epoxy matrix, viz. high-speed shear dispersion and ultrasonic disruption. The volume fraction of clay particles was systematically varied from 0.5 to 6%, and mechanical properties, viz. flexural modulus and fracture toughness, were studied as a function of clay volume fraction and the processing technique. The flexural modulus was observed to increase monotonously with increase in volume fraction of clay particles, while, the fracture toughness showed an initial increase on addition of clay particles, but a subsequent decrease at higher clay volume fractions. In general, nanocomposites processed by shear mixing exhibited better mechanical properties as compared to those processed by ultrasonication. Investigation by X-ray diffraction (XRD) revealed exfoliated clay structure in most of the nanocomposites that were fabricated. Morphologies of the fracture surfaces of nanocomposites were studied using a scanning electron microscopy (SEM). Presence of river markings at low clay volume fractions provided evidence of extrinsic toughening taking place in an otherwise brittle epoxy.

The effect of shear forces on the microstructure and mechanical properties of epoxy–clay nanocomposites

AbstractThe objective of this work is to understand the effect of shear force on the properties of epoxy–clay nanocomposites. The shear force was controlled by changing the revolutions per minute on a mechanical mixer. Differences in the aspect ratio of clay layers and differences of clay particle distribution in the epoxy matrix were caused by shear force. Shear force mechanism on epoxy–clay nanocomposites' intercalation/exfoliation were compared with the other mechanism already suggested. X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy were utilized to investigate the degree of exfoliation and morphology. The mechanical and thermal properties were also studied to demonstrate the effect of shear force. This study revealed that appropriate shear force and mixing time on nanocomposite preparation was required to achieve the desired properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3465–3473, 2006

The Preparation and Characterization of a Novolac Cured Epoxy-Clay Nanocomposites

ABSTRACTIntercalated or exfoliated nanocomposites were composed by the novolac cured epoxy and one of three different kinds of layered silicates, such as montmorillonite (PK-802), saponite (Semecton-SA) and nontronite (PK-805). The bi-functional modifiers (PI/BEN or MI/BEN) with different ratio, which contained one of the promoters (2-phenylimidazole, PI and 2-methylimidazole, MI) of epoxy and benzalkonium chloride (BEN), were intercalated into the gallery regions of pure clays at the same time and followed by a crosslinking reaction. The properties of novolac cured epoxy/clay nanocomposites were characterized by wild-angle X-ray diffraction (WAXRD), thermal analysis (TGA/DSC), coefficiency of thermal expansion (TMA), mechanical properties (DMA), and transmission electron microscopy (TEM). According to the measurement, these novolac cured epoxy-clay nanocomposites have shown the significant improvement in the thermal, mechanical and barrier properties.

Hydrothermal effects on the thermomechanical properties of high performance epoxy/clay nanocomposites

AbstractThe effects of hydrothermal ageing on the thermomechanical properties of high performance epoxy and its nanocomposite were studied. The epoxy–clay nanocomposite was prepared through a recently developed “slurry‐compounding” approach. The cured samples were immersed in distilled water at 60°C for different periods of time before subjecting to characterization. The storage modulus, relaxation behavior, fracture toughness, and tensile properties were investigated. It was found that the storage modulus and α‐relaxation were strongly affected by water uptake, while the fracture toughness and Young's modulus were less influenced. Dependence of tensile strength and strain at break on water uptake was found to be different in neat epoxy and epoxy–clay systems. POLYM. ENG. SCI., 46:215–221, 2006. © 2005 Society of Plastics Engineers

Rheology and curing characteristics of epoxy–clay nanocomposites

AbstractDiglycidyl ethers of bisphenol‐A (DGEBA) epoxy resin, filled separately with organoclay (OC) and unmodified clay (UC), were synthesized at room temperature and at high temperature (80 °C) by mechanical shear mixing. The room temperature curing (RTC) and high temperature curing (HTC) were carried out with the addition of triethylene tetramine (TETA) and diaminodiphenylmethane (DDM) curing agents respectively. The OC used was alkyl ammonium modified montmorillonite (MMT) and the UC was Na+‐MMT. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study the structure and morphology of the nanocomposites. The influence of OC and UC particles on rheology and curing characteristics was studied. The rate of increase in viscosity was higher for OC‐filled resin than that of the UC‐filled resin. The curing study showed that the amine ions of the OC aided the polymerization process and favoured the curing at low temperature over the curing of unfilled epoxy resin. The tensile properties were enhanced for epoxy filled with OC particles rather than those filled with UC particles. Copyright © 2005 Society of Chemical Industry

Fracture toughness and water uptake of high-performance epoxy/nanoclay nanocomposites

Aircraft grade epoxy–clay nanocomposites based on tetraglycidyl-4, 4′-diaminodiphenylmethane (TGDDM) cured with diaminodiphenyl sulphone (DDS) were synthesized. Nanoclay was dispersed in both acetone and an acetone epoxy solution with a high pressure mixing (HPM) method to form pastes. The basal spacing of the nanoclay in these pastes was increased as observed from X-ray diffraction (XRD) data. Transmission electron microscopy (TEM) images show that the agglomerates of nanoclay were broken down to form small particles consisting of several clay platelets. Fracture toughness of this epoxy system has been greatly enhanced with the addition of nanoclay. With the addition of only 4.5 phr of clay, the strain energy release rate of the epoxy is increased 5.8 times from the original value. Scanning electron microscope (SEM) was used to examine the characteristics of the fracture surfaces from the different materials. There is also significant reduction in the diffusivity and the maximum water uptake of the epoxy resin with the addition of the nanoclay.

Thermal and combustion behaviour of layered silicate–epoxy nanocomposites

The present research looks at the thermal properties of epoxy–clay nanocomposites synthesised by in situ polymerisation of a prepolymer (diglycidyl ether of bisphenol-A) crosslinked with methyl tetrahydrophthalic anhydride. The inorganic phase was montmorillonite, exchanged with alkylammonium ions in order to give organophilic properties to the phyllosilicate. The morphology of epoxy–montmorillonite nanocomposites examined by X-ray diffraction and transmission electron microscopy shows that mixed delamination or intercalation or microdispersion can occur depending on type of organoclay. Thermogravimetric analysis shows that in nanocomposites the epoxy matrix is sheltered from the action of oxygen. Cone calorimeter tests show that the rate of heat release in the nanocomposite combustion is strongly reduced.

Room temperature processing of epoxy-clay nanocomposites

Polymer/Clay nanocomposites consisting of an epoxy matrix filled with nanolayered silicate clay particles have been investigated. Recent and ongoing research has shown that dramatic enhancements can be achieved in mechanical and thermal properties by adding a small volume percent of clays. In the present work nanocomposites are processed by mechanical mixing of epoxy with organoclays and unmodified clays using a high speed electric shear mixer at room temperature. The addition of different organoclay wt% [1–3, 5 and 10] indicates good enhancement in hardness, dynamic mechanical properties, and also the molecular mobility of the polymer is reduced by the presence of the silicate layers, which in turn causes large stiffness improvements. X-ray diffraction (XRD) results show the intercalation/exfoliation of clays in the epoxy matrix. The influence of organoclay restricts the weight loss at varying temperatures. Experiments show improved elastic modulus for both modified and unmodified clays.

Layered silicate/epoxy nanocomposites: synthesis, characterization and properties

AbstractNovel epoxy‐clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T‐403), primary polyethertriamine (Jeffamine T‐5000) and three types of polyoxypropylene diamine (Jeffamine D‐230, D‐400, D‐2000) with different molecular weight were used to treat Na‐montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na+ in MMT with the organic ammonium group in Jeffamine compounds. X‐ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine‐MMT intercalates. Jeffamine D‐230 was used as a swelling agent for the organoclay and curing agent. It was established that the d001 spacing of MMT in epoxy‐clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000‐MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5 nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140 nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three‐fold increase in the energy required for breaking the test specimen was found for T5000‐MMT/epoxy containing 7 wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd.

S2-Glass/Epoxy Polymer Nanocomposites: Manufacturing, Structures, Thermal and Mechanical Properties

This paper is primarily focused in studying the effects of nanoclay particles such as montmorillonite on improving mechanical and thermal properties of fiber reinforced polymer matrix composite materials. Basic correlations between polymer morphology, strength, modulus, toughness, and thermal stability of thermoset nanocomposites were investigated as a function of layered silicate content. S2-glass/epoxy-clay nanocomposites were manufactured through an affordable vacuum assisted resin infusion method (VARIM). The nanocomposites are formed during polymerization when the adsorbing monomer separates the clay particles into nanometer scales. Transmission electron microscopy (TEM) and wide angle X-ray diffraction(WAXD) were used to characterize the morphology of the dispersed clay particles. The thermal properties such as onset of decomposition and glass transition temperatures were determined by Thermo Gravimetric Analysis (TGA) and Dynamic Modulus Analyzer (DMA). Mechanical properties such as interlaminar shear strength, flexural properties and fracture toughness are also determined for both conventional S2-glass/epoxy composites and S2-glass fiber reinforced nanocomposites. The results show significant improvements in mechanical and thermal properties of conventional fiber reinforced composites with low loading of organo silicate nanoparticles. By dispersing 1% by weight nanosilicates, S2-glass/epoxy-clay nanocomposites attributed to almost 44, 24 and 23% improvement in interlaminar shear strength, flexural strength and fracture toughness in comparison to conventional S2-glass/epoxy composites. Similarly, the nanocomposites exhibit approximately 26 C higher decomposition temperatures than that of conventional composites. This improved properties of fiber reinforced polymer nanocomposites are achieved mostly due to increased interfacial surface areas, improved bond characteristics and intercalated/exfoliated morphology of the epoxy-clay nanocomposites. The TEM observations provide evidence of detailed morphology of the polymer layered-clay nanocomposites.

Study of the exfoliation process of epoxy-clay nanocomposites by different curing agents

Epoxy–clay nanocomposites were synthesized using two organoclays cured with different chemicals at different temperatures. Interlayer distance of the clay layers and curing process were investigated by X-ray diffraction and infrared spectra. The clay treated with facilitated curing agent, 2,4,6-tris[(dimethylamino)methyl]phenol, can exfoliate at all curing conditions, but for the other clay treated with low-speed curing agent, p,p′-diaminodiphenylmethane, exfoliation of the clay layers does not occur. It was found that the relative curing speed between the interlayer and extralayer was the most important factor determining clay exfoliation. Exfoliated epoxy–clay nanocomposites can be prepared if the curing speed of the interlayer is higher than that of the extralayer, irrespective of the curing agent and temperature used. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 511–517, 2003