Epoxy Nanocomposites with Highly Exfoliated Clay: Mechanical Properties and Fracture Mechanisms (original) (raw)
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Journal of Nanomaterials, 2014
The effects of organic modifier and processing method on morphology and mechanical properties of epoxy-clay nanocomposites were investigated. In this study, the preparation of nanocomposites by exfoliation-adsorption method involved an ultrasonic mixing procedure, and mechanical blending was used for in situ intercalative polymerization. The microstructure study revealed that the organoclay, which was ultrasonically mixed with the epoxy, partially exfoliated and intercalated. In contrast, organoclay remained in phase-separated and flocculated state after the mechanical blending process. Tensile stiffness increased significantly for the nanocomposite prepared by ultrasonic dispersion method through realizing the reinforcing potential of exfoliated silicate layers. Nanocomposites with exfoliated and intercalated nanoclay morphology were ineffective in enhancing the fracture toughness whereas nanocomposites with phase-separated and flocculated morphology have improved crack resistance predominantly by crack deflecting and pinning mechanisms.
Preparation and Properties of Clay-Reinforced Epoxy Nanocomposites
International Journal of Polymer Science, 2013
The clay-reinforced epoxy nanocomposite was prepared by the polymerization method. The effect of clay addition on the mechanical properties of epoxy/clay nanocomposites was studied through tensile, flexural, impact strength, and fracture toughness tests. The morphology and tribology behavior of epoxy/clay nanocomposites were determined by X-ray diffraction (XRD) and wear test, respectively. The wear test was performed to determine the specific abrasion of the nanocomposites. In addition, the water absorption characteristic of the nanocomposites was also investigated in this study. XRD analysis indicated that the exfoliation structure was observed in the epoxy nanocomposites with 3 wt% of clay, while the intercalated structure was shown at 6 wt% of clay. It was found that the addition of clay up to 3 wt% increased the tensile strength, flexural strength, impact strength, and the fracture toughness. On the contrary, the presence of above 3 wt% of clay produced a reverse effect. It cou...
Mechanical Properties of Epoxy Clay Nanocomposites
Achievement of exfoliated structure of polymer/ Clay nanocomposites is of particular interest for the improvement of mechanical properties. In this work, the morphology and mechanical properties of epoxy/ clay nanocomposites has been investigated. Diglycidyl ether of bisphenol A (DGEBA) epoxy resin (EPON828) and Jeffamine D400 curing agent was used. To obtain perfect dispersion, nanoclay (Cloisite 30B) was sonicated in acetone. The mixture was then mixed with polymer. Afterwards, the curing process was performed by addition of curing agent and degassing. Disappearing of peaks in X-Ray diffraction patterns of nanocomposites containing less than 5wt% nanoclay, is a good evidence of perfect dispersion of layered silicates in matrix, i.e. formation of exfoliated morphology. Based on tensile test results, it is deduced that as the amount of nanoclay increases, the elastic modulus and elongation at break of the nanocomposites containing 1wt% and 5wt% nanoclay increases by 12% and 31%, respectively. Therefore, obtaining perfect dispersion of layered silicates in epoxy matrix and exfoliated morphology, results in better mechanical properties of the nanocomposites.
2014
Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF 3 •MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF 3 •MEA into the clay galleries of nanocomposites containing 2 wt% MMT.
Composites Science and Technology, 2013
A computational model of a 3D representative volume element (RVE) for epoxy/clay nanocomposites is introduced to study their constitutive relationship and damage mechanisms. The model is composed of an epoxy matrix with embedded silicate layers. A gallery inter-layer is inserted between the silicate layers to mimic actual epoxy/clay nanocomposites. The predicted constitutive relationship and damage patterns of the epoxy/clay model with 3% weight fraction of nanoclay were in good agreement with experimental data and observation. It was found that some parameters of the clay particles such as the particle size and the number of silicate layers do not always affect the elastic stiffness or tensile strength of epoxy/clay nanocomposites. The model showed that when the gallery strength is larger than half that of the matrix, only matrix damage occurs. When the gallery strength decreases below this critical value, the tensile strength for the nanocomposites would decrease accordingly. This effect could possibly explain why experimental data for the tensile strength of epoxy/clay nanocomposites shows a large variation. By including an interphase layer between the epoxy matrix and clay particles, it was observed that the strength and damage patterns of the nanocomposites can change considerably with changes in the relative strength of the gallery and the interphase.
Materials Science and Engineering: A, 2007
In this study, the effect of montmorillonite (MMT) clay modification and concentration on the tensile behavior of MMT/epoxy nanocomposite was investigated. MMT was surface-modified using 3-aminopropyltriethoxysilane. MMT/epoxy nanocomposite samples were fabricated by mixing the unmodified and the surface-modified MMT of 2, 6, and 10 wt%, respectively, with epoxy resin. XRD analysis was performed to determine the increase of spacing between layers, after the modification. Tensile tests were performed on the MMT/epoxy nanocomposite specimens with and without the MMT modification. The results showed that the d-spacing between layers increased by more than 55% with the 3-aminopropyltriethoxysilane modification of MMT. For unmodified MMT/epoxy nanocomposite, as the concentration of clay increased the elastic modulus increased, but the tensile strength was not affected significantly. For surface-modified MMT/epoxy nanocomposite, both the elastic modulus and the tensile strength increased as the concentration of clay increased. Tensile strength and elastic modulus of surface-modified MMT/epoxy nanocomposite were larger than those of unmodified MMT/epoxy nanocomposite, and the modification effect increased with clay concentration. This occurred due to the increased exfoliation of clays along with the improved interfacial strength by the surface modification.
Overall Effect Of Nano Clay On The Physical Mechanical Properties Of Epoxy Resin
2011
In this paper, the effect of modified clay on the mechanical efficiency of epoxy resin is examined. Studies by X ray diffraction and microscopic transient electron method show that modified clay distribution in polymer area is intercalated kind. Examination the results of mechanical tests shows that existence of modified clay in epoxy area increases pressure yield strength, tension module and nano composite fracture toughness in relate of pure epoxy. By microscopic examinations it is recognized too that the action of toughness growth of this kind of nano composite is due to crack deflection, formation of new surfaces and fracture of clay piles.
Environmental Degradation and Durability of Epoxy-Clay Nanocomposites
Journal of Nanomaterials, 2010
This experimental investigation reports on the durability of epoxy-clay nanocomposites upon exposure to multiple environments. Nanocomposites are fabricated by mixing the clay particles using various combinations of mechanical mixing, high-shear dispersion, and ultrasonication. Clay morphology is characterized using X-ray diffraction and transmission electron microscopy. Specimens of both neat epoxy and the epoxy-clay nanocomposite are subjected to two environmental conditions: combined UV radiation and condensation on 3-hour repeat cycle and constant temperature-humidity, for a total exposure duration of 4770 hours. The presence of nanoscale clay inhibits moisture uptake, as demonstrated by exposure to constant temperature-humidity. Nonetheless, both materials lose mass under exposure to combined UV radiation and condensation due to the erosion of epoxy by a synergistic process. Surprisingly, the epoxy-clay specimens exhibit greater mass loss, as compared to neat epoxy. Mechanical testing shows that either environment does not significant affect the flexure modulus of either material. On the other hand, both materials undergo degradation in flexural strength when exposed to either environment. However, the epoxy-clay nanocomposite retains 37% more flexure strength than the neat epoxy after 4072 hours of exposure.
Polymer Engineering and Science, 2011
The effect of the dispersion and intercalation/exfoliation of organoclay on the mechanical properties of epoxy nanocomposites was studied. The epoxy resin was EPON828 and the hardener was Jeffamine D-230, an amine-terminated polyoxypropylene diol. The organoclay Cloisite 30B (montmorillonite treated with a quaternary ammonium intercalant) was used. Nanocomposites were prepared by different mixing devices that can generate different shear forces, such as a mechanical stirrer, a microfluidizer, and a homogenizer. The tensile and compressive properties of the epoxy resin and its epoxy nanocomposites (ENCs) were determined. The effects of nanoclay on the mechanical properties of the EPON828-D230 system were also investigated by dynamic mechanic analysis (DMA). The results indicate that the modulus increases almost linearly with the clay loading and also is improved with the quality of micro-dispersion, although the latter plays a less important role. On the other hand only good dispersion can improve the strength, while poor dispersion results in loss of strength. The strength levels off above 4 wt% organoclay loading. It can be concluded that finer and more uniform dispersion increases the clay surface area available for interaction with the matrix and reduces stress concentration in the large aggregates that initiate the failure under stress. It is also observed that the presence of nanoclay C30B does not significantly affect the T g of the epoxy systems regardless of the level of clay dispersion and clay loading. DMA results also show the positive effect of dispersion and intercalation/exfoliation on the storage modulus of ENCs.
Clay-Epoxy Nanocomposites: Processing and Properties
JOM Journal of the Minerals, Metals and …, 2007
The work described in this paper is focused on evaluating the effect of the processing method and nanoclay (montmorillonite) content on the ten-sile, compressive, and impact proper-ties of clay-epoxy nanocomposites. Nanocomposites are synthesized by two methods: ...