Effect of temperature, duration and speed of pre-mixing on the dispersion of clay/epoxy nanocomposites (original) (raw)
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Polymer Engineering & Science, 2009
The effect of the dispersion and intercalation/exfoliation of organoclay on the mechanical properties of epoxy nanocomposites was studied. The epoxy resin was EPON™ 828 and the hardener was an amine-terminated polyoxypropylene diol, namely Jeffamine ® D-230. 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 epoxy resin and its nanocomposites were cured at 120°C for 2 hours, with subsequent post cure at 140°C for 2 hours. 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 the strength is very sensitive to the dispersion and only good dispersion can improve the strength, while poor dispersion results in loss of strength. Unlike the modulus, 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.
Effect of Shearing on Dispersion , Intercalation / Exfoliation of Clay in Epoxy
2007
Nanocomposites from Shell EPON828 and Jeffamine D230 (D230) were prepared by different mixing methods which can generate different shear forces such as mechanical stirrer, microfluidizer and homogenizer. An organoclay Cloisite 30B (montmorillonite treated with a quaternary ammonium intercalant) was used. The quality of dispersion and intercalation/exfoliation was analyzed by XRD, FEGSEM and TEM. The tensile and compressive properties of the epoxy and epoxy nanocomposites (ENC) were also determined.The result indicates that well dispersed and well intercalated/exfoliated ENC is achieved with a non solvent assistance method. It is also found that with finer and more uniform dispersion of the clay in ENC achieved by this solvent free method the tensile strength is improved.
Composites Science and Technology, 2011
This paper investigates the effect of both the mixing technique and heating rate during cure on the dispersion of montmorillonite (MMT) clay in an epoxy resin. The combination of sonication and using a 10 °C/min heating rate during cure was found to facilitate the dispersion of nanoclay in epoxy resin. These processing conditions provided a synergistic effect, making it possible for polymer chains to penetrate in-between clay galleries and detach platelets from their agglomerates. As the degree of dispersion was enhanced, the flexural modulus and strength properties were found to decrease by 15% and 40%, respectively. This is thought to be due to individual platelets fracturing in the nanocomposite. Complementary techniques including X-ray diffraction (XRD), small angle X-ray scattering (SAXS), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX), transmission electron microscopy (TEM) and optical microscopy were essential to fully characterise localised and spatial regions of the clay morphologies.► Effect of mixing method and heating rate on dispersion of MMT in epoxy investigated. ► Sonication and a 10 °C/min heating rate facilitated the dispersion of MMT in epoxy. ► As the degree of dispersion was enhanced, the flexural properties decreased. ► XRD, SAXS, SEM–EDX, TEM and optical microscopy fully characterised clay morphologies.
New method for the synthesis of clay/epoxy nanocomposites
Journal of Applied Polymer Science, 2006
A new liquid-liquid method for the synthesis of epoxy nanocomposites was developed. This new method improved the dispersion and exfoliation of the organoclay in the polymer matrix, thus improving the end-use properties. The microstructure and physical properties of the clay/epoxy nanocomposite synthesized by the new method were studied. Rheological tests of the uncured epoxy-organoclay system demonstrated that this method resulted in a great increase in viscosity, much more than the most commonly used direct-mixing method. The Krieger-Dougherty model successfully described the dispersion of the clay layers in the uncured epoxy. In the 5 wt % organoclay nanocomposite, compressive tests on the cured samples showed that there was a 45% increase in the maximum strength, a 10% increase in the yield strength, and a 26% increase in the modulus over the pure epoxy-amine cured system.
Journal of University of Anbar for Pure Science
In the previous few decades, nanocomposites including epoxy risen-clay nanoparticles systems were proven possibility to have developed properties over original matrices. The environmental conditions, which surround the nanocomposite systems, have a scientific effect on their properties during using them for a long time. Therefore, studying the effect of environmental conditions associated with adding clay nanoparticles on the properties of nanocomposites is important to achieve the requirement of the applications. Nanocomposites are utilized in substructure applications and experience mechanical loads and thermal effects when they are exposed to environmental surrounding conditions which are included electromagnetic ultraviolet (UV) energy, humidity or wetness, water absorbance, and some alkaline solutions. These materials are showed their ability to barrier the environmental surrounding effects. Diffuse the liquids in nanocomposite systems has been established by different approaches (models). The review study involves the research effort performed on nanocomposite (epoxy-clay nanoparticles) under some environmental issues such as moisture or water properties and their diffusion into nanocomposite, exposure to various environments: radiation in the range of UV, temperature, and humidity. The current developments are additionally discussed.
Processing of clay/epoxy nanocomposites by shear mixing
Scripta Materialia, 2003
A three-roll mill was used to disperse/exfoliate the clay nanoparticles in an epoxy matrix. The compounding process was carried out with varying clay contents (1-10 wt.%). The technique was found highly efficient and environmentally friendly in achieving high levels of exfoliation and dispersion within a short period of time.
Polymer Engineering & Science, 2006
montmorillonite clay nanoplatelets were investigated using anhydride-and amine-curing agents. The sonication technique was used to process epoxy/clay nanocomposites. The basal spacing of clay nanoplatelets was observed by wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS) techniques, and transmission electron microscopy. It was found that the basal spacing of clay nanoplatelets in epoxy matrix was expanded after mixing with either DGEBA/DGEBF or methyltetrahydrophthalic-anhydride (MTHPA) curing agent. The sonication technique provided larger d-spacing of clay nanoplatelets. Because of the different curing temperatures, MTHPA-cured epoxy/clay nanocomposites produced more expanded d-spacing of clay nanoplatelets modified with methyl, tallow, bis(2-hydroxyethyl) quaternary ammonium (MT2EtOH) than triethylenetetraminecured nanocomposites. Depending on the selection of curing agent and organic modification for clay nanoplatelets, the d-spacing was expanded to be up to 8.72 nm. POLYM.
Materials, 2013
The role of processing conditions and intercalant chemistry in montmorillonite clays on the dispersion, morphology and mechanical properties of two epoxy/clay nanocomposite systems was investigated in this paper. This work highlights the importance of employing complementary techniques (X-ray diffraction, small angle X-ray scattering, optical microscopy and transmission electron microscopy) to correlate nanomorphology to macroscale properties. Materials were prepared using an out of autoclave manufacturing process equipped to generate rapid heating rates and mechanical vibration. The results suggested that the quaternary ammonium surfactant on C30B clay reacted with the epoxy during cure, while the primary ammonium surfactant (I.30E) catalysed the polymerisation reaction. These effects led to important differences in nanocomposite clay morphologies. The use of mechanical vibration at 4 Hz prior to matrix gelation was found to facilitate clay dispersion and to reduce the area fraction of I.30E clay agglomerates in addition to increasing flexural strength by over 40%.
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.