Clay elastic modulus

Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

Mapping of the elastic modulus of the glassy and rubbery blocks and clay regions was probed by employing Hertzian and Johnson-Kendall-Roberts (JKR) models from both approaching and retracting parts of the force-distance curves. In order to determine the elastic properties of SEBS nanocomposites in its different constituting zones, the corrected force-distance curve was fitted to the Hertz model ... 

Hbaieb et al. [260] recently suggested that Mori-Tanaka and 2D FEM models do not predict accurately the elastic modulus of real clay/PNCs. The Mori-Tanaka model underestimates the stiffness at higher volume fractions (>5%) and overestimates the stiffness of exfoliated clay/PNCs. 

The subgrade used in the analysis was assumed to be a clay material (A-6 classification) with a moisture content of about 23% and an elastic modulus of 15,000 psi. The base course used in the analysis was assumed to be a dense graded crushed aggregate with an elastic modulus of 60,000 psi. These two materials were assumed to be elastic and are typical of those used in construction of many pavements throughout the U.S. 

Le Pluart et al. (2004) and Becker et al. (2003a) showed the effects of nanoclays on dynamic rheology and steady viscosity prior to cure and post-cure. There was a clear increase in low-frequency elastic modulus and low shear viscosity before cure, and a clear increase in fully cured mechanical properties post-cure with increasing clay content. 

At the same time, elasticity may also have completely different, i.e. entropic, nature. For instance, the applied stress causes segments of macromolecules in polymers, or lamellar particles present in clay suspensions to co-orient in a way that leads to a decrease in entropy. In this case the tendency of an object to restore its original configuration is related to thermal motion, which distorts the acquired co-orientation. Under these conditions elasticity modulus (the entropic elasticity modulus) is small and to a significant extent depends on temperature. 

Another interesting observation [61] is that remarkable increases in the elastic modulus at low frequency with low values of the molecular weight reflect the fact that an elastic network is formed due to the presence of the clays. 

Mondragon et al. [250] used unmodified and modified natural mbber latex (uNRL and mNRL) to prepare thermoplastic starch/natural rubber/montmorillonite type clay (TPS/NR/Na+-MMT) nanocomposites by twin-screw extrusion. Transmission electron microscopy showed that clay nanoparticles were preferentially intercalated into the mbber phase. Elastic modulus and tensile strength of TPS/NR blends were dramatically improved as a result of mbber modification. Properties of blends were almost unaffected by the dispersion of the clay except for the TPS/ mNR blend loading 2 % MMT. This was attributed to the exfoliation of the MMT. 

Figure 23 Elastic modulus. C, as a function of solid concentration and pH. for suspensions of clay. (Adapted from Ref. 12)...

Diaminodecane and 1,10-decanedicarboxylic acid were polyconden-sated in the presence of an organophihc clay to polymerize a nylon 1012 clay nano composite [27]. X-ray diffraction and TEM observations revealed that the clay layers were exfoliated and uniformly dispersed in nylon 1012. The speed of crystallization of the nanocomposite increased compared with nylon 1012. Furthermore, the tensile strength and the elastic modulus in tension were improved, and the amount of absorbed water was decreased through the improvement of the barrier characteristics. 

In particular, EPR-CN8 fractured without manifesting a yield point. The elastic modulus of EPR-CN increased as the amount of clay increased. It was... 

TS = tensile strength, EM = elastic modulus (EM), EB = elongation at break) Table 3. Tensile properties of chitosan and chitosan/clay films. 

Mondragon et al ° reported that unmodified and modified NR latex were used to prepare thermoplastic starch/NR/MMT nanoeomposites by twin-screw extrusion. After drying, the nanoeomposites were injection moulded to produce test specimens. SEM of fractured samples revealed that chemical modification of NR latex enhanced the interfacial adhesion between NR and thermoplastic starch (TPS), and improved their dispersion. X-ray diffraction (XRD) showed that the nanoeomposites exhibited partially intercalated/exfoKated structures. Surprisingly, transmission electron microscopy (TEM) showed that clay nanoparticles were preferentially intercalated into the rubber phase. Elastic modulus and tensile strength of TPS/NR blends were dramatically improved from 1.5 to 43 MPa and from 0.03 to 1.5 MPa, respectively, as a result of rubber modification. 

Geological age also has an influence on the engineering behaviour of a clay deposit. In particular, the porosity, moisture content and plasticity normally decrease in value with increasing depth and thereby age, whereas the strength and elastic modulus increase. 

Shen and co-workers [91] used nano-indentation to study the effects of clay concentration on the mechanical properties, such as hardness, elastic modulus and creep behaviour of exfoliated PA 6,6-clay nanocomposites. Results were compared with those obtained by DMA and tensile tests. 

Nanoindentation tests were used by Dhaka and collaborators to study the effect of various organoclay concentrations on the nanomechanical properties of UP nanocomposites [10]. A strong correlation was found between the mechanical properties and interlayer d-spacing of clay particles in the nanocomposite system. Cured UP resins with incorporated 1%, 3%, and 5 wt% organoclay exhibited hardness increased by 29%, 24%, and 14%, respectively. Also the elastic modulus was increased by 23% with the introduction of 5 wt% organoclay. 

Using a nanoindentation technique, Shen et al. [150] studied the effects of clay concentrations on the mechanical properties (hardness, elastic modulus, and creep behavior) of exfoliated polyamide 6,6-clay nanocomposites. The results were discussed in conjnnction with those obtained by dynamic mechanical analysis and optical microscopy, and also conjunction with changes in morphology, crystallinity, and x-ray diffraction. 

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