Clay tensile yield stress

Sumita M, Tsukumo Y, Miyasaka K et al (1983) Tensile yield stress of polypropylene composites filled with ultrafine particles. J Mater Sci 18 1758—1764 Thellen C, Orroth C, Froio D et al (2005) Influence of montmorillonite layered silicate on plasticized poly(l-lactide) blown films. Polymer 46 1716-11727 Uyama H, Kuwabara M, Tsujimoto T et al (2003) Green nanocomposites from renewable resources plant oil-clay hybrid materials. Chem Mater 15 2492-2494 Wang SF, Shen L, Zhang WD et al (2005a) Preparation and mechanical properties of chitosan/ carhon nanotuhes composites. Biomactomolecules 6 3067—3072... 

Table 5.1 Elastic modulus and tensile yield stress of several clay-thermoplastic...

Matrix Clay content (wt%) Elastic modulus (CPa) Tensile yield stress (MPa)... 

The procedure to obtain nanocomposites based on unsaturated polyester resins leads to improvements in the order of 120% in the flexural modulus, 14% in flexural strength and 57% increase in tensile modulus with 4.7% of clay slurry content. Thermal stability augments and the gelation temperature increases to 45 °C, as compared to that of the resin (Fig. 31.6). It seems that adding water to the MMT allows better intercalation of polymer chains into the interlamellar space. Because clay is first suspended in water, this improves dispersion and distribution of the particles in the resin matrix. Longer gelation times lead to more uniform and mechanically stronger structures and to yield stresses (Fig. 31.7). Enhanced polymer-clay interactions are revealed by XPS in this case (Fig. 31.8). 

Recently, a big window of opportunities has opened for polymer nanocomposites just to overcome the limitations of traditional microcomposites. Although, the chemistry of clay minerals and composites based on some nanoscale particles is known for several decades, the research and development of nanoscale-filled polymers has been skyrocketed in recent years, for numerous reasons. First, unprecedented combinations of properties have been observed in some polymer nanocomposites. For example, incorporation of isodimensional nanoparticles into thermoplastics increases the modulus, the yield stress, and the ultimate tensile strength (Sumita et al. 1983). 

The clay platelets (Cloisite 30B) are assumed to be elastic and isotropic with tensile modulus E=200 GPa and Poisson ratio v= 0.2 [22]. The epoxy system (DGEBA epoxy base + amminic hardener) is modelled by a nonlinear Ramberg-Osgood (RO) law whose parameters are obtained by fitting to available experimental results - Young s modulus E=3230 MPa, Poisson s ratio v= 0.34, yield stress osn = 30 MPa, and two additional coefficients n= 4.5, a= 0.0767. 

Fig. 37 Stress-strain curves for M-NCs with different clay contents (M-NC5.5-M-NC23) and for chemically crosslinked M-OR3. /, //, and HI indicate the distinct stages of tensile deformation. A stress-strain curve for the second cycle of M-NCl 1 after the first elongation up to 1,800% is also shown as a dotted line. Inset. Example of yielding behavior observed for M-NCll with two necking points, which start at both ends where a high stress concentration initially occurred at the grips. Reprinted from Haraguchi et al. [31], Copyright 2006, with permission of Wiley...

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