Clays particle loading ratio

In 2007, Cao and Jana at Akron tethered Cloisite 30B clay particles onto SMP polyurethanes [70]. The polyurethanes were synthesized from aromatic diisocyanates, a crystalline polyester polyol, and poly(e-caprolactone) (PCL) diol. The monomer ratios were cleverly balanced between an excess ratio of isocyanate in the polymer system and the pendant alcohol groups (-CH2CH2OH) on the quaternary ammonium ions fi om the Cloisite 30B. The team observed an increase in the rubbery modulus at 100°C (Tm-I- 50°C) of nearly one order of magnitude, from 4—5 MPa without loading to more than 20 MPa with loading. In the carefully crafted study, the authors determined that at high (5%) clay content, a more rapid relaxation of induced tensile stress reduces the recovery force of SMPs. In addition,... 

Pluta et al. also observed an increase in thermal stability of PLA nanocomposites with the clay content by TGA, with a maximum clay loading of 5 wt.%. When further increasing the filler content, a decrease in thermal stability was observed. Such behaviour was explained by the relative extent of exfoliation/delamination as a function of the amount of OMLS. Indeed at low filler content, exfoliation dominates but the amount of exfoliated silicate layers is not sufficient to promote any significant improvement of the thermal stability. Increasing the filler content leads to relatively more exfoliated particles, and increases the thermal stability of the nanocomposites. However, when the silicate content is more than some critical value, complete exfoliation of such high aspect ratio silicate layers becomes increasingly hindered because of the geometrical constraints within the limited space available in the polymer matrix and no more increase in thermal stability or even some decrease is detected. 

Polymer nanocomposites represent a new and promising area of polymer research. Among the particles used to form nanocomposites, organically modified clays are of particular interest, hi such systems, the combination of high aspect ratio clay mono- or multilayers and their interactions with the matrix polymer can lead to improvements in barrier, thermal, and mechanical properties at far lower loading levels than are typically used in conventional filled polymer composites [1,2,3]. 

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