# A Green Approach for Preparing High-Loaded Sepiolite/Polymer Biocomposites
## 3 Results and Discussion
### Dynamic-Mechanical Properties of SepX/NR Biocomposites  
The dynamic-mechanical behaviour of SepX/NR biocomposites was compared to REF-SepX/NR composite, with the same filler content and obtained by conventional blending technique.  
Strain sweep is a standard technique to quantify the contributions of the so-called \"filler network\" in composite materials formed by a percolating solid phase of filler particles embedded in a polymer matrix. Thus, in order to compare the behaviour of the filler network under large deformations or in the nonlinear region, strain sweep measurements at 80 \({}^{\circ}\)C were performed. The results of these measurements are shown in Figure 7 in terms of storage (G') and loss moduli (G\"), for both fillers SepS9 (Figure 7a) and SepB5 (Figure 7b).  
In all uncured samples, results from shear measurements with strain amplitude increasing from 0.01 to 60% show a decrease of the storage modulus G'. This decrease in elastic modulus upon increasing the strain amplitude, i.e., Payne effect, is commonly related to the filler-filler interaction which are broken under strain. The short-distance forces between filler particles decrease strongly from low strain to high strain values. The breakdown of the filler network by increasing strain amplitude would also release the occluded rubber so that the effective filler volume fraction and hence the modulus decrease. For this reason, the Payne effect is used as a measure of filler networking originating from filler-filler interactions as well as from filler-polymer interactions, particularly for silicate-loaded rubber compounds.  
In detail, the strain sweep curves obtained for SepS9/NR and REF-Sep9/NR samples are almost superimposable (Figure 7a) with the same G' values both at low and high strain, advising that filler-filler and filler-rubber interactions are not affected by the mixing approach utilized.  
G' for SepB5/NR (Figure 7b) shows a significant but less pronounced sigmoidal decrease compared to REF-SepB5/NR and, consequently, a lower Payne effect. This suggests the formation of a  
Figure 7: Storage modulus G’ (storage modulus, plain circle lines) and loss modulus G” (loss modulus, empty circle lines) vs strain for (**a**) NR/SepS9 biocomposite (orange lines), REF-SepS9/NR (Reference-Sepiolite S9/Natural Rubber) nanocomposite (black lines) and for (**b**) NR/SepB5 biocomposite (blue lines), REF-SepB5/NR (black lines).  
more compact filler network in the biocomposite rather than in the blended one possibly due to better filler-rubber interactions [55].  
In general, the low Payne effect observed for SepX/NR represents an indication of fast recovery of the filler network after a single large-amplitude deformation. As shown in TEM images, this may be related to the peculiar self-assembly and alignment of Sep fibers which improve their interfacial interaction with rubber.  
G\({}^{\prime\prime}\) of nanocomposites is commonly related to the energy dissipation during deformation, which is associated with the breakage and rebuilding of filler-filler network and slippage of the polymer chains. Thus G\({}^{\prime\prime}\), known also as viscous modulus, describes the viscous behaviour of a nanocomposite. In the present case, the energy dissipation processes are quite similar for both SepX/NR and the related reference materials.  
Similar to the storage modulus, G\({}^{\prime\prime}\) decreased at high strain amplitudes. However, biocomposites enclosing SepX fibers show only a moderate decay of G\({}^{\prime\prime}\). This effect may be attributed to the aforementioned Sep rubber interactions, which hinder the slippage of the macromolecular chains.  
In addition, the maximum peak in G\({}^{\prime\prime}\) curves is slightly broaden and shifted to the higher strain amplitude for SepX/NR biocomposites in comparison with reference materials, indicating an improvement of the filler network stability during the strain sweep [56].