# A Green Approach for Preparing High-Loaded Sepiolite/Polymer Biocomposites
## 4 Conclusions  
SepX/NR biocomposites were prepared by a novel green LCT approach, consisting of blending an aqueous colloidal suspension of SepX fibers in a NRL suspension, resulting in a fast flocculation process, without using any synthetic flocculation agent. The proposed method promotes a homogeneous dispersion of low hydrophilic Sep fibers in the rubber matrix, allowing the production of high-loaded Sep rubber composites. TEM investigation performed at the early stages of mixing revealed that, when SepB5 fibers bearing alkylammonium salt functionalities are utilized, homo-aggregated NRL micelles embedding some SepB5 fibers are detectable while, in Sep9/NR colloidal system, Sep bundles lay among or in the periphery of the rubber micelles, thus suggesting their poor interactions with NRL. The same survey performed on the final biocomposite, revealed for SepB5/NR the presence of large and compact filler domains constituted by self-assembled and aligned Sep fibers interconnected by rubber. Conversely, for SepS9/NR poorly tight filler aggregates were detected in the biocomposite, indicating the occurrence of weak interactions between the organic and inorganic components. SAXS analysis supported these outcomes pointing out that, in NR colloidal system, the polymer chains, once in contact with the SepS9 fibers, unfold leading to the formation of a homogeneous material. These results allowed us to propose a flocculation mechanism characteristic for both SepB5/NR and SepS9/NRL systems, based on electrostatic and depletion attraction forces, respectively, and remarkably connected both to the high content (50 wt. %) and to the peculiar anisotropy of Sep fibers. Finally, the uniform Sep distribution in the rubber matrix, characteristic of the proposed LCT approach, and the percolative filler network formed give rise to enhanced mechanical properties for SepX/NR biocomposites in comparison to those of analogous materials prepared by conventional melt blending technique. Although this work focuses on Sep/NR nanocomposites, we expect that the developed sustainable synthetic strategy may be potentially extended to the production of high-loaded clay-rubber nanocomposites. The following are available online at [[http://www.mdpi.com/2079-4991/9/14/6/s1](http://www.mdpi.com/2079-4991/9/14/6/s1)]([http://www.mdpi.com/2079-4991/9/14/6/s1](http://www.mdpi.com/2079-4991/9/14/6/s1)), Figure S1: DLS (dynamic light scattering) analysis of NRL (natural rubber latex), Figure S2: SEM micrographs of (a) SepS9 and (b), Figure S3: \(\zeta\)-Potential of SepS9 after 20 min, 40 min, 3 h and 24 h of mixing SepB5, Figure S4: The weight percent of ammonium ions physi/chemisorbed onto SepS9, Table S1: Mg\({}^{2+}\) amount released at different time of mixing of SepS9, Figure S5: TGA (thermogavirimetric analysis) curves recorded under air flux of: (a) NR (continuous black line), SepS9(grey dot line), SepS9/NR biocomposite (orange dashed line); and (b) NR (continuous black line), SepB5 (grey dot line), SepB5/NR biocomposite (blue dashed line), Figure S6: XRD (X-ray Diffraction) patterns of (a) SepS9 (black line) and the corresponding SepS9/NR biocomposite (orangeline), and of (b) SepB5 (black line) and the corresponding SepB5/NR biocomposite (blue line), Figure S7: SEM (scanning electron microscopy) micrographs of (a) SepS9/NR biocomposite and (b) SepB5/NR biocomposite and the corresponding silicon-mapping performed by EDS on (a') SepS9/NR biocomposite and (b') SepB5/NR biocomposite, Figure S8:Guinier plot (circle lines) and liner fit (red line) of (a) SepS9 and (b) SepB5, Table S2. Parameters of the Guinier analysis of the SAXS curves of SepX. [PERSON] supervised the project and prepared the manuscript; [PERSON] performed the characterization of colloidal dispersions, the preparation of the SepX/NR biocomposites and most of morphological, spectroscopic and mechanical characterizations; [PERSON] performed thermal and spectroscopic characterization; [PERSON] and PS.