Sustainable synthetic strategy for preparing high-loaded clay-rubber nanocomposites

Global industry is showing a great interest in the field of sustainability owing to the increased attention for ecological safety and utilization of renewable materials. For the scientific community, the challenge lies in the identification of greener synthetic approaches for reducing the environmental impact. In this context, we propose the preparation of novel nanocomposites (NCs) consisting of natural rubber latex (NRL) and sepiolite (Sep) fibers through the latex compounding technique (LCT), an ecofriendly approach where the filler is directly mixed with a stable elastomer colloid (1). This strategy favors a homogeneous dispersion of hydrophilic Sep fibers in the rubber matrix, allowing the production of high-loaded sepiolite/natural rubber (Sep/NR) NCs) without the use of surfactants. This process is more sustainable than melt mixing, in which the incorporation of very large amounts of filler requires significant energy input and may lead to the release of powder in the working environment, rising problems of compounding, dispersibility and contamination. The main physicochemical parameters which control aggregation processes in the aqueous medium, i.e., pH, ?-potential, size and shape of colloidal systems, and the morphological features of the final NCs were comprehensively investigated in order to figure out the interactions among Sep fibers and NR, and to propose a flocculation mechanism characteristic of each Sep/NR system. Finally, the mechanical properties of NR/Sep NCs obtained by LCT were determined by strain sweep analysis and compared to those of analogues NCs prepared by conventional melt blending