Design of nano-starch-reinforced ethyl-co-vinyl acetate elastomers by simultaneously constructing interfacial bonding and novel reversible matrix crosslinking

In this work, starch is demonstrated as active filler to reinforce rubber matrixes significantly with non-traditional vulcanizing agents. Nano-sized starch particles (NSt) with a diameter of ∼130 nm were prepared via reversed-phase titration. Subsequently, rubber-grade ethylene-glycidyl methacrylate-vinyl acetate/NSt (GMA-EVM/NSt) nanocomposites were prepared using ethylene diamine (EDA) and 3-(2-aminoethylamino) propyl dimethoxy methyl silane (KH602) as a cross-link agent. The tensile strength (Ts) of the KH602-cured GMA-EVM was increased from 3.0 to 17.2 MPa when 15 phr (per hunderd rubber by weight) of NSt was incorporated, while the storage modulus (e.g., at −40 °C) was increased by 50%. Moreover, the GMA-EVM/NSt nanocomposites showed a strong increasing trend in strength with higher NSt loadings. Compared to EDA, the KH602 showed stronger reinforcing effect on the GMA-EVM/NSt nanocomposites due to a fine dispersion of NSt and chemical coupling at the interface via amino-silane. In addition, the crosslink density of the GMA-EVM/NSt nanocomposites with the aid of manganese stearate decreased with time, which gives a strong indication on the potential recyclability of the cross-linked nanocomposites. A new curing option offered by GMA-EVM together with a new concept to simultaneously bond nano-starch with EVM rubber and crosslink the rubber matrix were achieved, leading to robust polymeric nanocomposites with natural fillers.