Superior reinforcement of ethyl-co-vinyl acetate rubber composites by using nano-sized starch filler: The role of particle size and reactive compatibilization

Nano-sized starch (NSt) was reported as reactive filler to reinforce ethylene-co-vinyl acetate rubber (EVM) by using epoxy-functionalized EVM (GMA-EVM) as compatibilizer together with 3-(2-aminoethylamino) propyl dimethoxy methyl silane (KH602). This resulted in EVM/GMA-EVM/NSt nanocomposites having significant improved properties. The improvement is attributed to the small starch particle size and chemical compatibilization. The tensile strength (Ts) was increased from 9.2 to 18.7 MPa when 20 phr (per hundred rubber by weight) of the GMA-EVM compatibilizer is incorporated. Compared to EVM/NSt, the EVM/GMA-EVM/NSt nanocomposites possess stronger interfacial interaction between fillers and the matrix according to morphology and crosslink density analysis. Besides the crosslink of EVM and GMA-EVM chains created by dicumyl peroxide (DCP), under the aid of KH602, extra chemical bonding was generated between: (a) GMA-EVM chains, (b) GMAEVM and NSt. Thus, strong reinforcement of EVM was obtained. These interesting results provide a new insight to make robust rubbers which may create new applications for rubbers and natural fillers.