The influence of surface modification on the structure and properties of a nanosilica filled thermoplastic elastomer

Greatly dispersed nanocomposites based on a thermoplastic elastomer copolyetherester (Hytrel, Hy) matrix filled with fumed silica (SiO2) have been obtained via melt compounding varying the filler type (modified or unmodified) and filler content (up to 6 wt.%). The influence of the chemical modification was assessed by a comparison of the dispersed phase morphology and the mechanical properties of the nanocomposites. The main structural characteristics of the amorphous and crystalline phases of the pure Hy remained unchanged in the nanocomposites. Unmodified SiO2, greatly dispersed in the Hy matrix at the mixing conditions used, lead to a slight decrease in the elongation at break and to clear modulus increases (27% upon 6 wt.% SiO2 addition). Dispersion ameliorated when using silane modified SiO2 indicating a higher compatibility between the methyl groups of silane and the mainly methylenic chain of Hy, as compared to the interaction between the ester groups of Hy and the hydroxyls of silica. This modification led to even larger elongation at break values than that of Hy. The increases in the modulus of elasticity were slightly smaller than those obtained using SiO2 due to the proposed presence of a silane-induced, flexible interlayer. The creep resistance of Hy clearly improved upon SiO2 addition resulting in a reduction of the undesired, non-elastic deformation of Hy.