Viscoelastic response of nanocomposite poly(vinyl acetate)‐hydroxyapatite with varying particle shape—Dynamic strain softening and modulus recovery

Abstract Dynamic‐strain softening known as the Payne effect was investigated in the case of poly(vinyl acetate)‐hydroxyapatite (PVAc‐HA) model nanocomposites in which the nanoparticles served as reversible physical cross‐links. HA nanofillers with different particle shape and with size ranging from 5 to 60 nm were used. Filler concentration in PVAc nanocomposites was limited to maximum of 5 vol%. Dynamic‐mechanical spectra were recorded as a function of structural variables, strain amplitude, and test temperature using the dynamic‐mechanical thermal spectroscopy (DMTS). Additionally, amplitude sweep tests were supplemented by the modulus recovery experiments to provide relaxation time data. Observed phenomena were interpreted using polymer physics approach. POLYM. COMPOS., 28:743–747, 2007. © 2007 Society of Plastics Engineers