Synthesis, characterization, and dynamic-mechanical properties of styrene-acrylate/nanoclay interpenetrating polymer network

Waterborne styrene/acrylate latex interpenetrating polymer network (LIPN) with core-shell structure was synthesized via a three-stage emulsion polymerization method. A natural montmorillonite (MMt) and an organically modified montmorillonite (OMMt) were used to see their effect on the morphology and damping properties of polymer-clay nanocomposite LIPN. The samples were characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA), and X-ray diffraction (XRD). The appearance of a single peak in the particle size distribution curve and nearly monodisperse latex particles observed in the SEM images indicated that all LIPN particles were of nanoscale size, without evidence for new nucleation occurrence. TEM images demonstrated that latex particles had clearly core-shell structures. It also showed that most of the OMMt clay platelets were encapsulated in the polymer latex particles. According to the tan delta-temperature curve, addition of 0.5 wt% OMMt to the core layer improved the damping properties of the LIPN, while MMt could not affect the damping curve significantly. The results indicated that the diffusion of polymer chains into the OMMt clay galleries has increased the internal friction and so improved the damping properties.