Novel synthesis with an atomized microemulsion technique and characterization of nano-calcium carbonate (CaCO3)/poly(methyl methacrylate) core-shell nanoparticles

The synthesis of hard-core/soft-shell calcium carbonate (CaCO3)/poly(methyl methacrylate) (PMMA) hybrid structured nanoparticles (<100 nm) by an atomized microemulsion polymerization process is reported. The polymer chains were anchored onto the surface of nano-CaCO3 through use of a coupling agent, triethoxyvinyl silane (TEVS). Ammonium persulfate (APS), sodium dodecyl sulfate (SDS) and n-pentanol were used as the initiator, surfactant and cosurfactant, respectively. The polymerization mechanism of the core-shell latex particles is discussed. The encapsulation of nano-CaCO3 by PMMA was confirmed using a transmission electron microscope (TEM). The grafting percentage of the core-shell particles was investigated by thermogravimetric analysis (TGA). The nano-CaCO3/PMMA core-shell particles were characterized by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The FTIR results revealed the existence of a strong interaction at the interface of the nano-CaCO3 particle and the PMMA, which implies that the polymer chains were successfully grafted onto the surface of the nano-CaCO3 particles through the link of the coupling agent. In addition, the TGA and DSC results indicated an enhancement of the thermal stability of the core-shell materials compared with that of the pure nano-PMMA. The nano-CaCO3/PMMA particles were blended into a polypropylene (PP) matrix by melt processing. It can also be observed using scanning electron microscopy (SEM) that the PMMA chains grafted onto the CaCO3 nanoparticles interfere with the aggregation of CaCO3 in the polymer matrix (PP matrix) and thus improve the compatibility of the CaCO3 nanoparticles with the PP matrix. (C) 2013 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.