PREPARATION OF POLYMERIC NANOSILICA HYBRID MATERIALS AND THEIR PROPERTIES

This work relates to the development of polymeric nanosilica hybrid materials with nanosilica as node, IPDI and PPG as link and acrylate as terminal group for photopolymerization. The preparation process was as follow :nanosilica was first reacted with isophorone diisocyanate (IPDI), then extended the chain with polypropylene glycol (PPG) in proportion to the mole of NCO on the surface of silica, further terminated the left NCO groups with hydoxyethyl acrylate (HEA). Characterization of preparation by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) showed that IPDI, PPG and HEA were grafted onto nanosilica with chemical bonds and the percentage of grafting based on silica could be up to 92.2%. The morphology analysis of nanosilica and modified nanosilica by scanning electron microscopy (SEM) disclosed that modified nanosilica had lower aggregation and the diameters of silica particles were 30 50 nm although the sizes of nanosilica hybrid materials were beyond nanomaterial definition. Added 3% modified nanosilica into coating and compared with the coating with the same amount unmodified nanosilica, it was found that the viscosity of the coating decreased from 55 mPa.s to 48 mPa.s at 25 degrees C due to improvement of the compatibility of modified nanosilica with acrylic matrix, the conversion of C = C double bonds in coating increased at the same UV curing time because of modified nanosilica's better distributive performance in coating and lower scattering property for UV rays. After being cured, the pencil hardness of films increased from 3 H to 4 H and the weight loss decreased from 6.2 mg to 4.6 mg after 300 r/min abrasion due to a strong Si-O-Si bonding formed with network of film after polymeric nanosilica hybrid materials were used.