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Journal of Nanomaterials
Volume 2012, Article ID 263915, 8 pages
Research Article

Functionalization of Silica Nanoparticles for Polypropylene Nanocomposite Applications

Departamento de Ingeniería Química y Biotecnología, FCFM, Universidad de Chile, 850 Beauchef, 8370448 Santiago, Chile

Received 14 May 2012; Accepted 8 August 2012

Academic Editor: Sergio J. Mejía-Rosales

Copyright © 2012 Diego Bracho et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Synthetic silica nanospheres of 20 and 100 nm diameter were produced via the sol-gel method to be used as filler in polypropylene (PP) composites. Modification of the silica surface was further performed by reaction with organic chlorosilanes in order to improve the particles interaction with the hydrophobic polyolefin matrix. These nanoparticles were characterized using transmission electronic microscopy (TEM), elemental analysis, thermogravimetric analysis (TGA), and solid-state nuclear magnetic resonance (NMR) spectroscopy. For unmodified silica, it was found that the 20 nm particles have a greater effect on both mechanical and barrier properties of the polymeric composite. In particular, at 30 wt%, Young's modulus increases by 70%, whereas water vapor permeability (WVP) increases by a factor of 6. Surface modification of the 100 nm particles doubles the value of the composite breaking strain compared to unmodified particles without affecting Young's modulus, while 20 nm modified particles presented a slight increase on both Young's modulus and breaking strain. Modified 100 nm particles showed a higher WVP compared to the unmodified particles, probably due to interparticle condensation during the modification step. Our results show that the addition of nanoparticles on the composite properties depends on both particle size and surface modifications.