Structure and properties of LENRA/silica composite

The sol-gel reaction using tetraethoxysilane (TEOS) was conducted for modified natural rubber (NR) matrix to obtain in situ generated NR/silica composite. The present of acrylate group in the modified NR chain turns the composite into radiation-curable. The maximum amount of silica generated in the matrix was 50phr by weight. During the sol-gel process the inorganic mineral was deposited in the rubber matrix forming hydrogen bonding between organic and inorganic phases. The composites obtained were characterized by various techniques including thermogravimetric analysis and infrared spectrometry to study their molecular structure. The increase in mechanical properties was observed for low silica contents (<20phr) depending on the homogeneity of the filler in the rubber matrix. For higher contents of TEOS (>30phr) where more silica were generated, agglomerations were observed at the expense of the mechanical properties. From the DMTA data, it shows an increase of the interaction between the rubber and silica phases up to 30phr TEOS. Structure and morphology of the heterogeneous system were analyzed by transmission electron microscopy. The average particle sizes of between 150nm to 300nm were achieved for the composites that contain less than 20phr of TEOS.