Effects of an Acid Catalyst on the Inorganic Domain of Inorganic−Organic Hybrid Materials

Abstract

New inorganic−organic hybrid coatings have been developed using linseed oil and sunflower oil with the sol−gel precursor tetraethyl orthosilicate (TEOS). Hydrochloric acid (HCl) was used to catalyze the sol−gel reactions. The effects of HCl concentration on the morphology and distribution of the inorganic phase were investigated. Tensile properties, fracture toughness, thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA) of the ceramer coatings were evaluated as a function of acid catalyst concentration. In addition, scanning electron microscopy (SEM) and energy-dispersion X-ray analysis (EDAX) were used to investigate the morphology. The tensile properties showed an optimum acid concentration of 1.0 wt %. The fracture properties indicated that the greatest resistance to crack propagation was obtained with an acid concentration of 0.25 wt %. Thermogravimetric data showed that the thermal stability of the ceramer films increased with increasing acid catalyst. For TEOS/linseed ceramer films, storage modulus and tan δ data suggested that the acid catalyst promoted separation of the inorganic and organic phases. For TEOS/sunflower ceramer films, storage modulus and tan δ data suggested that the HCl promoted dispersion of the organic phase into the rigid inorganic phase.