Mechanical properties of 3-glycidoxypropyltrimethoxysilane based hybrid organic-inorganic materials

Hybrid organic-inorganic materials were synthesized from acid catalysed sol s of tetraethyl orthosilicate, 3-glycidoxypropyltrimethoxysilane and titani um or zirconium alkoxides. The mechanical properties of these materials wer e measured in different conditions of preparation. The elastic modulus E wa s determined by a resonance method and by Knoop microindentation. After a t hermal treatment at 125 degreesC for 120 h, E was around 3-5 and 1-2 GPa fo r the samples synthesized with titanium butoxide or zirconium butoxide, res pectively. An increase in E in the samples cured for longer times was obser ved. Knoop microhardness also increased with the heating time and was large r in samples synthesized from titanium alkoxides than zirconium alkoxides. The two methods gave results in good agreement when applied to samples trea ted for shorter times. In the other samples Knoop microindentation gave a l arger value of E compared to the resonance vibration method. Hardness to el astic modulus ratio, H/E, was evaluated by Knoop microindentation. The elas tic recovery at the longest heat treatment time was similar to that of soda -lime glasses. Fracture toughness was measured by three points flexural tes t, a K-Ic in the range of 0.4-0.5 MPa m(1/2) was evaluated for samples trea ted during 168 h.