Influence of silica and coupling agent loading on thermal, morphological and mechanical properties of hybrid membranes

Hybrid polyetherimide-silica (PEI-SiO₂) membranes were synthesized via the sol–gel method through the hydrolysis of tetraethoxysilane (TEOS) with 3-aminopropyltriethoxysilane (APTEOS) as a coupling agent. The effects of silica content and the APTEOS/TEOS ratio in thermal, morphological and mechanical properties of the hybrid membranes were studied. Although many studies report improvements in the structure or properties of composite materials when a coupling agent is used, these contributions do not investigate the effect of the coupling agent loading on the properties of the new material synthesized. In this study, we prepared hybrid membrane with a fixed amount of APTEOS modifying TEOS content to analyze the silica content effect. Conversely, to determine the coupling agent effect, hybrid membranes were prepared varying the APTEOS content while the amount of TEOS was kept constant. All hybrid membranes have a dense and uniform internal structure and exhibit good thermal resistance with a degradation temperature above 544 °C. Membranes with 10 wt% of silica showed better tensile strength with a high modulus and low rupture elongation indicating an effective load transfer between the phases. Concerning the coupling agent effect, the maximum modulus was observed for membranes with 10 wt% of APTEOS, suggesting a greater interaction between the organic and inorganic phases.