Augmenting thermal and mechanical properties of epoxy thermosets: The role of thermally-treated versus surface-modified TiO2 nanoparticles

Inorganic particulate reinforcements for organic epoxy resins and polymers attracted intense exploratory research in recent years to better the performance of existing composite materials and to devise new compositions of high performing materials. This work is aimed at investigating the role of crystalline and functional TiO2 nanoparticles in enhancing thermal and mechanical properties of epoxy thermosets. For this purpose, TiO2 nanoparticles are prepared and subjected to different processes, i.e., either thermal or surface chemical treatment, to obtain crystalline or functional TiO2 reinforcements differing in particle size, morphology, crystallinity, and surface chemistry. These TiO2 nanoparticles are subsequently embedded into epoxy matrix to form crystalline TiO2/epoxy (CTEN) or functional TiO2/epoxy (FTEN) nanocomposites with 2.5- 12.5 wt.% TiO2. Thus obtained nanocomposite are characterized by FTIR, SEM, DSC, TG, and static mechanical analyses. It is found that FTEN composites possess greater tensile strength (> 49%), fracture strength (> 64%), modulus (> 80%), toughness (> 35%), and T-g (> 48%) as compared to the reference epoxy polymer. CTEN composites, on the other hand, possess greater thermal stability. It is revealed that thermal decomposition temperature as well as final residual weight of CTEN composites are substantially increased by the presence of crystalline TiO2 nanoparticles. The optimum ratio of crystalline TiO2 nanoparticles for CTEN composites is found to be <= 5 wt.%, whereas the ratio of functional TiO2 nanoparticles for FTEN composites is <= 10.0 wt%, thus offering better performance of FTEN composites through appropriate processing of the inorganic reinforcements.