Surface functionalized boehmite sheets filled epoxy composites with enhanced mechanical and thermal properties

Short- and Long-Range Mechanical and Chemical Interphases Caused by Interaction of Boehmite (γ-AlOOH) with Anhydride-Cured Epoxy Resins

Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands.

Effect of functionalization of multi-walled carbon nanotube on mechanical and viscoelastic properties of polysulfide-modified epoxy nanocomposites

In order to obtain epoxy compounds with excellent mechanical properties without compromising other desired properties, pristine- or carboxyl-functionalized multi-walled carbon nanotube (p-MWCNT or f-MWCNT) along with polysulfide were incorporated into an amine-cured epoxy resin. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses proved the existence of carboxyl groups on the surface of f-MWCNT. Adding 0.1 wt% f-MWCNT significantly improved the tensile strength and impact strength of the epoxy nanocomposites by 104% and 47%, respectively. However, adding p-MWCNT had little effect on the mechanical properties of the nanocomposites. The glass transition temperature of the f-MWCNT/epoxy nanocomposites were also much higher than neat epoxy matrix and p-MWCNT/epoxy nanocomposites. The fracture surface morphology and dynamic mechanical analysis results indicated that the interfacial interactions between f-MWCNT and the epoxy matrix were much stronger than that of p-MWCNT, which ensured the much-improved mechanical properties.