Using silica nanoparticles as curing reagents for epoxy resins to form epoxy-silica nanocomposites

Long-Term Performance of Nanomodified Coated Concrete Structures under Hostile Marine Climate Conditions

Epoxy resin coatings are commonly used to protect concrete structures due to their excellent chemical corrosion resistance and strong adhesion capacity. However, these coatings are susceptible to damage by surface abrasion and long-term contact with marine climate conditions, deteriorating their appearance and performance. This study aims to optimize the performance of cement-based epoxy resin coatings, bisphenol-A and polyol, in aggressive environments by functionalizing the selected systems with different nanoparticles such as activated carbon, surface modified nanoclay, silica and zinc oxide. Nanomodified coatings were applied to concrete specimens and subjected to three weeks in a spray salt chamber and three weeks in a QUV chamber. They were found to present improved thermal resistance and curing degree after the weathering test. Their water permeability, adhesion, and abrasion resistance properties were evaluated before and after this test. The results showed that the nature of the nanocomposites determined their water permeability; the bare resin presented the worst result. Additionally, nanomodified composites with activated carbon and silica showed the best adherence and abrasion resistance properties, due to the effect of this aging test on their thermal stability and curing degree.

Remarkable enhancement of thermal stability of epoxy resin through the incorporation of mesoporous silica micro-filler

For the first time, we incorporated mesoporous micro-silica (5 μm, pore size = 50 nm) as a filler in epoxy resin aiming to enter polymer into the pore of the silica. As expected, the thermal stability of the composite increased remarkably, followed by noteworthy thermal degradation kinetics when compared to the controlled cured epoxy resin. Composites were prepared by the direct dispersion of modified nano-silica, modified mesoporous micro-silica, unmodified mesoporous micro-silica, non-porous micro-silica, and irregular micro-silica of various pore sizes as fillers in diglycidyl ether of bisphenol-A epoxy resin via ultra-sonication and shear mixing, followed by oven-curing with 4,4-diaminodiphenyl sulfone. DSC and TGA analyses demonstrated a higher glass transition temperature (increased by 3.65–5.75 °C) and very high activation energy for thermal degradation (average increase = 46.2%) was obtained for the same unmodified silica composite compared to pure epoxy, respectively.

Modifying the carbon fiber–epoxy matrix interphase with silicon dioxide nanoparticles

The carbon fiber surface was modified by silicon dioxide nanoparticles by immersing CFs tows in a SiO₂ nanoparticle suspension. A significant increase of the IFSS was obtained.