Thermal properties of epoxy–anhydride formulations cured using phosphonium accelerators

Synthesis of graphitic carbon nitride-based nanocomposites and their mechanical properties in epoxy compositions

Thermoset epoxy resins are widely used in research and commercial applications. Zeolite imidazole framework-8 (ZIF-8), graphitic carbon nitride (GCN, g-C3N4), and S-doped graphitic carbon nitride (SCN, S-g-C3N4) composites were synthesized as accelerators and their effects on the physical properties of epoxies were examined. An ultrasound-assisted method was used to prepare ZIF-8/GCN and ZIF-8/SCN nanocomposites while g-C3N4 and S-g-C3N4 were prepared from the calcination of melamine and thiourea, respectively. The surface morphology, and particle size were characterized by scanning electron microscopy, and X-ray diffraction. The properties of synthesized nanocomposites were measured using Fourier-transform infrared spectroscopy. After the accelerator was added to the epoxy composites, their activation energies were calculated using differential scanning calorimetry. The tensile strength and flexural strength were measured using a universal testing machine and impact strength was measured by using an Izod impact strength tester. The impact strength of ZIF-8/SCN nanocomposites was enhanced by 45.2%. The storage stability of the epoxy compositions with different catalysts was evaluated by measuring the variation of viscosity with time at a constant temperature.

Curing Regime-Modulating Insulation Performance of Anhydride-Cured Epoxy Resin: A Review

Anhydride-cured bisphenol-A epoxy resin is widely used in the support, insulation and sealing key components of electrical and electronic equipment due to their excellent comprehensive performance. However, overheating and breakdown faults of epoxy resin-based insulation occur frequently under conditions of large current carrying and multiple voltage waveforms, which seriously threaten the safe and stable operation of the system. The curing regime, including mixture ratio and combination of curing time and temperature, is an important factor to determine the microstructure of epoxy resin, and also directly affects its macro performances. In this paper, the evolution of curing kinetic models of anhydride-cured epoxy resin was introduced to determine the primary curing regime. The influences of curing regime on the insulation performance were reviewed considering various mixture ratios and combinations of curing time and temperature. The curing regime-dependent microstructure was discussed and attributed to the mechanisms of insulation performance.