Recent Developments in the Flame-Retardant System of Epoxy Resin

With the increasing emphasis on environmental protection, the development of flame retardants for epoxy resin (EP) has tended to be non-toxic, efficient, multifunctional and systematic. Currently reported flame retardants have been capable of providing flame retardancy, heat resistance and thermal stability to EP. However, many aspects still need to be further improved. This paper reviews the development of EPs in halogen-free flame retardants, focusing on phosphorus flame retardants, carbon-based materials, silicon flame retardants, inorganic nanofillers, and metal-containing compounds. These flame retardants can be used on their own or in combination to achieve the desired results. The effects of these flame retardants on the thermal stability and flame retardancy of EPs were discussed. Despite the great progress on flame retardants for EP in recent years, further improvement of EP is needed to obtain numerous eco-friendly high-performance materials.

Synthesis and properties of cycloaliphatic epoxy resins containing imide and diphenyl sulfone

A novel variety of cycloaliphatic epoxy resins containing imide and diphenyl sulfone (named as 4,4′-bis[4-(4,5-epoxy-1,2,3,6-tetrahydro-phthalimido) phenoxy] diphenyl sulfone, BIES) is designed and synthesized through the three-step procedure. The mixtures of BIES and diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate (TDE-85) are cured with methyl tetrahydrophthalic anhydride. Fourier transform infrared spectrum and proton nuclear magnetic resonance spectrum confirm that the BIES contains the chemical structure of imide and diphenyl sulfone. The measurements of glass transition temperature ( Tg), heat distortion temperature (HDT), and the 5% weight loss temperature ( T5%) show that the co-cured BIES/TDE-85 exhibits excellent heat resistance. For the BIES/TDE-85 with mass ratio of 0.2, Tg, HDT, and T5% of the co-cured epoxy are 175°C, 162°C, and 290°C, respectively. The impact strength increases from 117 J m−1 to 139 J m−1 with the increasing of the mass ratios of the BIES/TDE-85 from 0 to 0.2.