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To simultaneously improve the storage stability of epoxy/imidazole systems and flame retardancy without sacrificing the thermal, mechanical and dielectric properties of thermosets, a novel multifunctional polyetherimide containing benzimidazole and phosphorus (mPI) was synthesized and used as a hardener for diglycidyl ether of bisphenol A (DGEBA). In addition to retaining the effective curing behavior of imidazole, mPI, a macromolecular hardener and flame retardant, could endow the mixture of DGEBA and mPI (EP/mPI) with the long latent period and thermosets with the high performance. The results showed that mPI was unreactive at ambient temperature and underwent the rapid curing reaction at 170 °C that is a little higher than its glass transition temperature (T g) of 164.7 °C, and EP/mPI showed the long thermal latent period of 70 days or more. Meanwhile, the cured EP/mPI attained the UL-94 V-0 rating with the LOI value of 31.2%. Besides, EP/mPI thermoset showed a 42.9 °C, 47.6 °C, 18.2 °C, 135.4% and 60.6% increase in the T g , heat deflection temperature, temperature at 5% mass loss, storage modulus and Young's modulus, respectively, as well as a 3.6% decrease in the dielectric constant at 100 MHz, in comparison with those of the traditional cured DGEBA/benzimidazole (EP/BIM). This work provides a facile strategy to prepare one-pot epoxy/imidazole formulations and flame-retarded epoxy thermosets with high performance by using the well-designed multifunctional polyetherimides as a hardener and flame retardant, which has good application prospects in electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

The aggregation and plasticizing of most 9,10-dihydro-9-oxa-10-phosphaphenanthrene −10-oxide (DOPO) derived additives often result in deteriorating the glass transition temperature and mechanical properties of epoxy resins (EP). To address this issue, an imide-DOPO derivative (BMP) with bulky aromatic structure was successfully synthesized. Benefitting from the space hindering and intermolecular interaction (π-π stacking) of BMP, it does not lead to the loss of glass transition temperature, and only a minor damage of tensile and impact strengths is caused. Additionally, with only 0.78 wt% loading of phosphorus (10 wt% BMP), the EP/BMP 10% achieves UL-94 V-0 and high LOI value of 35%. Simultaneously, both the heat release rate and total smoke production are markedly reduced. More excitingly, BMP exhibits aggregation-induced emission enhancement of fluorescence in the N, N -dimethylformamide/water mixed solution as well as epoxy resin. This work provides a new insight in simultaneously imparting flame retardancy and fluorescence to epoxy resins without losing glass transition temperature. [Display omitted] • Imide-DOPO derivative exhibits aggregation-induced emission enhancement. • Imide-DOPO derivative endows epoxy resin with excellent flame retardancy. • No loss of T g while the improvement of flame retardancy. • Fluorescence is imparted to the flame retardant epoxy resin. [ABSTRACT FROM AUTHOR]

Epoxy resins (EPs) are a kind of widely used engineering materials, because of their excellent mechanical, chemical and physical properties, but a severe problem they faced is their poor flame retardancy. Single molecule flame retardants have met the bottleneck after the massive researches of the past decade, so, with the development of the polymer technology, hyperbranched flame retardants have been researched and applied, owing to their better and more efficient flame retardancy. Herein, a facile thermal treating procedure was applied to the cured EP thermosets which contained a crosslinkable additive flame retardant to in-situ form a hyperbranched flame retardant. The single molecule flame retardants with N/P elements and crosslinkable nitrile groups were synthesized through an easy method, and physically mixed with EP matrix. After the curing reaction of EP matrix, the thermosets were further treated with a thermal treating procedure, while transferring the single molecule flame retardant into hyperbranched flame retardant, the semi-interpenetrating network was formed at the same time. The flame-retardant properties have been measured by limiting oxygen index (LOI) tests, UL-94 vertical burning tests and cone calorimeter tests, the results showed the flame retardants were extremely efficient and greatly elevated the flame retardancy of EPs, since the 0.5 wt% content could make modified EP samples pass the UL-94 V-0 rate, and with 20 wt% content the LOI value reached 49.5 % and the peak heat release rate reduced for 71.6 % compared with pure EPs. [ABSTRACT FROM AUTHOR]