Shuang Yang,Siqi Huo,Jun Wang,Bin Zhang,Jingsheng Wang,Shiya Ran,Zhengping Fang,Pingan Song,Hao Wang
The design of highly fire-safe and smoke-suppressive single-component epoxy (EP) resins combining modest curing temperature and fast curing rate has been desirable yet very challenging in both academia and industry. Herein, we report a facile design of a phosphorus/imidazole-containing single-component EP system via incorporating 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and a flame-retardant curing agent cyclotriphosphazene-modified benzimidazole (BICP) into EP. Our results show that EP/DOPO/BICP exhibits a rapid modest-temperature curing feature because DOPO serves as a switch that triggers BICP to release benzimidazole (BIM) via substitution reaction in the initial curing stage. Moreover, as-prepared EP/DOPO/BICP shows outstanding fire retardancy, reflected by the high limited oxygen index (LOI) of 38.3% and UL-94 V-0 rating. Compared to the control EP system, the peak of heat release rate (PHRR) and total smoke production (TSP) of EP/DOPO/BICP remarkably decrease by ~74.5% and ~50.6%, respectively, which is superior to previously-reported flame-retardant P-containing epoxy counterparts. The significant enhancements in flame retardancy and smoke suppression are mainly due to the formation of a highly intumescent char layer and the reduced burning degree of pyrolysis fragments. This work offers a facile and scalable strategy for creating fast-curing, modest-temperature curable, highly fire-resistant and smoke-suppressive one-component epoxy systems applicable to large-scale industrial production.
To simplify the manufacture and address the intrinsic flammability of epoxy resin (EP) products, the single-component, fire-safe EP systems are increasingly in demand. However, current design strategy is difficult to achieve the simultaneous improvement in storage stability, flame retardancy and smoke suppression. Herein, a phosphorus/imidazole-containing, aluminum-based complex (ADIM) was synthesized, and applied as a latent curing agent for EP. The shelf life of EP/ADIM system reached 30 days, and its gel time at 150 °C was only 42 min, indicative of great thermal latency and fast curing rate. EP/ADIM thermoset showed superior flame retardancy, as confirmed by a limiting oxygen index (LOI) of 35.0% and a UL-94 V-0 classification. In addition, the total smoke production and maximum smoke density of EP/ADIM thermoset were 38.7% and 22.3% lower than those of EP thermoset cured by imidazole (EP/IM), demonstrating obviously-enhanced smoke suppression. ADIM inhibited the heat release and smoke generation of the EP matrix via radical capturing and catalytic charring. Moreover, EP/ADIM thermoset exhibited comparable thermal resistance and mechanical properties to EP/IM thermoset. Hence, this work offers an integrated design strategy for creating high-performance, fire-safe, single-component EP with well-preserved mechanical and thermal properties.
In this work, the synthesis of simple and convenient flame retardant curing agents for epoxy resin (EP) was investigated to solve the problems of existing flame retardant curing agents due to their complicated preparation process and poor mechanical properties. In this paper, a new type of ionic liquid curing agent (ZIM) was successfully synthesized by introducing a one-step reaction between n-octylphosphoric acid (OPA), which contains a flexible chain, and imidazole (IM) at room temperature. The results showed that the curing agent had a gel time of only 3.5 min at 120 °C, and could achieve UL94 V-0 rating with an ultimate oxygen index of 32 % or more at any additive amount of 15 phr or more. The peak exothermic rate and total exothermic rate are reduced by 55.45 % and 33.45 %, which can meet the requirements of fire safety standards in the industrial field. In addition, the incorporation of flexible chain segments and the absorption of energy dissipation by ionic bonding resulted in a 118.33 % increase in elongation at break and 127.44 % increase in impact strength of EP/ZIM-15, which greatly improved the mechanical properties. This work provides an efficient and simple method for preparing high performing EP curing agents.
危险品化学品经营许可证（带存储）