Abstract
A hyperbranched phosphorus-containing copper phthalocyanine compound (DOPO-CuPc) was successfully synthesized and used as the flame-retardant additive to prepare flame-retarded epoxy thermosets. The addition of DOPO-CuPc led to a significant enhancement of the flame retardant properties of the epoxy resin. The 15DOPO-CuPc/EP composite obtained a LOI value of 35.8%, and the UL-94 rose from NR to V-0 rating. And the addition of DOPO-CuPc resulted in early decomposition of the epoxy thermoset, but the residual char at 700 °C reached 27.7%. The flame retardant mechanism was further investigated. It was found that DOPO-CuPc could release phosphorus-containing radicals and non-combustible gases in the gas phase to exert gas-phase flame retardant activity. In the condensed phase, the epoxy thermoset formed the expanded honeycomb-like char layer during combustion and the presence of copper phthalocyanine contributed to the stability of the char layer.
Highlights
A hyperbranched phosphorus-containing copper phthalocyanine compound (DOPO-CuPc) was successfully synthesized and used as the flame-retardant additive to prepare flame-retarded epoxy thermosets
The results showed that the limiting oxygen index (LOI) of TEBA increased by about 64% compared to the original epoxy resin and the UL-94 rating was improved from no rating to V-0
The new appeared peaks at 1055/cm and 1657/cm were attributed to the metal–ligand (Cu–N) vibration[21] and phthalocyanine
Summary
A hyperbranched phosphorus-containing copper phthalocyanine compound (DOPO-CuPc) was successfully synthesized and used as the flame-retardant additive to prepare flame-retarded epoxy thermosets. The addition of DOPO-CuPc led to a significant enhancement of the flame retardant properties of the epoxy resin. Zhu et al designed a novel phosphorus-nitrogen containing oligomer (BPOPA) as an additive to enhance the flame retardancy of epoxy resin/ammonium polyphosphate[14]. Phthalocyanines, a hyperbranched organic macromolecular compound with dendritic molecular structure, have attracted attention for their unique two-dimensional coplanar aromatic heterocyclic structure[16,17] This special conjugate structure imparts exceptional thermal and chemical stability to the phthalocyanine. The flame retardant properties and thermal stability of the modified epoxy thermosets were evaluated by flammability tests, and the flame retardant mechanism of DOPO-CuPc was analyzed
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