Facile Synthesis of a Highly Efficient, Halogen-Free,
and Intumescent Flame Retardant for Epoxy Resins: Thermal Properties,
Combustion Behaviors, and Flame-Retardant Mechanisms
posted on 2016-09-29, 00:00authored byChao Ma, Bin Yu, Ningning Hong, Yang Pan, Weizhao Hu, Yuan Hu
A novel
branched poly(phosphonamidate-phosphonate) (BPPAPO) oligomer
was synthesized from the polycondensation of phenylphosphonic dichloride
and trihydroxymethylphosphine oxide followed by
end-capping with aniline in a one-pot synthesis. BPPAPO exhibited
excellent flame-retardant efficiency in epoxy resins (EP). With only
5.0 wt % loading, the EP composite reached UL-94 V-0 rating with a
limiting oxygen index (LOI) value of 35.5%. BPPAPO catalyzed the early
degradation of EP and promoted the formation of more char residue.
Glass transition temperatures were partially lowered. When 7.5 wt
% BPPAPO was incorporated, the peak heat release rate and total heat
release were decreased by 66.2% and 37.3%, respectively, with a delayed
ignition and the formation of a highly intumescent char residue. Combination
of gas-phase and condensed-phase flame-retardant mechanisms was verified.