A novel schiff base (BD) containing nitrogen and silicone
was prepared,
and a phosphorus–nitrogen silicone flame retardant (BDD) was
synthesized based on BD and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide
(DOPO). It was found that the structure of BD changed continuously
during the heating process and formed a self-cross-linking network
structure at about 400 °C, while the porous fluffy shape was
formed by BDD as an intumescent flame retardant. The char yields of
BD and BDD at 700 °C were 62% and 38% in nitrogen, respectively.
The obtained BD and BDD were blended to enhance the flame retardancy
of cellulose membranes via a cooperative effect, and the properties
were significantly achieved, which can be proved by the limit oxygen
index (LOI), cone calorimeter test, and thermogravimetric results.
The results showed that the incorporation of 25 wt % BD brought a
29% LOI, and the peak heat release rate (PHRR) was reduced to 732.2
kW/m2, in contrast with an LOI of 18% and PHRR of 1050.1
kW/m2 for pure cellulose. The addition of 25% BDD increased
the LOI to 27% and decreased the PHRR to 644.9 kW/m2. The
improved flame-retardant performance for cellulose membranes was primarily
assigned to the synergistic effect from the physical barriers of self-cross-linking
properties in the condensed phase and capturing or dilution of combustible
gases by free radicals. This suggested that wielding BD as a self-crossing
monomer and applying BDD as an intumescent flame retardant to achieve
effective results on fire suppression had great potential for fire-safe
cellulose.
A facile route was provided to prepare silicon/nitrogen synergistically reinforced flame-retardant PA6 nanocomposites with simultaneously improved anti-dripping and mechanical properties.
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