(Fig. 14) was performed and indeed, a
corresponding signal at 4.3 ppm confirmed the presence of BPO4.
The signal at 12.5 ppm and the shoulder observed at
around 2.4 ppm were assigned to BO3 and BO4 [44]. As before,
chemical interaction between the AlPi and the adjuvant (ZB) was
proved. In effect, not only carbonaceous char coming from PPO is
formed, but also inorganic residue which provides an additional
barrier and stabilizes the char.31P(27Al) TRAPDOR experiments prove that for both
TPE-S/AlPi/MH and TPE-S/AlPi/ZB/PPO there is a chemical reaction
between additives. This synergistic interaction leads in effect to
formation of inorganic residue, which acts as a protective barrier
and improves fire behaviour.
Solid state NMR results for both systems with adjuvants,
TPE-S/AlPi/MH and TPE-S/AlPi/ZB/PPO, indicated that the formed
phosphates are partially crystalline (narrow signals). For that
reason the residues were additionally analysed by XRD