A phosphaphenanthrene groups containing soybean oil based polyol (DSBP) was synthesized
by epoxidized soybean oil (ESO) and 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide
(DOPO). Soybean oil based polyol (HSBP) was synthesized by ESO and H2O. The chemical structure
of DSBP and HSBP were characterized with FT-IR and 1H NMR. The corresponding rigid polyurethane
foams (RPUFs) were prepared by mixing DSBP with HSBP. The results revealed apparent density
and compression strength of RPUFs decreased with increasing the DSBP content. The cell structure
of RPUFs was examined by scanning electron microscope (SEM) which displayed the cells as spherical
or polyhedral. The thermal degradation and flame retardancy of RPUFs were investigated by thermogravimetric
analysis, limiting oxygen index (LOI), and UL 94 vertical burning test. The degradation
activation energy (Ea) of first degradation stage reduced from 80.05 kJ/mol to 37.84 kJ/mol with 80
wt% DSBP. The RUPF with 80 wt% DSBP achieved UL94 V-0 rating and LOI 28.3. The results
showed that the flame retardant effect was mainly in both gas phase and condensed phase.
Keywords: Soybean oil, ESO, DOPO, Polyurethane foam, Flame retardancy, RPUFs.
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