Highly efficient fire retardant behavior, thermal stability, and physicomechanical properties of rigid polyurethane foam based on recycled poly(ethylene terephthalate)

摘要

This study focused on the burning phenomena, thermal stability, and physicomechanical properties of polyurethane foam based on recycled poly(ethylene terephthalate) (RPUF) with and without halogen-free flame retardants (FRs). Flammability behavior and associated mechanisms were studied by cone calorimetry, LOI, UL 94, FTIR, TGA, FE-SEM, and XPS. The results of cone calorimeter testing indicate improved FR performance with notable reductions in peak heat release rate (39.1%), peak CO production (61.7%), and peak CO2 production (43.0%). LOI values significantly increase, up to 29.5-47.1%, in the presence of FRs, and V-0 ratings are attained even at a rather low loading of FR (6.07 wt%). Meanwhile, the RPUF completely burns to the holder clamp with a low LOI value (17%), and it do not pass the UL94 HB standard. The addition of FRs notably improves the residual char of RPUF, indicating that FRs contributed to the formation of a barrier layer to protect RPUF during degradation. The comparison between experimentally determined TGA results and calculated values provides support for the effect of FRs on the thermal degradation behavior of RPUF. Sorption isotherm experiments of RPUF/FR systems show low moisture absorptivity and a weak hysteresis effect due to strong intermolecular bonds between RPUF and added FRs. The compression test, density, and morphology of foam samples are also discussed.