Abstract
A flame retardant rigid polyurethane foam (RPUF) system containing functionalized graphene oxide (fGO), expandable graphite (EG), and dimethyl methyl phosphonate (DMMP) was prepared and investigated. The results show that the limiting oxygen index (LOI) of the flame-retardant-polyurethane-fGO (FRPU/fGO) composites reached 28.1% and UL-94 V-0 rating by adding only 0.25 g fGO. The thermal degradation of FRPU samples was studied using thermogravimetric analysis (TG) and the Fourier transform infrared (FT-IR) analysis. The activation energies (Ea) for the main stage of thermal degradation were obtained using the Kissinger equation. It was found that the fGO can considerably increase the thermal stability and decrease the flammability of RPUF. Additionally, the Ea of FRPU/fGO reached 191 kJ·mol−1, which was 61 kJ·mol−1 higher than that of the pure RPUF (130 kJ·mol−1). Moreover, scanning electron microscopy (SEM) results showed that fGO strengthened the compactness and the strength of the “vermicular” intumescent char layer improved the insulation capability of the char layer to gas and heat.
Highlights
Rigid polyurethane foam (RPUF) is a porous material, and has good shock absorption, low water absorption, low thermal conductivity, and high compressive strength [1,2,3,4]
Gavgani et al reported that graphene oxide (GO), working synergistically with the intumescent flame retardant (IFR) polyurethane, improved the burning behavior of composites [24], and the results showed that employing 2 wt % GO along with 18 wt % IFR (IFR/RPUF composite) obtained the limiting oxygen index (LOI) value of 34.0 and UL-94
According to the above description, it was shown that the thermal stability of flame retardant systems, especially of functionalized graphene oxide (fGO), significantly increased due to nanomaterials in both the air and nitrogen atmospheres during their thermal degradations
Summary
Rigid polyurethane foam (RPUF) is a porous material, and has good shock absorption, low water absorption, low thermal conductivity, and high compressive strength [1,2,3,4]. Many scientists believed that graphene and its derivatives were potential flame retardants with good flame retardation performance They along with conventional flame retardant fillers are a promising way to apply to flame retardant polyurethane [22,23,24,25,26,27]. Gavgani et al reported that graphene oxide (GO), working synergistically with the intumescent flame retardant (IFR) polyurethane, improved the burning behavior of composites [24], and the results showed that employing 2 wt % GO along with 18 wt % IFR (IFR/RPUF composite) obtained the limiting oxygen index (LOI) value of 34.0 and UL-94. FRPU/fGO composite was successfully prepared and the results showed that the flame-retardancy and mechanical properties of the composite dramatically improved. The effects of graphene oxide and functionalized graphene oxide on the thermal properties and flame retardation mechanism of the flame-retardant-polyurethane systems (FRPU) were investigated using thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM)
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