Preparation of a novel Fe-MOF as the flame retardant synergist and its application in polystyrene

In this work, a metal organic framework (Fe-MOF) with the effect of absorbing toxic gases and good compatibility was synthesized by chelating a novel organic ligand contained carbonization groups (reacted by tris(hydroxymethyl) aminomethane and 1,4-piperazine dialdehyde) with iron salt. Then, it was used as the synergist to improve the efficiency of intumescent flame retardant (IFR) within polystyrene (PS) substrate. With the addition of 20% IFR and 2% Fe-MOF, the obtained PS composites exhibited a limiting oxygen index (LOI) value of 28.3% and a UL rating of V-0. Moreover, the peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) of PS composites were decreased by 77.6%, 35.2%, and 33.7%, respectively. According to the mechanism analysis, it was found that Fe-MOF mainly acted in the condensed phase, contributing to the existence of dense char residues with the presence of IFR system. In addition, the good compatibility of organic ligand in Fe-MOF with PS substrate could partially alleviate the deterioration of mechanical properties due to the addition of IFR. For PS-20%IFR/2%Fe-MOF, the impact strength was improved from 1.7 kJ/m(2) (PS-22%IFR) to 2.2 kJ/m(2), the tensile strength was also increased from 21.3 MPa (PS-22%IFR) to 22.4 MPa.