An intumescent flame retardant containing caged bicyclic phosphate and oligomer: Synthesis, thermal properties and application in intumescent fire resistant coating

Abstract

An intumescent phosphorus-containing polyether (PAPEG) was synthesized by caged bicyclic phosphate 1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane (PEPA), phosphorus oxychloride (POCl3) and water soluble oligomer polyethylene glycol 200 (PEG200). Its structure was characterized by 1H nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). Turbiscan result confirmed that the solubility of PAPEG in water was improved when PEG200 was introduced. A possible thermal degradation mechanism of PAPEG was speculated according to the results of thermogravimetric analysis (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC) and real-time FTIR. Meanwhile, TG result indicated that graded decomposition of the two different kinds of phosphates in PAPEG were helpful for improving the charring efficiency of phosphorus. The transparent intumescent fire resistant coatings were prepared by melamine formaldehyde resin (MF) curing PAPEG. TG result showed that the residue weight increased first and then decreased with the increase of content of PAPEG. Fire protection test and SEM images illustrated that the PAPEG/MF fire resistant coatings could form thick foamed layers under flame and supplied effective fire protection for the substrates.