Preparation and properties of flame retardant rigid polyurethane foam with phosphorus–nitrogen intumescent flame retardant

Abstract

Ethanolamine spirocyclic pentaerythritol bisphosphonate (EMSPB), a novel intumescent flame retardant, was synthesized and used to improve the flame retardancy of rigid polyurethane foam (RPUF). The effects of EMSPB on the flammability, thermal stability, and mechanical properties of RPUF were discussed, respectively. Scanning electron microscopy (SEM) and compression strength tests showed that the EMSPB had favorable compatibility with the RPUF matrix and did not deteriorate the mechanical properties of the RPUF. Flammability of RPUF systems containing various contents of EMSPB was investigated by vertical burning test (UL-94) and limiting oxygen index (LOI) test. Results indicated that when the content of EMSPB was 25 wt%, the LOI of flame retardant RPUF could reach 27.5%, and a UL-94 V-0 rating was achieved. Thermogravimetric analysis showed that RPUF-containing EMSPB had a high yield of residual char at high temperatures, indicating that EMSPB was an effective charring agent. From the SEM observations of the residues of the flame retardant systems burned, the compact charred layers could be seen, which form protective shields to protect effectively the internal structure and inhibited the transmission of heat and heat diffusion during contacting fire.

Recent developments in P(O/S)–N containing flame retardants

“…RPUF was prepared with different concentrations of Compound 20 with the best fire results achieved at a loading of 25 wt % of 20 (i.e., V-0 rating in the UL-94 HB test and an LOI value of 27.5%). 74 Compound 20 was also incorporated in a waterborne PU (WPU) dispersion and its fire performance was evaluated. For the WPU matrix containing 9 wt % of 20, 1.62 wt % char content in TGA measurements were observed, and a higher LOI value of 26% was achieved.…”

“…116 In many cases, it is claimed that P(O)-N compounds offer synergism and improved flame retardancy of cellulose. [116][117][118] A series of alkyl ester phosphoramidates derivative (69)(70)(71)(72)(73)(74)(75) as shown in figure 20 were synthesized and incorporated in cellulose fibers obtained from a different source (peat and cotton fibers).…”

Flame‐retardant expandable polystyrene foams coated with ethanediol‐modified melamine–formaldehyde resin and microencapsulated ammonium polyphosphate

“…Despite the fact that adding flame retardants to styrene monomer before polymerization is regarded as a convenient method, the additive may interfere with the polymerization and cause a high concentration of residual styrene. In consideration of the diversity of flame retardants, researchers nowadays are inclined to choose the flame‐retardant coating applied during the foaming process as a promising solution . By this method, every EPS bead can be coated as an independent flame‐retardant structure unit, which provides excellent fire protection.…”

The flammability of expandable polystyrene foams coated with melamine modified urea formaldehyde resin

“…For EPS, coating with flame retardants has become a promising solution in consideration of the diversity of flame retardants and the simplicity of processing . Each EPS bead can be coated as an independent flame retardant structure unit, which can provide good flame retardant properties …”