Smoke and toxicity suppression by zinc salts in flame‐retardant polyurethane‐polyisocyanurate foams filled with phosphonate and chlorinated phosphate

Abstract

Three types of zinc salts, ZnAl 2 O 4 , ZnFe 2 O 4, and Zn 2 SiO 4, were prepared by coprecipitation. Potential smoke and toxicity suppression by zinc salts in flame-retardant polyurethane-polyisocyanurate foams (FPUR-PIR) with dimethylmethylphosphonate (DMMP) and tris (2-chloropropyl) phosphate (TCPP) were investigated. The crystal structure and dispersity of zinc salts in FPUR-PIR were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Smoke density, flame retardancy, and thermal degradation were studied using smoke density rating (SDR), limiting oxygen index (LOI), the cone calorimeter test, and thermogravimetry coupled with FTIR spectrophotometry (TGA-FTIR). The results indicated that pure zinc salts were obtained and evenly dispersed on the cell wall of FPUR-PIR. SDR and the specific extinction area (SEA) were significantly decreased, the time to second heat release rate peak (pk-HRR) of FRUP-PIR was delayed after incorporation of the zinc salts; zinc salts partially inhibited phosphorus oxide release into the gas phase, enhanced the condensed phase effect of phosphorus, reduced, and prolonged the release of isocyanate compound and hydrogen cyanide from FRUP-PIR; due to an increase in the amount of char residues, which indicated the suppression of smoke and toxicity volatiles. ZnFe 2 O 4 resulted in better char formation at the initial degradation stage of FPUR-PIR, and ZnAl 2 O 4 retained more phosphorus in the solid phase at higher temperature.

Thermal decomposition and flammability of rigid PU foams containing some DOPO derivatives and other phosphorus compounds

“…For 13 C NMR data multiplicities s = quaternary carbon, d = CH, t = CH 2 , and q = CH 3 are shown and 31 P, 13 C coupling constants are reported in Hz. 13 → H-(10); H-13 → H- (14); H-14 → H- (13); NHa → NHb; NHb → NHa. 31…”

“…However, the use of halogencontaining flame retardants is restricted in some applications because of their toxicity [11,12]. The use of TCPP results in an increase in the smoke toxicity of polyurethane as large amount of toxic and corrosive gases such as CO and HCl are released during the combustion process [10,13], which are not conducive to evacuation and rescue operations. To substitute the halogenated flame retardants, development of new and efficient environment friendly halogen-free flame retardants are needed.…”

Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin

“…A great effort has been made to improve the physicochemical properties of PUR–PIR foams. Boro‐organic compounds, borate, aluminum hydroxide, expandable graphite, phosphonates, and zinc salts are used as fillers to improve the thermal and flame retardance of PUR–PIR foam . However, a low content of fillers gives rise to limited improvement of flame retardancy, whereas a high content causes high viscosity and poor mechanical properties …”

Flame retardant plasticized poly(vinyl chloride) film with selective solar spectral transparent properties

“…In addition, PO$ produced by the decomposition of TCPP can catch H$, HO$ and then interrupt the chain reaction of combustion (see reactions (5)-(8)). 16 These also contributes to the higher ame-retardance. …”