Phosphorus-Containing polyurethanes based on bisphenol-AF, prepared by N-alkylation
✍ Scribed by Der-Jang Liaw; Shiuh-Ping Lin
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 393 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Phosphorus-containing polyurethanes (PU-P) based on bisphenol-AF were synthesized by N-alkylation in a two-step process. First, the polymer was metalated with sodium hydride; then the prepared urethane polyanion was treated with diethyl 2-bromoethyl phosphate.
IR spectra exhibited characteristic absorptions a t 1303 cm-' ( P = O stretch), 1015 cm-' 0 / \ (PO-C stretch), 960 cm-' (POC-C stretch), 812 cm-' (P deform), 2912-3020 cm-' 0 (CH stretch), 1646 cm-' ( C = O stretch), 1231 cm-' (CNH), and 1053 cm-' (CO-0-C stretch). In the 'H-NMR spectrum of the maximum substituted PU-P, the signal of the urethane proton (NU -CO -0) at 9.87 ppm virtually disappeared as expected; new signals appeared a t 1.20-1.24 ppm ( P O C H a 3 ) and 3.79 ppm (PO=,CH,).
Physical and thermal properties of the N-alkylated polymer were also investigated with differential scanning calorimetry (DSC), solubility, X-ray diffraction, thermogravimetric analysis (TGA), limiting oxygen index (LOI), and reduced viscosity. DSC analysis showed that T, values were decreased from 81 to 43OC. The reduced viscosities of the PU-Ps were observed in the range of 0.23-0.18 dL g-'. The results of TGA revealed that the thermal stability was decreased, because the phosphorus moiety in the PUS is readily dissociated thermally. The PU-Ps exhibited enhanced fire resistance because phosphorus simultaneously promoted carbonization of the polymer and inhibited combustion. The X-ray diffraction patterns of the PU-Ps showed that with increasing phosphorus content, the degree of crystallinity of the PUS decreased. N-alkylated PUS are soluble, not only in polar solvents such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and H,SO,, but also in less polar solvents such as phenol, toluene, THF, and trichloroethylene.