Effect of silicon and phosphorus on the degradation of polyurethanes

Abstract

A series of polyurethanes containing silicon and phosphorus was prepared from 4,4′-diphenylmethane diisocyanate (MDI), poly(tetramethylene ether glycol) (PTMG), diphenylsilanediol (DSiD), and methylphosponic acid (MPA). 1H-NMR spectra determined the qualitative and quantitative characteristics of these polymers. The thermal stability and activation energy for thermal degradation of these polymers were measured by thermogravimtry and compared with pure polyurethane (PU). The DSiD incorporated into the main chain of the polymer improved the thermal stability of PU, while the phosphorus-containing polyurethane (P–PU) displayed a lower thermal stability than that of pure PU. The activation energies at various degradation stages for the pure PU, silicon-containing polyurethane (Si–PU), and P–PU polymers were calculated by the Ozawa method. The activation energies of the Si–PU polymers were higher than were those of pure PU and increased according to the increase in the DSiD content. However, the P–PU polymers' activation energies were smaller than were those of pure PU, and they decreased with increasing phosphorus content in the range of 0.1 ≤ conversion ≤ 0.5, whereas the reverse was true between 0.6 and 0.9. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 881–899, 2001