TY - JOUR
T1 - Oxidative and non-oxidative degradation of a TDI-based polyurethane foam
T2 - volatile product and condensed phase characterisation by FTIR and solid state 13C NMR spectroscopy
AU - Allan, D.
AU - Daly, J.
AU - Liggat, J.J.
PY - 2019/3/1
Y1 - 2019/3/1
N2 - The oxidative and non-oxidative degradation behaviour of a flexible polyurethane foam, synthesised from toluene diisocyanate and a polyether polyol, is reported. Both toluene diisocyanate and diaminotoluene were identified as major products under non-oxidative conditions, which indicates that the urethane linkages are degrading by two competing degradation mechanisms. Degradation of the urethane linkage by a depolymerisation reaction to yield toluene diisocyanate and polyol is proposed to occur initially. In addition, the atmospheric pressure conditions favour the degradation of the urethane linkages via a six-membered ring transition state reaction to form diaminotoluene, carbon dioxide and alkene terminated polyol chains. Solid-state 13C NMR spectroscopy and elemental analysis of the residues indicates that at temperatures above 300°C ring fusion of the aromatic components within the foam occurs, and this leads to a nitrogen-containing carbonaceous char which has a complex aromatic structure. It is proposed that under the confined conditions of the degradation the aromatic nitrogen-containing species, such as toluene diisocyanate and diaminotoluene, undergo secondary reactions and ring fusion to yield a complex char structureUnder oxidative conditions, degradation, including ring fusion, occurs
at a lower temperature than under non-oxidative conditions. Neither
toluene diisocyanate nor diaminotoluene were observed as major
degradation products. The polyol is observed to undergo thermo-oxidative
degradation at much lower temperatures than purely thermal degradation.
As a consequence, the depolymerisation reaction via the
six-membered ring transition state is limited in extent and
diaminotoluene is not evolved. The absence of toluene diisocyanate is
proposed to be a result of this species undergoing oxidative degradation
reactions which lead to it being incorporated into the char.
AB - The oxidative and non-oxidative degradation behaviour of a flexible polyurethane foam, synthesised from toluene diisocyanate and a polyether polyol, is reported. Both toluene diisocyanate and diaminotoluene were identified as major products under non-oxidative conditions, which indicates that the urethane linkages are degrading by two competing degradation mechanisms. Degradation of the urethane linkage by a depolymerisation reaction to yield toluene diisocyanate and polyol is proposed to occur initially. In addition, the atmospheric pressure conditions favour the degradation of the urethane linkages via a six-membered ring transition state reaction to form diaminotoluene, carbon dioxide and alkene terminated polyol chains. Solid-state 13C NMR spectroscopy and elemental analysis of the residues indicates that at temperatures above 300°C ring fusion of the aromatic components within the foam occurs, and this leads to a nitrogen-containing carbonaceous char which has a complex aromatic structure. It is proposed that under the confined conditions of the degradation the aromatic nitrogen-containing species, such as toluene diisocyanate and diaminotoluene, undergo secondary reactions and ring fusion to yield a complex char structureUnder oxidative conditions, degradation, including ring fusion, occurs
at a lower temperature than under non-oxidative conditions. Neither
toluene diisocyanate nor diaminotoluene were observed as major
degradation products. The polyol is observed to undergo thermo-oxidative
degradation at much lower temperatures than purely thermal degradation.
As a consequence, the depolymerisation reaction via the
six-membered ring transition state is limited in extent and
diaminotoluene is not evolved. The absence of toluene diisocyanate is
proposed to be a result of this species undergoing oxidative degradation
reactions which lead to it being incorporated into the char.
KW - polyurethane foam
KW - TDI
KW - solid state NMR
KW - condensed phase
KW - thermal degradation
KW - oxidation
UR - https://www.sciencedirect.com/journal/polymer-degradation-and-stability
U2 - 10.1016/j.polymdegradstab.2018.12.027
DO - 10.1016/j.polymdegradstab.2018.12.027
M3 - Article
SN - 0141-3910
VL - 161
SP - 57
EP - 73
JO - Polymer Degradation and Stability
JF - Polymer Degradation and Stability
ER -