Degradation profiles of cast films of polyurethane and poly(urethane-urea) aqueous dispersions based on hydroxy-terminated polybutadiene and different diisocyanates

New formulations of waterborne polyurethanes (wPU) and poly(urethane-urea)s (wPUU) were produced based on hydroxy-terminated polybutadiene (HTPB), poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), and three different types of aliphatic diisocyanates-isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (HMDI) and hexamethylene diisocyanate (HDI)-and the aromatic tolylene diisocyanate (TDI). Three types of chain extender were used in some of the formulations: ethylene glycol (EG), forming polyurethanes, and hydrazine (HYD) or ethylenediamine (EDA), resulting in poly(urethaneurea)s. In the formulations, HTPB content and NCO/OH ratio were varied. The thermal stability of the materials, obtained as cast films prepared from aqueous dispersions was evaluated by thermogravimetry (TG). It was observed that initial degradation temperatures were above 200 degreesC, with two- or three-step degradation profiles. An increase in HTPB content, the presence of urea linkages, and HMDI as diisocyanate in the formulations led to materials with higher thermal stability. DTG curves exhibited stages not perceptible in the curves of weight loss, which were mainly influenced by the differences in the formulations. (C) 2003 Elsevier Science Ltd. All rights reserved.