AbstractA new polythiourethane thermosetting system based on a diisocyanate and a trithiol was studied. After characterization of the reactive species, two critical temperatures, namely Tg∞ (maximum glass transition temperature of the thermosetting system) and gelTg (Tg of the material at the gel point), were determined. The conversion at gel point was also determined and compared to the theoretical prediction. Two different characteristics of the evolution of a reactive system, Tg and conversion x as a function of time, were related. This is of particular interest for understanding the curing process, especially when non-isothermal cure schedules are used. Viscoelastic and plastic properties were investigated, with the aim of establishing connections between the chemical structure and properties through detailed analysis of the polymer chain motions (β and α relaxations). Measurements of the storage modulus at the rubbery plateau and of the critical strain intensity factor KIc complete the study.
