THE INFLUENCE OF THE AMOUNT OF HARDENER ON THE TENSILE MECHANICAL-BEHAVIOR OF AN EPOXY SYSTEM

The tensile mechanical behavior of an epoxy/amine system, with varying amounts of hardener, was evaluated. The results showed that a brittle to ductile transition occurs as the amount of hardener is increased. This behavior was associated with the change in the number of molecula r segments that present mobility in the macromolecular network. The ep oxy-rich formulations are brittle due to the total consumption of the functional groups on the hardener molecule. On the other hand, the ami ne-rich formulations showed a fracture behavior characteristic of mate rials with large deformation capacity. This behavior was associated wi th the presence of unreacted points on the hardener molecule which int roduce a new mobile molecular segment in the macromolecular network fo rmed. (C) 1998 John Wiley & Sons, Ltd.