Effect of the pressure on the crystallization behavior of polyamide 66

The crystallization behavior of polyamide 66 under high pressure up to 2500 bar was investigated by the use of dilatometric and calorimetric technique s in nonisothermal and isothermal conditions. The solid-solid Brill transit ion is detected from the evolution of the specific volume in the PVT diagra m. The variation of supercooling was examined under different pressures and temperatures. In nonisothermal conditions, when the same cooling rate is a pplied, the crystallization supercooling is not changed for different press ures. In isothermal conditions, for a given temperature, a pressure increas e extends the crystallization supercooling. By the analysis of melting peak s of samples crystallized in different conditions of pressure and temperatu re, we can conclude that the increasing of the crystallization supercooling leads to a decrease of the lamellae thickness. Finally, the evolution of t he thermodynamic equilibrium melting temperature according to pressure was examined. (C) 2001 John Wiley & Sons, Inc.