Fracture behavior-morphology relationships in an unsaturated polyester resin modified with a liquid oligomer

An unsaturated polyester (UP) resin modified with a liquid polymer, polyoxy propylenetriamine (POPTA), at a concentration of 10 wt% has been precured a t several temperatures. Phase separation takes place before gelation at all precure temperatures used. The glass-transition region has been analyzed b y dynamic mechanical analysis. Mechanical properties have been related to m icrostructural features. With a precure temperature fixed, the unsaturated polyester CUP) resin has also been modified with different contents of POPT A. Fracture toughness of the mixtures has also been analyzed and results ar e compared to those for the unmodified mixture. (C) 1999 John Wiley & Sons, Inc.