TIME-TEMPERATURE TRANSFORMATION (TTT) CURE DIAGRAM OF AN UNSATURATED POLYESTER RESIN

The curing of an unsaturated polyester resin was studied by differenti al scanning calorimetry (DSC), thermal mechanical analysis (TMA), and Fourier-transform infrared spectroscopy (FTIR). The results are presen ted in the form of a time-temperature-transformation (TTT) diagram. Th e kinetic analysis was performed by means of the dynamic Ozawa method. This analysis was used to determine the curing times (t) at various c onversions (alpha) and temperatures(T) (isoconversional lines In t = A + E/RT). The equivalence of the Ozawa method and the isothermal isoco nversional adjustment In t = A + E/RT were demonstrated. The relations hip between the glassy transition temperature (T-g) and the conversion alpha was determined by DSC. It was established that this relationshi p is one-to-one and independent of mass, initiation system, and curing temperature (T-g). The T-g-alpha relationship was adjusted using the DiBenedetto equations and heat capacity data. Using the T-g-alpha rela tionship and the isoconversional lines, the vitrification curve was de termined and it was observed that the vitrification times obtained are consistent with those obtained experimentally when T-c = T-g. Gelatio n was determined by TMA, the material being considered gelled when it reached sufficient mechanical stability for the TMA measuring probe to become embedded in it. At that moment the conversion reached was dete rmined by DSC. It was seen that the material always gels at constant c onversion, regardless of the curing temperature. The gelation line (ge l times) were traced from the corresponding isoconversional line. (C) 1997 John Wiley & Sons, Inc.