Cure kinetics, morphology and miscibility of modified DGEBA-based epoxy resin – Effects of a liquid rubber inclusion

Experimental modeling of the cure kinetics of an epoxy-hexaanhydro-4-methylphthalicanhydride (MHHPA) system

Stoichiometric mixtures of DGEBA (diglycidyl ether of bisphenol A)/DDS (diaminodiphenyl sulfone) and DGEBA/mPDA (meta phenylene diamine) have been isothermally cured by electromagnetic radiation and conventional heating using thin film sample configurations. Fourier transform infrared spectroscopy (FTIR) was used to measure the extent of cure. Thermal mechanical analysis (TMA) was used to determine the glass transition temperatures directly from the cured thin film samples. Well-defined glass transitions were observed in the TMA thermograph for both thermal and microwave cured samples. Significant increases in the reaction rates have been observed in the microwave cured DGEBA/DDS samples. Only slight increases in the reaction rates have been observed in the microwave cured DGEBA/mPDA samples. Higher glass transition temperatures were obtained in microwave cured samples compared to those of thermally cured ones after gelation. The magnitude of increases of glass transition temperature is much larger for the DGEBA/DDS system than DGEBA/mPDA system. The microwave radiation effect was much more significant in DGEBA/DDS system than in DGEBA/mPDA system. DiBenedetto's model was used to fit the experimental Tg data of both thermal and microwave cured epoxy resins.

Comparison of microwave and thermal cure of epoxy resins

Three-dimensional laser microfabrication blends microscopy, optical nonlinear phenomena, photomodification, laser trapping, and creates novel possibilities for fabrication of micro- and nano-struct...

Three-Dimensional Micro-and Nano-Structuring of Materials by Tightly Focused Laser Radiation

The cross-linking kinetics and the rheological behavior of a polyurethane system during curing are investigated by DSC and small amplitude oscillatory shear rheometry. In this study, isoconversional methods are applied to understand the reaction complexity. The activation energy depends on the extent of conversion. It can be shown that three parallel reactions occur during the evolution of the global reaction in non-isothermal conditions. An original multi-step model can involve these three parallel independent reactions. Dynamic viscosity is measured as a function of time and is found independent of shear rate. Isothermal viscosity rise is related to reaction extent by a phenomenological model. The gelation time is determined by the tanδ crossover at different frequencies. Polym. Eng. Sci. 44:518–527, 2004. © 2004 Society of Plastics Engineers.

Curing kinetics and chemorheological analysis of polyurethane formation

Synopsis An analysis of the cure kinetics of several different formulations composed of bifunctional epoxy resins and aromatic diamines was performed. A series of isothermal differential scanning calorimetry (DSC) runs (at higher temperature) and Fourier transform infrared spectroscopy (FT-IR) runs (at lower temperature) provided information about the kinetics of cure in the temperature range 18-160°C. All kinetic parameters of the curing reaction, including the reaction rate order, activation energy, and frequency factor were calculated and reported. Dynamic and isothermal DSC yielded different results. An explanation was offered in terms of different curing mechanisms which prevail under different curing conditions. A mechanism scheme was proposed to account for various possible reactions during cure.

Antonio Moroni

Papers

Cure kinetics of epoxy resins and aromatic diamines