AbstractThe approach of free radical polymerization is adapted to develop a kinetic model for predicting the curing behavior of unsaturated polyester resins. The approach taken here is essentially similar to that advanced by Stevenson with some modifications, namely (1) the efficiency of the initiator is assumed to decrease with conversion, (2) no assumption was made a priori on the magnitude of the rate constants for the termination and inhibition reactions, and (3) the propagation rate constant was assumed to be represented bykp=Aoexp(−Ep/RT) ˙1 − (α/αf)m, and the termination rate constant bykt=Boexp( −Et/RT)1 ‐ (α/αf)n, in whichAoandBoare preexponential constants,EpandEtare the activation energies for the propagation and termination reactions, respectively,Ris the universal gas constant,Tis the absolute temperature, α is the degree of conversion, αfis the final degree of conversion, andmandnare constants to be determined by numerical simulation. A computer program was developed to search for the optimal values of all the parameters involved, to minimize the difference between the predicted and experimentally determined rate of conversion and the degree of conversion simultaneously. An experimental study was also conducted on the cure of unsaturated polyester resin, using differential scanning calorimetry (DSC) under isothermal conditions and infrared (IR) spectroscopy. The degree of cure was determined from the total heat generated during cure, with the aid of the IR spectra of the residual double bonds in the cured resin. The predictability of the mechanistic model developed is presented and the usefulness of the model for simulating various processing operation
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